Publications – Peer-Reviewed Journal Articles
| Title: | Demonstration of ensemble data assimilation for Mars using DART, MarsWRF, and radiance observations from MGS TES |
| Authors: | Lee, C; Lawson, W. G.; Richardson, M. I.; Anderson, J. L.; Collins, N.; Hoar, T.; and Mischna, M. |
| Affiliation: | |
| Journal: | Journal of Geophysical Research, Vol. 116 |
| Publication Date: | Nov 2011 |
| Origin: | |
| Abstract Copyright: | |
| DOI: | |
| Bibliographic Code: | |
| Abstract: | We describe a global atmospheric data assimilation scheme that has been adapted for use with a Martian General Circulation Model (GCM), with the ultimate goal of creating globally and temporally interpolated “reanalysis” data sets from planetary atmospheric observations. The system uses the Data Assimilation Research Testbed (DART) software to apply an Ensemble Kalman Filter (EnKF) to the MarsWRF GCM. Specific application to Mars also required the development of a radiance forward model for near‐nadir Thermal Emission Spectrometer (TES) observations. Preliminary results from an assimilation of 40 sols of TES radiance data, taken around Ls = 150° (August 1999, Mars Year 24), are provided. 1.3 million TES observations are ingested and used to improve the state prediction by the GCM, with bias and error reductions obtained throughout the state vector. Results from the assimilation suggest steepening of the latitudinal and vertical thermal gradients with concurrent strengthening of the mid‐latitude zonal jets, and a slower recession of the southern polar ice edge than predicted by the unaided GCM. Limitations of the prescribed dust model are highlighted by the presence of an atmospheric radiance bias. Preliminary results suggest the prescribed dust vertical profile might not be suitable for all seasons, in accordance with more recent observations of the vertical distribution of dust by the Mars Climate Sounder. The tools developed using this DA system are available at http://www.marsclimatecenter.com. A tutorial and example TES radiance assimilation are also provided. |
| Title: | Curvilinear features in the southern hemisphere observed by Mars Global Surveyor Mars Orbiter Camera |
| Authors: | Wang, Huiqun; Toigo, Anthony D.; Richardson, Mark I. |
| Affiliation: | AA(Atomic and Molecular Physics, Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138, USA), AB(Center for Radiophysics and Space Research, 326 Space Sciences Building, Cornell University, Ithaca, NY 14853, USA; Present address: Johns Hopkins University, Applied Physics Laboratory, Laurel, MD 20723, USA.), AC(Ashima Research, Pasadena, CA 91106, USA) |
| Journal: | Icarus, Volume 215, Issue 1, p. 242-252. |
| Publication Date: | Sep 2011 |
| Origin: | ELSEVIER |
| Abstract Copyright: | Elsevier Inc. |
| DOI: | http://dx.doi.org/10.1016/j.icarus.2011.06.029 |
| Bibliographic Code: | 2011Icar..215..242W |
| Abstract: | We have used the complete set of Mars Global Surveyor (MGS) Mars Daily Global Maps (MDGMs) to study martian weather in the southern hemisphere, focusing on curvilinear features, including frontal events and streaks. “Frontal events” refer to visible events that are morphologically analogous to terrestrial baroclinic storms. MDGMs show that visible frontal events were ainly concentrated in the 210–300°E (60–150°W) sector and the 0–60°E sector around the southern polar cap during Ls = 140–250° and Ls = 340–60°. The non-uniform spatial and temporal distributions of activity were also shown by MGS Thermal Emission Spectrometer transient temperature variations near the surface. “Streaks” refer to long curvilinear features in the polar hood or over the polar cap. They are an indicator of the shape of the polar vortex. Streaks in late winter usually show wavy segments between the 180° meridian and Argyre. Model results suggest that the zonal wave number m = 3 eastward traveling waves are important for their formation. |
| Title: | A Discrete Ordinate, Multiple Scattering, Radiative Transfer Model of the Venus Atmosphere from 0.1 to 260μm |
| Authors: | Lee, Christopher; Richardson, Mark Ian |
| Journal: | Journal of the Atmospheric Sciences, vol. 68, issue 6, pp. 1323-1339 |
| Publication Date: | Jun 2011 |
| Origin: | CROSSREF |
| DOI: | http://dx.doi.org/10.1175/2011JAS3703.1 |
| Bibliographic Code: | 2011JAtS…68.1323L |
| Abstract: | Not Available |
| Title: | Stratospheric superrotation in the TitanWRF model |
| Authors: | Newman, Claire E.; Lee, Christopher; Lian, Yuan; Richardson, Mark I.; Toigo, Anthony D. |
| Affiliation: | AA(Ashima Research, Suite 104, 600 South Lake Avenue, Pasadena, CA 91106, USA), AB(Ashima Research, Suite 104, 600 South Lake Avenue, Pasadena, CA 91106, USA), AC(Ashima Research, Suite 104, 600 South Lake Avenue, Pasadena, CA 91106, USA), AD(Ashima Research, Suite 104, 600 South Lake Avenue, Pasadena, CA 91106, USA), AE(The Johns Hopkins University, Applied Physics Laboratory, 11100 Johns Hopkins Road, Laurel, MD 20723, USA) |
| Journal: | Icarus, Volume 213, Issue 2, p. 636-654. |
| Publication Date: | Jun 2011 |
| Origin: | ELSEVIER |
| Abstract Copyright: | Elsevier Inc. |
| DOI: | http://dx.doi.org/10.1016/j.icarus.2011.03.025 |
| Bibliographic Code: | 2011Icar..213..636N |
| Abstract: | TitanWRF general circulation model simulations performed without sub-grid-scale horizontal diffusion of momentum produce roughly the observed amount of superrotation in Titan’s stratosphere. We compare these results to Cassini-Huygens measurements of Titan’s winds and temperatures, and predict temperature and winds at future seasons. We use angular momentum and transformed Eulerian mean diagnostics to show that equatorial superrotation is generated during episodic angular momentum ‘transfer events’ during model spin-up, and maintained by similar (yet shorter) events once the model has reached steady state. We then use wave and barotropic instability analysis to suggest that these transfer events are produced by barotropic waves, generated at low latitudes then propagating poleward through a critical layer, thus accelerating low latitudes while decelerating the mid-to-high latitude jet in the late fall through early spring hemisphere. Finally, we identify the dominant waves responsible for the transfers of angular momentum close to northern winter solstice during spin-up and at steady state. Problems with our simulations include peak latitudinal temperature gradients and zonal winds occurring ˜60 km lower than observed by Cassini CIRS, and no reduction in zonal wind speed around 80 km, as was observed by Huygens. While the latter may have been due to transient effects (e.g. gravity waves), the former suggests that our low (˜420 km) model top is adversely affecting the circulation near the jet peak, and/or that we require active haze transport in order to correctly model heating rates and thus the circulation. Future work will include running the model with a higher top, and including advection of a haze particle size distribution. |
| Title: | The vertical distribution of dust in the Martian atmosphere during northern spring and summer: Observations by the Mars Climate Sounder and analysis of zonal average vertical dust profiles |
| Authors: | Heavens, N. G.; Richardson, M. I.; Kleinböhl, A.; Kass, D. M.; McCleese, D. J.; Abdou, W.; Benson, J. L.; Schofield, J. T.; Shirley, J. H.; Wolkenberg, P. M. |
| Affiliation: | AA(Division of the Geological and Planetary Sciences, California Institute of Technology, Pasadena, California, USA), AB(Ashima Research, Pasadena, California, USA), AC(Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California, USA), AD(Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California, USA), AE(Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California, USA), AF(Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California, USA), AG(Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California, USA), AH(Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California, USA), AI(Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California, USA), AJ(Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California, USA) |
| Journal: | Journal of Geophysical Research, Volume 116, Issue E4, CiteID E04003 |
| Publication Date: | Apr 2011 |
| Origin: | AGU |
| Keywords: | Planetary Sciences: Solar System Objects: Mars, Atmospheric Composition and Structure: Aerosols and particles (0345, 4801, 4906), Atmospheric Composition and Structure: Planetary atmospheres (5210, 5405, 5704), Atmospheric Processes: General circulation (1223), Atmospheric Processes: Global climate models (1626, 4928) |
| Abstract Copyright: | (c) 2011: American Geophysical Union |
| DOI: | http://dx.doi.org/10.1029/2010JE003691 |
| Bibliographic Code: | 2011JGRE..11604003H |
| Abstract: | The vertical distribution of dust in Mars’s atmosphere is a critical and poorly known input in atmospheric physical and chemical models and a source of insight into the lifting and transport of dust and general vertical mixing in the atmosphere. We investigate vertical profiles of dust opacity retrieved from limb observations by Mars Climate Sounder during the relatively dust-clear Martian northern summer of 2006-2007 (Ls = 111°-177°of Mars year (MY) 28) and Martian northern spring and summer of 2007-2008 (Ls = 0°-180° of MY 29). To represent local maxima in inferred mass mixing ratio in these profiles, we develop an empirical alternative to the classic “Conrath profile” for representing the vertical distribution of dust in the Martian atmosphere. We then assess the magnitude and variability of atmospheric dust loading, the depth of dust penetration during these seasons, and the impact of the observed vertical dust distribution on the radiative forcing of the circulation. During most of northern spring and summer, the dust mass mixing ratio in the tropics has a maximum at 15-25 km above the local surface (the high-altitude tropical dust maximum (HATDM)). The HATDM appears to have increased significantly in magnitude and altitude during middle to late northern summer of MY 29. The HATDM gradually decayed during late summer of MY 28. Interannual variability in the dust distribution during middle to late northern summer may be connected with known interannual variability in tropical dust storm activity. |
| Title: | Atmospheric modeling of Mars methane surface releases |
| Authors: | Mischna, Michael A.; Allen, Mark; Richardson, Mark I.; Newman, Claire E.; Toigo, Anthony D. |
| Affiliation: | AA(Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Dr., M/S 183-401, Pasadena, CA 91109, USA), AB(Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Dr., M/S 183-401, Pasadena, CA 91109, USA; Also, Division of Geological and Planetary Sciences, California Institute of Technology, MC 150-21, 1200 E. California Blvd. Pasadena, CA 91125, USA), AC(Division of Geological and Planetary Sciences, California Institute of Technology, MC 150-21, 1200 E. California Blvd. Pasadena, CA 91125, USA; Present address: Ashima Research, 600 S. Lake Ave, Suite 303, Pasadena, CA 91106, USA), AD(Division of Geological and Planetary Sciences, California Institute of Technology, MC 150-21, 1200 E. California Blvd. Pasadena, CA 91125, USA; Present address: Ashima Research, 600 S. Lake Ave, Suite 303, Pasadena, CA 91106, USA), AE(Cornell University, Department of Astronomy, Ithaca, NY 14853, USA; Present address: The Johns Hopkins University, Applied Physics Laboratory, 11100 Johns Hopkins Rd., Laurel, MD 20723, USA) |
| Journal: | Planetary and Space Science, Volume 59, Issue 2-3, p. 227-237. |
| Publication Date: | Feb 2011 |
| Origin: | ELSEVIER |
| Abstract Copyright: | Elsevier Ltd |
| DOI: | http://dx.doi.org/10.1016/j.pss.2010.07.005 |
| Bibliographic Code: | 2011P&SS…59..227M |
| Abstract: | We utilize the MarsWRF general circulation model (GCM) to address the behavior of gas plumes in the Martian atmosphere, with the specific goal of characterizing the source of the recently identified methane detection in the Martian atmosphere. These observations have been interpreted as the release of methane from localized surface sources with spatial and temporal variabilities. Due to the limited temporal coverage of ground-based observations, we use a GCM to simulate the development of passive atmospheric plumes over relevant timescales. The observations can be reproduced best if the release occurred just before the time of observation—no more than 1-2 sols earlier—and if this release were nearly instantaneous rather than a slow, steady emission. Furthermore, it requires a source region spanning a broad latitudinal range rather than a point emission. While the accuracy of our conclusions about this specific methane release scenario is limited by the uncertainties inherent in GCM simulations of the Martian atmosphere, our findings regarding generalized plume behavior are robust, and illustrate the potential power of numerical modeling for constraining plume source conditions. |
| Title: | Structure and dynamics of the Martian lower and middle atmosphere as observed by the Mars Climate Sounder: 2. Implications of the thermal structure and aerosol distributions for the mean meridional circulation |
| Authors: | Heavens, N. G.; McCleese, D. J.; Richardson, M. I.; Kass, D. M.; Kleinböhl, A.; Schofield, J. T. |
| Affiliation: | AA(Division of the Geological and Planetary Sciences, California Institute of Technology, Pasadena, California, USA); AB(Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California, USA); AC(Ashima Research, Pasadena, California, USA); AD(Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California, USA); AE(Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California, USA); AF(Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California, USA) |
| Journal: | Journal of Geophysical Research, Volume 116, Issue E1, CiteID E01010 |
| Publication Date: | Jan 2011 |
| Origin: | AGU |
| Keywords: | Atmospheric Composition and Structure: Planetary atmospheres (5210, 5405, 5704), Atmospheric Processes: General circulation (1223), Atmospheric Processes: Mesospheric dynamics, Planetary Sciences: Solar System Objects: Mars |
| Abstract Copyright: | (c) 2011: American Geophysical Union |
| DOI: | http://dx.doi.org/10.1029/2010JE003713 |
| Bibliographic Code: | 2011JGRE..11601010H |
| Abstract: | Retrievals of temperature, dust, and water ice from data collected by the Mars Climate Sounder (MCS) on Mars Reconnaissance Orbiter (MRO) illustrate for the first time the seasonal and diurnal variability of both the thermal structure of the middle atmosphere (above 40 km) and also the vertical distribution of aerosols. These retrievals reveal clear signatures of significant mean meridional cells in the middle and lower atmosphere at both the solstices and equinoxes. We investigate the degree to which the lower and middle atmospheric circulations are kinematically coupled and conclude that kinematic coupling is strong in the tropics throughout the year but weak near the pole except during the “polar warming” events associated with dust storm activity. |
| Title: | Vertical distribution of dust in the Martian atmosphere during northern spring and summer: High-altitude tropical dust maximum at northern summer solstice |
| Authors: | Heavens, N. G.; Richardson, M. I.; Kleinböhl, A.; Kass, D. M.; McCleese, D. J.; Abdou, W.; Benson, J. L.; Schofield, J. T.; Shirley, J. H.; Wolkenberg, P. M. |
| Affiliation: | AA(Division of the Geological and Planetary Sciences, California Institute of Technology, Pasadena, California, USA); AB(Ashima Research, Pasadena, California, USA); AC(Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California, USA); AD(Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California, USA); AE(Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California, USA); AF(Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California, USA); AG(Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California, USA); AH(Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California, USA); AI(Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California, USA); AJ(Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California, USA) |
| Journal: | Journal of Geophysical Research, Volume 116, Issue E1, CiteID E01007 |
| Publication Date: | Jan 2011 |
| Origin: | AGU |
| Keywords: | Planetary Sciences: Solar System Objects: Mars, Atmospheric Composition and Structure: Aerosols and particles (0345, 4801, 4906), Atmospheric Composition and Structure: Planetary atmospheres (5210, 5405, 5704), Atmospheric Processes: Convective processes, Atmospheric Processes: Global climate models (1626, 4928) |
| Abstract Copyright: | (c) 2011: American Geophysical Union |
| DOI: | http://dx.doi.org/10.1029/2010JE003692 |
| Bibliographic Code: | 2011JGRE..11601007H |
| Abstract: | The vertical distribution of dust in Mars’ atmosphere is a critical unknown in the simulation of its general circulation and a source of insight into the lifting and transport of dust. Zonal average vertical profiles of dust opacity retrieved by Mars Climate Sounder show that the vertical dust distribution is mostly consistent with Mars general circulation model (GCM) simulations in southern spring and summer but not in northern spring and summer. Unlike the GCM simulations, the mass mixing ratio of dust has a maximum at 15-25 km over the tropics during much of northern spring and summer: the high-altitude tropical dust maximum (HATDM). The HATDM has significant and characteristic longitudinal variability, which it maintains for time scales on the order of or greater than those on which advection, sedimentation, and vertical eddy diffusion would act to eliminate both the longitudinal and vertical inhomogeneity of the distribution. While outflow from dust storms is able to produce enriched layers of dust at altitudes much greater than 25 km, tropical dust storm activity during the period in which the HATDM occurs is likely too rare to support the HATDM. Instead, the lifting of dust by mesoscale circulations over topography, pseudomoist convection due to the solar heating of dust, and scavenging of dust by water ice are all possible drivers of the HATDM. |
| Title: | Structure and dynamics of the Martian lower and middle atmosphere as observed by the Mars Climate Sounder: Seasonal variations in zonal mean temperature, dust, and water ice aerosols |
| Authors: | McCleese, D. J.; Heavens, N. G.; Schofield, J. T.; Abdou, W. A.; Bandfield, J. L.; Calcutt, S. B.; Irwin, P. G. J.; Kass, D. M.; Kleinböhl, A.; Lewis, S. R.; Paige, D. A.; Read, P. L.; Richardson, M. I.; Shirley, J. H.; Taylor, F. W.; Teanby, N.; Zurek, R. W. |
| Affiliation: | AA(Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California, USA); AB(Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, California, USA); AC(Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California, USA); AD(Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California, USA); AE(Department of Atmospheric Sciences, University of Washington, Seattle, Washington, USA); AF(Department of Physics, University of Oxford, Oxford, UK); AG(Department of Physics, University of Oxford, Oxford, UK); AH(Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California, USA); AI(Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California, USA); AJ(Department of Physics and Astronomy, Open University, Milton Keynes, UK); AK(Department of Earth and Space Sciences, University of California, Los Angeles, California, USA); AL(Department of Physics, University of Oxford, Oxford, UK); AM(Ashima Research, Pasadena, California, USA); AN(Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California, USA); AO(Department of Physics, University of Oxford, Oxford, UK); AP(Department of Physics, University of Oxford, Oxford, UK); AQ(Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California, USA) |
| Journal: | Journal of Geophysical Research, Volume 115, Issue E12, CiteID E12016 |
| Publication Date: | Dec 2010 |
| Origin: | AGU |
| Keywords: | Planetary Sciences: Solar System Objects: Mars |
| Abstract Copyright: | (c) 2010: American Geophysical Union |
| DOI: | http://dx.doi.org/10.1029/2010JE003677 |
| Bibliographic Code: | 2010JGRE..11512016M |
| Abstract: | The first Martian year and a half of observations by the Mars Climate Sounder aboard the Mars Reconnaissance Orbiter has revealed new details of the thermal structure and distributions of dust and water ice in the atmosphere. The Martian atmosphere is shown in the observations by the Mars Climate Sounder to vary seasonally between two modes: a symmetrical equinoctial structure with middle atmosphere polar warming and a solstitial structure with an intense middle atmosphere polar warming overlying a deep winter polar vortex. The dust distribution, in particular, is more complex than appreciated before the advent of these high (˜5 km) vertical resolution observations, which extend from near the surface to above 80 km and yield 13 dayside and 13 nightside pole-to-pole cross sections each day. Among the new features noted is a persistent maximum in dust mass mixing ratio at 15-25 km above the surface (at least on the nightside) during northern spring and summer. The water ice distribution is very sensitive to the diurnal and seasonal variation of temperature and is a good tracer of the vertically propagating tide. |
| Title: | THEMIS-VIS observations of clouds in the martian mesosphere: Altitudes, wind speeds, and decameter-scale morphology |
| Authors: | McConnochie, T. H.; Bell, J. F.; Savransky, D.; Wolff, M. J.; Toigo, A. D.; Wang, H.; Richardson, M. I.; Christensen, P. R. |
| Affiliation: | AA(Department of Astronomy, University of Maryland, College Park, MD 20742, USA), AB(Department of Astronomy, Cornell University, Ithaca, NY 14853, USA), AC(Department of Mechanical and Aerospace Engineering, Princeton University, Princeton, NJ 08544, USA), AD(Space Science Institute, 4750 Walnut Street, Suite 205, Boulder, CO 80301, USA), AE(Applied Physics Laboratory, Johns Hopkins University, Laurel, MD 20723, USA), AF(Harvard-Smithsonian Center for Astrophysics, Cambridge, MA 02138, USA), AG(Division of Geological and Planetary Sciences, California Institute of Technology, 1200 E. California Blvd, Pasadena, CA 91125, USA; Ashima Research, Pasadena, CA 91106, USA), AH(Department of Geological Sciences, Arizona State University, Tempe, AZ 85287, USA) |
| Journal: | Icarus, Volume 210, Issue 2, p. 545-565. |
| Publication Date: | Dec 2010 |
| Origin: | ELSEVIER |
| Abstract Copyright: | Elsevier Inc. |
| DOI: | http://dx.doi.org/10.1016/j.icarus.2010.07.021 |
| Bibliographic Code: | 2010Icar..210..545M |
| Abstract: | We present measurements of the altitude and eastward velocity component of mesospheric clouds in 35 imaging sequences acquired by the Mars Odyssey (ODY) spacecraft’s Thermal Emission Imaging System visible imaging subsystem (THEMIS-VIS). We measure altitude by using the parallax drift of high-altitude features, and the velocity by exploiting the time delay in the THEMIS-VIS imaging sequence. We observe two distinct classes of mesospheric clouds: equatorial mesospheric clouds observed between 0° and 180°Ls; and northern mid-latitude clouds observed only in twilight in the 200-300°Ls period. The equatorial mesospheric clouds are quite rare in the THEMIS-VIS data set. We have detected them in only five imaging sequences, out of a total of 2048 multi-band equatorial imaging sequences. All five fall between 20° south and 0° latitude, and between 260° and 295° east longitude. The mid-latitude mesospheric clouds are apparently much more common; for these we find 30 examples out of 210 northern winter mid-latitude twilight imaging sequences. The observed mid-latitude clouds are found, with only one exception, in the Acidalia region, but this is quite likely an artifact of the pattern of THEMIS-VIS image targeting. Comparing our THEMIS-VIS images with daily global maps generated from Mars Orbiter Camera Wide Angle (MOC-WA) images, we find some evidence that some mid-latitude mesospheric cloud features correspond to cloud features commonly observed by MOC-WA. Comparing the velocity of our mesospheric clouds with a GCM, we find good agreement for the northern mid-latitude class, but also find that the GCM fails to match the strong easterly winds measured for the equatorial clouds. Applying a simple radiative transfer model to some of the equatorial mesospheric clouds, we find good model fits in two different imaging sequences. By using the observed radiance contrast between cloud and cloud-free regions at multiple visible-band wavelengths, these fits simultaneously constrain the optical depths and particles sizes of the clouds. The particle sizes are constrained primarily by the relative contrasts at the available wavelengths, and are found to be quite different in the two imaging sequences: reff = 0.1 μm and reff = 1.5 μm. The optical depths (constrained by the absolute contrasts) are substantial: 0.22 and 0.5, respectively. These optical depths imply a mass density that greatly exceeds the saturated mass density of water vapor at mesospheric temperatures, and so the aerosol particles are probably composed mainly of CO2 ice. Our simple radiative transfer model is not applicable to twilight, when the mid-latitude mesospheric clouds were observed, and so we leave the properties of these clouds as a question for further work. |
| Title: | Water ice clouds over the Martian tropics during northern summer |
| Authors: | Heavens, N. G.; Benson, J. L.; Kass, D. M.; Kleinböhl, A.; Abdou, W. A.; McCleese, D. J.; Richardson, M. I.; Schofield, J. T.; Shirley, J. H.; Wolkenberg, P. M. |
| Affiliation: | AA(Division of the Geological and Planetary Sciences, California Institute of Technology, Pasadena, California, USA); AB(Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California, USA); AC(Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California, USA); AD(Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California, USA); AE(Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California, USA); AF(Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California, USA); AG(Ashima Research, Pasadena, California, USA); AH(Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California, USA); AI(Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California, USA); AJ(Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California, USA) |
| Journal: | Geophysical Research Letters, Volume 37, Issue 18, CiteID L18202 |
| Publication Date: | Sep 2010 |
| Origin: | AGU |
| Keywords: | Planetary Sciences: Solar System Objects: Mars, Atmospheric Composition and Structure: Cloud physics and chemistry, Atmospheric Composition and Structure: Cloud/radiation interaction, Atmospheric Processes: Clouds and cloud feedbacks, Atmospheric Processes: General circulation (1223) |
| Abstract Copyright: | (c) 2010: American Geophysical Union |
| DOI: | http://dx.doi.org/10.1029/2010GL044610 |
| Bibliographic Code: | 2010GeoRL..3718202H |
| Abstract: | Atmospheric models suggest that infrared heating due to water ice clouds over the tropics of Mars during early northern summer has a significant impact on the thermal structure of the tropics at cloud level and of the middle atmosphere near the south pole. Retrievals from limb observations by the Mars Climate Sounder on Mars Reconnaissance Orbiter during early northern summer show that water ice clouds over the northern tropics are thinner and higher than in published model results. Later in this season, the latitudinal extent, apparent mass mixing ratio (and infrared heating rate), and altitude of nighttime tropical clouds significantly increase, reaching a maximum just before northern fall equinox. Published model results do not show this transition. By underestimating the altitude at which water ice clouds form, models also may underestimate the intensity of the meridional circulation at higher altitudes in the tropics during northern summer. |
| Title: | Convective instability in the martian middle atmosphere |
| Authors: | Heavens, N. G.; Richardson, M. I.; Lawson, W. G.; Lee, C.; McCleese, D. J.; Kass, D. M.; Kleinböhl, A.; Schofield, J. T.; Abdou, W. A.; Shirley, J. H. |
| Affiliation: | AA(Division of Geological and Planetary Sciences, California Institute of Technology, MC 150-21, Pasadena, CA 91125, USA), AB(Division of Geological and Planetary Sciences, California Institute of Technology, MC 150-21, Pasadena, CA 91125, USA; Ashima Research, 600 S. Lake Ave., Pasadena, CA 91106, USA), AC(Division of Geological and Planetary Sciences, California Institute of Technology, MC 150-21, Pasadena, CA 91125, USA), AD(Division of Geological and Planetary Sciences, California Institute of Technology, MC 150-21, Pasadena, CA 91125, USA; Ashima Research, 600 S. Lake Ave., Pasadena, CA 91106, USA), AE(Jet Propulsion Laboratory, California Institute of Technology, Mail Stop 183-501, 4800 Oak Grove Dr., Pasadena, CA 91109, USA), AF(Jet Propulsion Laboratory, California Institute of Technology, Mail Stop 183-501, 4800 Oak Grove Dr., Pasadena, CA 91109, USA), AG(Jet Propulsion Laboratory, California Institute of Technology, Mail Stop 183-501, 4800 Oak Grove Dr., Pasadena, CA 91109, USA), AH(Jet Propulsion Laboratory, California Institute of Technology, Mail Stop 183-501, 4800 Oak Grove Dr., Pasadena, CA 91109, USA), AI(Jet Propulsion Laboratory, California Institute of Technology, Mail Stop 183-501, 4800 Oak Grove Dr., Pasadena, CA 91109, USA), AJ(Jet Propulsion Laboratory, California Institute of Technology, Mail Stop 183-501, 4800 Oak Grove Dr., Pasadena, CA 91109, USA) |
| Journal: | Icarus, Volume 208, Issue 2, p. 574-589. |
| Publication Date: | Aug 2010 |
| Origin: | ELSEVIER |
| Abstract Copyright: | Elsevier Inc. |
| DOI: | http://dx.doi.org/10.1016/j.icarus.2010.03.023 |
| Bibliographic Code: | 2010Icar..208..574H |
| Abstract: | Dry convective instabilities in Mars’s middle atmosphere are detected and mapped using temperature retrievals from Mars Climate Sounder observations spanning 1.5 martian years. The instabilities are moderately frequent in the winter extratropics. The frequency and strength of middle atmospheric convective instability in the northern extratropics is significantly higher in MY 28 than in MY 29. This may have coupled with changes to the northern hemisphere mid-latitude and tropical middle atmospheric temperatures and contributed to the development of the 2007 global dust storm. We interpret these instabilities to be the result of gravity waves saturating within regions of low stability created by the thermal tides. Gravity wave saturation in the winter extratropics has been proposed to provide the momentum lacking in general circulation models to produce the strong dynamically-maintained temperature maximum at 1-2 Pa over the winter pole, so these observations could be a partial control on modeling experiments. |
| Title: | On the mystery of the perennial carbon dioxide cap at the south pole of Mars |
| Authors: | Guo, Xin; Richardson, Mark Ian; Soto, Alejandro; Toigo, Anthony |
| Affiliation: | AA(Planetary Science, Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, California, USA); AB(Ashima Research, Pasadena, California, USA); AC(Planetary Science, Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, California, USA); AD(Center for Radiophysics and Space Research, Cornell University, Ithaca, New York, USA) |
| Journal: | Journal of Geophysical Research, Volume 115, Issue E4, CiteID E04005 |
| Publication Date: | Apr 2010 |
| Origin: | AGU |
| Keywords: | Atmospheric Composition and Structure: Planetary atmospheres (5210, 5405, 5704), Planetary Sciences: Solar System Objects: Mars, Planetary Sciences: Solid Surface Planets: Polar regions, Planetary Sciences: Solid Surface Planets: Atmospheres (0343, 1060), Planetary Sciences: Solid Surface Planets: Ices |
| DOI: | http://dx.doi.org/10.1029/2009JE003382 |
| Bibliographic Code: | 2010JGRE..11504005G |
| Abstract: | A perennial ice cap has long been observed near the south pole of Mars. The surface of this cap is predominantly composed of carbon dioxide ice. The retention of a CO2 ice cap results from the surface energy balance of the latent heat, solar radiation, surface emission, subsurface conduction, and atmospheric sensible heat. While models conventionally treat surface CO2 ice using constant ice albedos and emissivities, such an approach fails to predict the existence of a perennial cap. Here we explore the role of the insolation-dependent ice albedo, which agrees well with Viking, Mars Global Surveyor, and Mars Express albedo observations. Using a simple parameterization within a general circulation model, in which the albedo of CO2 ice responds linearly to the incident solar insolation, we are able to predict the existence of a perennial CO2 cap at the observed latitude and only in the southern hemisphere. Further experiments with different total CO2 inventories, planetary obliquities, and surface boundary conditions suggest that the location of the residual cap may exchange hemispheres favoring the pole with the highest peak insolation. |
| Title: | A general circulation model ensemble study of the atmospheric circulation of Venus |
| Authors: | Lee, C.; Richardson, M. I. |
| Affiliation: | AA(Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, California, USA); AB(Ashima Research, Pasadena, California, USA) |
| Journal: | Journal of Geophysical Research, Volume 115, Issue E4, CiteID E04002 |
| Publication Date: | Apr 2010 |
| Origin: | AGU |
| Keywords: | Planetary Sciences: Solar System Objects: Venus, Atmospheric Processes: General circulation (1223), Planetary Sciences: Fluid Planets: Atmospheres (0343, 1060), Planetary Sciences: Solid Surface Planets: Atmospheres (0343, 1060), Planetary Sciences: Solid Surface Planets: Meteorology (3346) |
| DOI: | http://dx.doi.org/10.1029/2009JE003490 |
| Bibliographic Code: | 2010JGRE..11504002L |
| Abstract: | The response of three numerical model dynamical cores to Venus-like forcing and friction is described in this paper. Each dynamical core simulates a super-rotating atmospheric circulation with equatorial winds of 35 ± 10 m/s, maintained by horizontally propagating eddies leaving the equatorial region and inducing a momentum convergence there. We discuss the balance between the mean circulation and eddies with reference to the production of a super-rotating equatorial flow. The balance between the horizontal eddies and vertical eddies in the polar region is discussed and shown to produce an indirect overturning circulation above the jet. The indirect overturning may be related to the observed region of the polar dipole in the Venus atmosphere. Reservoirs of energy and momentum are calculated for each dynamical core and explicit sources and sinks are diagnosed from the general circulation model (GCM). The effect of a strong “sponge layer” damping to rest is compared with eddy damping and found to change significantly the momentum balance within the top “sponge layer” but does not significantly affect the super-rotation of the bulk of the atmosphere. The Lorenz (1955) energy cycle is calculated and the circulation is shown to be dominated by energy conversion between the mean potential energy and mean kinetic energy reservoirs, with barotropic energy conversion between the mean kinetic energy and eddy kinetic energy reservoirs. We suggest modifications to the GCM parameterizations on the basis of our analysis of the atmospheric circulation and discuss the effect of numerical parameterizations on the simulated atmosphere. |
| Title: | Mars Climate Sounder limb profile retrieval of atmospheric temperature, pressure, and dust and water ice opacity |
| Authors: | Kleinböhl, Armin; Schofield, John T.; Kass, David M.; Abdou, Wedad A.; Backus, Charles R.; Sen, Bhaswar; Shirley, James H.; Lawson, W. Gregory; Richardson, Mark I.; Taylor, Fredric W.; Teanby, Nicholas A.; McCleese, Daniel J. |
| Affiliation: | AA(Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California, USA); AB(Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California, USA); AC(Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California, USA); AD(Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California, USA); AE(Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California, USA); AF(Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California, USA); AG(Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California, USA); AH(Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, California, USA); AI(Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, California, USA); AJ(Clarendon Laboratory, Atmospheric, Oceanic, and Planetary Physics, University of Oxford, Oxford, UK); AK(Clarendon Laboratory, Atmospheric, Oceanic, and Planetary Physics, University of Oxford, Oxford, UK); AL(Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California, USA) |
| Journal: | Journal of Geophysical Research, Volume 114, Issue E10, CiteID E10006 |
| Publication Date: | Oct 2009 |
| Origin: | AGU |
| Keywords: | Planetary Sciences: Solid Surface Planets: Atmospheres (0343, 1060), Planetary Sciences: Solid Surface Planets: Remote sensing, Planetary Sciences: Solid Surface Planets: Instruments and techniques, Atmospheric Composition and Structure: Planetary atmospheres (5210, 5405, 5704) |
| DOI: | http://dx.doi.org/10.1029/2009JE003358 |
| Bibliographic Code: | 2009JGRE..11410006K |
| Abstract: | The Mars Climate Sounder (MCS) onboard the Mars Reconnaissance Orbiter is the latest of a series of investigations devoted to improving the understanding of current Martian climate. MCS is a nine-channel passive midinfrared and far-infrared filter radiometer designed to measure thermal emission in limb and on-planet geometries from which vertical profiles of atmospheric temperature, water vapor, dust, and condensates can be retrieved. Here we describe the algorithm that is used to retrieve atmospheric profiles from MCS limb measurements for delivery to the Planetary Data System. The algorithm is based on a modified Chahine method and uses a fast radiative transfer scheme based on the Curtis-Godson approximation. It retrieves pressure and vertical profiles of atmospheric temperature, dust opacity, and water ice opacity. Water vapor retrievals involve a different approach and will be reported separately. Pressure can be retrieved to a precision of 1-2% and is used to establish the vertical coordinate. Temperature profiles are retrieved over a range from 5-10 to 80-90 km altitude with a typical altitude resolution of 4-6 km and a precision between 0.5 and 2 K over most of this altitude range. Dust and water ice opacity profiles also achieve vertical resolutions of about 5 km and typically have precisions of 10‑4-10‑5 km‑1 at 463 cm‑1 and 843 cm‑1, respectively. Examples of temperature profiles as well as dust and water ice opacity profiles from the first year of the MCS mission are presented, and atmospheric features observed during periods employing different MCS operational modes are described. An intercomparison with historical temperature measurements from the Mars Global Surveyor mission shows good agreement. |
| Title: | Fitting the Viking lander surface pressure cycle with a Mars General Circulation Model |
| Authors: | Guo, Xin; Lawson, W. Gregory; Richardson, Mark I.; Toigo, Anthony |
| Affiliation: | AA(Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, California, USA); AB(Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, California, USA); AC(Ashima Research, Pasadena, California, USA); AD(Center for Radiophysics and Space Research, Cornell University, Ithaca, New York, USA) |
| Journal: | Journal of Geophysical Research, Volume 114, Issue E7, CiteID E07006 |
| Publication Date: | Jul 2009 |
| Origin: | AGU |
| Keywords: | Atmospheric Composition and Structure: Planetary atmospheres (5210, 5405, 5704), Planetary Sciences: Solar System Objects: Mars, Planetary Sciences: Solid Surface Planets: Polar regions, Planetary Sciences: Solid Surface Planets: Atmospheres (0343, 1060), Planetary Sciences: Solid Surface Planets: Ices |
| DOI: | http://dx.doi.org/10.1029/2008JE003302 |
| Bibliographic Code: | 2009JGRE..11407006G |
| Abstract: | We present a systematic attempt to fit the Viking lander surface pressure cycle using a Mars General Circulation Model, MarsWRF. Following the earlier study by Wood and Paige (1992) using a one-dimensional model, high-precision fitting was achieved by tuning five time-independent parameters: the albedo and emissivity of the seasonal caps of the two hemispheres and the total CO2 inventory in the atmosphere frost system. We used a linear iterative method to derive the best fit parameters: albedo of the northern cap = 0.795, emissivity of the northern cap = 0.485, albedo of the southern cap = 0.461, emissivity of the southern cap = 0.785, and total CO2 mass = 2.83 × 1016 kg. If these parameters are used in MarsWRF, the smoothed surface pressure residual at the VL1 site is always smaller than several Pascal through a year. As in other similar studies, the best fit parameters do not match well with the current estimation of the seasonal cap radiative properties, suggesting that important physics contributing to the energy balance not explicitly included in MarsWRF have been effectively aliased into the derived parameters. One such effect is likely the variation of thermal conductivity with depth in the regolith due to the presence of water ice. Including such a parameterization in the fitting process improves the reasonableness of the best fit cap properties, mostly improving the emissivities. The conductivities required in the north to provide the best fit are higher than those required in the south. A completely physically reasonable set of fit parameters could still not be attained. Like all prior published GCM simulations, none of the cases considered are capable of predicting a residual southern CO2 cap. |
| Title: | Thermal tides in the Martian middle atmosphere as seen by the Mars Climate Sounder |
| Authors: | Lee, C.; Lawson, W. G.; Richardson, M. I.; Heavens, N. G.; Kleinböhl, A.; Banfield, D.; McCleese, D. J.; Zurek, R.; Kass, D.; Schofield, J. T.; Leovy, C. B.; Taylor, F. W.; Toigo, A. D. |
| Affiliation: | AA(Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, California, USA); AB(Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, California, USA); AC(Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, California, USA); AD(Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, California, USA); AE(Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California, USA); AF(Department of Astronomy, Cornell University, Ithaca, New York, USA); AG(Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California, USA); AH(Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California, USA); AI(Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California, USA); AJ(Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California, USA); AK(Department of Atmospheric Sciences, University of Washington, Seattle, Washington, USA); AL(Department of Physics, University of Oxford, Oxford, UK); AM(Department of Astronomy, Cornell University, Ithaca, New York, USA) |
| Journal: | Journal of Geophysical Research, Volume 114, Issue E3, CiteID E03005 |
| Publication Date: | Mar 2009 |
| Origin: | AGU |
| Keywords: | Atmospheric Processes: Tides and planetary waves, Planetary Sciences: Solar System Objects: Mars, Atmospheric Processes: General circulation (1223), Atmospheric Processes: Middle atmosphere dynamics (0341, 0342), Atmospheric Processes: Remote sensing |
| DOI: | http://dx.doi.org/10.1029/2008JE003285 |
| Bibliographic Code: | 2009JGRE..11403005L |
| Abstract: | The first systematic observations of the middle atmosphere of Mars (35-80km) with the Mars Climate Sounder (MCS) show dramatic patterns of diurnal thermal variation, evident in retrievals of temperature and water ice opacity. At the time of writing, the data set of MCS limb retrievals is sufficient for spectral analysis within a limited range of latitudes and seasons. This analysis shows that these thermal variations are almost exclusively associated with a diurnal thermal tide. Using a Martian general circulation model to extend our analysis, we show that the diurnal thermal tide dominates these patterns for all latitudes and all seasons. |
| Title: | Intense polar temperature inversion in the middle atmosphere on Mars |
| Authors: | McCleese, D. J.; Schofield, J. T.; Taylor, F. W.; Abdou, W. A.; Aharonson, O.; Banfield, D.; Calcutt, S. B.; Heavens, N. G.; Irwin, P. G. J.; Kass, D. M.; Kleinböhl, A.; Lawson, W. G.; Leovy, C. B.; Lewis, S. R.; Paige, D. A.; Read, P. L.; Richardson, M. I.; Teanby, N.; Zurek, R. W. |
| Affiliation: | AA(Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California 91103, USA), AB(Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California 91103, USA), AC(Department of Physics, University of Oxford, Clarendon Laboratory, Oxford OX1 3PU, UK), AD(Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California 91103, USA), AE(Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, California 91105, USA), AF(Department of Astronomy, Cornell University, Ithaca, New York 14850, USA), AG(Department of Physics, University of Oxford, Clarendon Laboratory, Oxford OX1 3PU, UK), AH(Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, California 91105, USA), AI(Department of Physics, University of Oxford, Clarendon Laboratory, Oxford OX1 3PU, UK), AJ(Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California 91103, USA), AK(Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California 91103, USA), AL(Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, California 91105, USA), AM(Department of Atmospheric Sciences, University of Washington, Seattle, Washington 98101, USA), AN(Department of Physics and Astronomy, Open University, Milton Keynes MK7 6AA, UK), AO(Department of Earth and Space Sciences, University of California, Los Angeles, California 90024, USA), AP(Department of Physics, University of Oxford, Clarendon Laboratory, Oxford OX1 3PU, UK), AQ(Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, California 91105, USA), AR(Department of Physics, University of Oxford, Clarendon Laboratory, Oxford OX1 3PU, UK), AS(Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California 91103, USA) |
| Journal: | Nature Geoscience, Volume 1, Issue 11, pp. 745-749 (2008). |
| Publication Date: | Nov 2008 |
| Origin: | NATURE |
| DOI: | http://dx.doi.org/10.1038/ngeo332 |
| Bibliographic Code: | 2008NatGe…1..745M |
| Abstract: | Current understanding of weather, climate and global atmospheric circulation on Mars is incomplete, in particular at altitudes above about 30km. General circulation models for Mars are similar to those developed for weather and climate forecasting on Earth and require more martian observations to allow testing and model improvements. However, the available measurements of martian atmospheric temperatures, winds, water vapour and airborne dust are generally restricted to the region close to the surface and lack the vertical resolution and global coverage that is necessary to shed light on the dynamics of Mars’ middle atmosphere at altitudes between 30 and 80km (ref. 7). Here we report high-resolution observations from the Mars Climate Sounder instrument on the Mars Reconnaissance Orbiter. These observations show an intense warming of the middle atmosphere over the south polar region in winter that is at least 10-20K warmer than predicted by current model simulations. To explain this finding, we suggest that the atmospheric downwelling circulation over the pole, which is part of the equator-to-pole Hadley circulation, may be as much as 50% more vigorous than expected, with consequences for the cycles of water, dust and CO2 that regulate the present-day climate on Mars. |
| Title: | Two aerodynamic roughness maps derived from Mars Orbiter Laser Altimeter (MOLA) data and their effects on boundary layer properties in a Mars general circulation model (GCM) |
| Authors: | Heavens, N. G.; Richardson, M. I.; Toigo, A. D. |
| Affiliation: | AA(Division of the Geological and Planetary Sciences, California Institute of Technology, Pasadena, California, USA); AB(Division of the Geological and Planetary Sciences, California Institute of Technology, Pasadena, California, USA); AC(Center for Radiophysics and Space Research, Cornell University, Ithaca, New York, USA) |
| Journal: | Journal of Geophysical Research, Volume 113, Issue E2, CiteID E02014 |
| Publication Date: | Feb 2008 |
| Origin: | AGU |
| Keywords: | Planetary Sciences: Solar System Objects: Mars, Planetary Sciences: Solid Surface Planets: Atmospheres (0343, 1060), Planetary Sciences: Solid Surface Planets: Surface materials and properties, Atmospheric Processes: Boundary layer processes, Atmospheric Processes: Global climate models (1626, 4928) |
| Abstract Copyright: | (c) 2008: American Geophysical Union |
| DOI: | http://dx.doi.org/10.1029/2007JE002991 |
| Bibliographic Code: | 2008JGRE..11302014H |
| Abstract: | Mechanical (forced convective) and free convective turbulent heat and momentum transfer in the lower atmosphere of a terrestrial planet has some dependence on the roughness characteristics of the surface, often quantified in terms of a single roughness parameter which is then used to calculate the coefficients that govern heat and momentum transport between the surface and the boundary layer. We take two different approaches for deriving this aerodynamic roughness parameter for Martian surfaces using data from the Mars Orbiter Laser Altimeter. We then use these two different roughness maps to force the boundary layer in a Mars general circulation model, primarily investigating differences in temperatures and the pressure cycle between the two simulations. While the pressure cycle does not vary significantly, spring and summer high-latitude temperatures are somewhat sensitive to the input roughness conditions. Daytime temperatures may vary up to 10 K seasonally, though zonally and annually averaged daytime temperatures vary only by ~1 K. Our results can be explained by the dominance of mechanical over convective turbulent heat transfer processes on Mars. These simulations, however, use a prescribed atmospheric dust distribution and thus only provide a minimum estimate of the uncertainty in boundary layer temperatures because of this plausible range of aerodynamic roughness parameters. Since surface roughness determines the threshold wind velocity for dust lifting we anticipate a much larger effect of the aerodynamic roughness parameter on temperatures when the dust distribution is allowed to vary according to predicted lifting and transport. |
| Title: | Dust haze in Valles Marineris observed by HRSC and OMEGA on board Mars Express |
| Authors: | Inada, A.; Garcia-Comas, M.; Altieri, F.; Gwinner, K.; Poulet, F.; Bellucci, G.; Keller, H. U.; Markiewicz, W. J.; Richardson, M. I.; Hoekzema, N.; Neukum, G.; Bibring, J.-P. |
| Affiliation: | AA(Geological and Planetary Sciences, California Institute of Technology, Pasadena, California, USA); AB(Max-Plank-Institute of Solar System Research, Lindau, Germany); AC(Istituto di Fisica dello Spazio Interplanetario, INAF, Rome, Italy); AD(Institute of Planetary Research, German Aerospace Center (DLR), Berlin, Germany); AE(IAU, Université Paris, Orsay, France); AF(Istituto di Fisica dello Spazio Interplanetario, INAF, Rome, Italy); AG(Max-Plank-Institute of Solar System Research, Lindau, Germany); AH(Max-Plank-Institute of Solar System Research, Lindau, Germany); AI(Geological and Planetary Sciences, California Institute of Technology, Pasadena, California, USA); AJ(Max-Plank-Institute of Solar System Research, Lindau, Germany); AK(Institute of Geological Sciences, Freie Universität Berlin, Berlin, Germany); AL(IAU, Université Paris, Orsay, France) |
| Journal: | Journal of Geophysical Research, Volume 113, Issue E2, CiteID E02004 |
| Publication Date: | Feb 2008 |
| Origin: | AGU |
| Keywords: | Planetary Sciences: Solar System Objects: Mars, Planetary Sciences: Solid Surface Planets: Atmospheres (0343, 1060), Planetary Sciences: Solid Surface Planets: Aurorae and airglow, Planetary Sciences: Solid Surface Planets: Remote sensing |
| Abstract Copyright: | (c) 2008: American Geophysical Union |
| DOI: | http://dx.doi.org/10.1029/2007JE002893 |
| Bibliographic Code: | 2008JGRE..11302004I |
| Abstract: | We present analysis of a bright haze observed inside Valles Marineris, which formed in mid northern spring. The data were collected by the High Resolution Stereo Camera (HRSC) and the imaging spectrometer, Observatoire pour la Minéralogie, l’Eau, les Glaces et l’Activité (OMEGA), aboard Mars Express. This study provides a case example of the power of simultaneous multiple emission angle and hyperspectral imaging for study of aerosols and clouds in the Martian atmosphere. The haze appeared thinner after three days and disappeared in nine days. It was limited to a 2-km layer at the bottom of the canyon. The color was redder than the underlying surface. The analysis of the OMEGA spectra indicates that this haze was composed of dust particles. The dust layer appeared brighter with the HRSC stereo channels than the nadir channel due to longer scattering paths. We have estimated the optical depth of the haze by fitting both HRSC and OMEGA data with radiative transfer calculations. The retrieval of the optical depth is very sensitive to the aerosol scattering model used and the reflectance of the surface. Applying an aerosol scattering model derived from sky surveys at a constant elevation by the Imager for Mars Pathfinder, the optical depth of the haze is estimated from HRSC data to be within 1.7 to 2.3 at the wavelength (λ) of 0.675 μm. The wavelength dependence is obtained from OMEGA spectrum. It increases to 2.2-2.6 at λ = 1.35 μm and moderately decreases to 1.2-1.8 at λ = 2.4 μm. |
| Title: | High-resolution atmospheric observations by the Mars Odyssey Thermal Emission Imaging System |
| Authors: | Inada, Ai; Richardson, Mark I.; McConnochie, Timothy H.; Strausberg, Melissa J.; Wang, Huiqun; Bell, James F. |
| Affiliation: | AA(California Institute of Technology, M.S. 150-21, 1200 E. California Blvd., Pasadena, CA 91125, USA), AB(California Institute of Technology, M.S. 150-21, 1200 E. California Blvd., Pasadena, CA 91125, USA), AC(NASA Goddard Space Flight Center, Greenbelt, MD 20771, USA), AD(University of California, Los Angeles, 7229 Math Science Bld., Los Angeles, CA 90095-1565, USA), AE(Harvard-Smithsonian Center for Astrophysics, MS-50, 60 Garden Street, Cambridge, MA 02138, USA), AF(Cornell University, Space Sciences Building, Cornell University, Ithaca, NY 14853, USA) |
| Journal: | Icarus, Volume 192, Issue 2, p. 378-395. |
| Publication Date: | Dec 2007 |
| Origin: | ELSEVIER |
| Abstract Copyright: | Elsevier Inc. |
| DOI: | http://dx.doi.org/10.1016/j.icarus.2007.07.020 |
| Bibliographic Code: | 2007Icar..192..378I |
| Abstract: | High-resolution observations of atmospheric phenomena by the Mars Odyssey Thermal Emission Imaging System (THEMIS) during its first mapping year are presented. An atmospheric campaign was implemented on the basis of previous spacecraft imaging. This campaign, however, proved of limited success. This appears to be due to the late local time of the Odyssey orbit (the locations of activity at 4 6 p.m. appear to be different from those at 2 p.m.). Ironically, images targeting the surface were more useful for study of the atmosphere than those images specifically targeting atmospheric features. While many previously recognized features were found, novel THEMIS observations included persistent clouds in the southern polar layered deposits, dust or condensate plumes on the northern polar layered deposits, dust plumes as constituent parts of local dust storms, and mesospheric clouds. The former two features tend to be aligned parallel and normal to polar troughs, respectively, suggesting a wind system directed normal to troughs and radially outward from the center of the polar deposits. This is consistent with katabatic drainage of air off the polar deposits, analogous to flow off Antarctica. The observation of dust lifting plumes at unprecedented resolution associated with local dust storms not only demonstrates the importance of mean wind stresses (as opposed to dust devils) in initiation of dust storms, but is also seen to be morphologically identical to dust lifting in terrestrial dust storms. As Odyssey moves to earlier local times, we suggest that the atmospheric campaign from the first mapping year be repeated. |
| Title: | PlanetWRF: A General Purpose, Local to Global Numerical Model for Planetary Atmospheric and Climate Dynamics |
| Authors: | Richardson, M. I.; Toigo, A. D; Newman, C. E. |
| Journal: | Journal of Geophysical Research, Volume 112, Issue E9, CiteID E09001 |
| Publication Date: | Sep 2007 |
| DOI: | http://dx.doi.org/10.1029/2006JE002825 |
| Abstract: | A new planetary atmospheric numerical model, “planetWRF,” has been developed by modifying the Weather Research and Forecasting (WRF) model. The model has generalized map projection, multiscale, and nesting capabilities, blurring the distinction between global and mesoscale models and enabling investigation of coupling between processes on all scales, including global. The model can also be run in one, two, or three dimensions. The conversion of the dynamical core for global application by altering the map projection grid and the boundary conditions as well as conversion of the physics parameterizations and constants for planetary application are described. Validation of the global dynamical core through use of standard forcing scenarios is presented. Example results from a series of simulations for Mars, Titan, and Venus are shown to demonstrate that the model performs well for a variety of planets and operating modes (microscale, mesoscale, and global scale). |
| Title: | Surface dust redistribution on Mars as observed by the Mars Global Surveyor and Viking orbiters |
| Authors: | Szwast, Mark A.; Richardson, Mark I.; Vasavada, Ashwin R. |
| Affiliation: | AA(Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, California, USA); AB(Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, California, USA); AC(Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California, USA) |
| Journal: | Journal of Geophysical Research, Volume 111, Issue E11, CiteID E11008 |
| Publication Date: | Nov 2006 |
| Origin: | AGU |
| Keywords: | Planetary Sciences: Solar System Objects: Mars, Planetary Sciences: Solid Surface Planets: Atmospheres (0343, 1060), Planetary Sciences: Solid Surface Planets: Meteorology (3346), Planetary Sciences: Solid Surface Planets: Remote sensing, Atmospheric Composition and Structure: Aerosols and particles (0345, 4801, 4906) |
| Abstract Copyright: | (c) 2006: American Geophysical Union |
| DOI: | http://dx.doi.org/10.1029/2005JE002485 |
| Bibliographic Code: | 2006JGRE..11111008S |
| Abstract: | The variation of surface dust coverage on Mars is mapped using Mars Global Surveyor (MGS) and Viking albedo data. Albedo is shown to correlate well with spectrally derived measurements of surface dust abundance and is subsequently used to gauge dust coverage. Atmospheric aerosols modify the albedo observed from orbit, complicating this analysis. However, opacity cycles are highly repeatable, and simultaneous, independent records of aerosol opacities are available to isolate their impact. The MGS albedo and imaging data contain global coverage on a daily basis, allowing the relationship between dust cover and specific meteorological events to be elucidated. The 2001 global dust storm produced the largest changes in surface dust coverage during the MGS mission. Other processes yielding significant changes include seasonal cap-edge winds, seasonally varying regional winds, local/regional dust storms, and extratropical cyclones. Dust devils and ongoing, small-scale dust lifting do not appear to significantly modify the global patterns of dust cover. Finally, we show that the apparent long-term darkening of the southern mid and high latitudes between the Viking and MGS eras is largely a consequence of the timing of image acquisition relative to global dust storms and surface dust “cleaning” by the seasonal ice cap; it does not represent a steady decadal-scale, secular change. In fact, following the 2001 global dust storm, in late southern spring, the southern hemisphere was brighter in MGS than in Viking data. This study reveals albedo to be a dynamic, climatological variable for Mars, similar to sea-surface temperature for terrestrial meteorology and climate. |
| Title: | Simulation of spontaneous and variable global dust storms with the GFDL Mars GCM |
| Authors: | Basu, Shabari; Wilson, John; Richardson, Mark; Ingersoll, Andrew |
| Affiliation: | AA(Department of Atmospheric Science, Texas A&M University, College Station, Texas, USA); AB(Geophysical Fluid Dynamics Laboratory, National Oceanic and Atmospheric Administration, Princeton, New Jersey, USA); AC(Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, California, USA); AD(Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, California, USA) |
| Journal: | Journal of Geophysical Research, Volume 111, Issue E9, CiteID E09004 |
| Publication Date: | Sep 2006 |
| Origin: | AGU |
| Keywords: | Atmospheric Composition and Structure: Planetary atmospheres (5210, 5405, 5704), Global Change: Atmosphere (0315, 0325), Global Change: Climate dynamics (0429, 3309), Global Change: Global climate models (3337, 4928), Global Change: Land/atmosphere interactions (1218, 1843, 3322) |
| Abstract Copyright: | (c) 2006: American Geophysical Union |
| DOI: | http://dx.doi.org/10.1029/2005JE002660 |
| Bibliographic Code: | 2006JGRE..11109004B |
| Abstract: | We report on the successful simulation of global dust storms in a general circulation model. The simulated storms develop spontaneously in multiyear simulations and exhibit significant interannual variability. The simulated storms produce dramatic increases in atmospheric dustiness, global-mean air temperatures, and atmospheric circulation intensity, in accord with observations. As with observed global storms, spontaneous initiation of storms in the model occurs in southern spring and summer, and there is significant interannual variability in storm development: years with no storms are interspersed with years with storms of various sizes and specific seasonal date of initiation. Our results support the idea that variable and spontaneous global dust storm behavior can emerge from a periodically forced system (the only forcing being the diurnal and seasonal cycles) when the dust injection mechanism involves an activation threshold. In our simulations, surface wind stresses associated with resolved, large-scale (>300 km) wind systems initiate the storms. These winds are generally associated with the seasonally migrating CO2 cap boundary and sloping topography of the Hellas basin, thermal tides, and traveling waves. A very limited number of large storms begin with lifting along the frontal zones associated with traveling waves in the northern hemisphere. Explosive growth to global scales results from the intensification of the Hadley circulation and the activation of secondary dust-lifting centers. |
| Title: | Relationship between frontal dust storms and transient eddy activity in the northern hemisphere of Mars as observed by Mars Global Surveyor |
| Authors: | Wang, Huiqun; Zurek, Richard W.; Richardson, Mark I. |
| Affiliation: | AA(Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, California, USA); AB(Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California, USA); AC(Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, California, USA) |
| Journal: | Journal of Geophysical Research, Volume 110, Issue E7, CiteID E07005 |
| Publication Date: | Jul 2005 |
| Origin: | AGU |
| Keywords: | Planetary Sciences: Solid Surface Planets: Atmospheres (0343, 1060), Planetary Sciences: Solar System Objects: Mars |
| Abstract Copyright: | (c) 2005: American Geophysical Union |
| DOI: | http://dx.doi.org/10.1029/2005JE002423 |
| Bibliographic Code: | 2005JGRE..11007005W |
| Abstract: | We have compiled a catalog of frontal dust storms in the northern hemisphere using Mars Orbiter Camera daily global maps spanning ~2.3 Martian years of Mars Global Surveyor (MGS) observations (from 1999 to 2003). The most vigorous frontal storms that flush dust to the low latitudes occur in early-mid fall and mid-late winter, away from the northern winter solstice. While many streaks are observed in the polar hood during the winter solstice period, no frontal dust storms are observed in the vicinity of the north polar region. We have also analyzed simultaneous MGS Thermal Emission Spectrometer (TES) temperature data and found statistically significant negative temperature anomalies associated with frontal storms. In the lowest scale height of the atmosphere, the geographical and seasonal distributions of temperature standard deviations associated with transient variations agree well with the distributions of frontal storms. The correlation deteriorates with increasing altitude, suggesting that lower-level temperature waves are associated with the frontal dust storms. Specifically, eastward traveling m = 3 waves with periods of 2-3 sols appear to be closely related to the development of flushing frontal storms. |
| Title: | Aeolian processes in Proctor Crater on Mars: Mesoscale modeling of dune-forming winds |
| Authors: | Fenton, Lori K.; Toigo, Anthony D.; Richardson, Mark I. |
| Affiliation: | AA(Department of Geology, Arizona State University, Tempe, Arizona, USA); AB(Graduate School of Science and Technology, Kobe University, Kobe, Japan); AC(Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, California, USA) |
| Journal: | Journal of Geophysical Research, Volume 110, Issue E6, CiteID E06005 |
| Publication Date: | Jun 2005 |
| Origin: | AGU |
| Keywords: | Atmospheric Processes: Planetary meteorology (5445, 5739), Atmospheric Processes: Boundary layer processes, Atmospheric Processes: Climatology (1616, 1620, 3305, 4215, 8408), Planetary Sciences: Solid Surface Planets: Erosion and weathering, Global Change: Geomorphology and weathering (0790, 1824, 1825, 1826, 1886) |
| Abstract Copyright: | (c) 2005: American Geophysical Union |
| DOI: | http://dx.doi.org/10.1029/2004JE002309 |
| Bibliographic Code: | 2005JGRE..11006005F |
| Abstract: | Both atmospheric modeling and spacecraft imagery of Mars are now of sufficient quality that the two can be used in conjunction to acquire an understanding of regional- and local-scale aeolian processes on Mars. We apply a mesoscale atmospheric model adapted for use on Mars (the Mars MM5) to Proctor Crater, a 150 km diameter crater in the southern highlands. Proctor Crater contains numerous aeolian features that indicate wind direction, including a large dark dune field with reversing transverse and star dunes containing three different slipface orientations, small and older bright bedforms that are most likely transverse granule ripples, and seasonally erased dust devil tracks. Results from model runs spanning a Martian year, with a horizontal grid spacing of 10 km, predict winds aligned with two of the three dune slipfaces as well as spring and summer winds matching the dust devil track orientations. The primary (most prevalent) dune slipface orientation corresponds to a fall and winter westerly wind created by geostrophic forces. The tertiary dune slipface orientation is caused by spring and summer evening katabatic flows down the eastern rim of the crater, influencing only the eastern portion of the crater floor. The dunes are trapped in the crater because the tertiary winds, enhanced by topography, counter transport from the oppositely oriented primary winds, which may have originally carried sand into the crater. The dust devil tracks are caused by light spring and summer westerly winds during the early afternoon caused by planetary rotation. The secondary dune slipface orientation is not predicted by model results from either the Mars MM5 or the Geophysical Fluid Dynamics Laboratory Mars general circulation model. The reason for this is not clear, and the wind circulation pattern that creates this dune slipface is not well constrained. The Mars MM5 model runs do not predict stresses above the saltation threshold for dune sand of the appropriate size and composition. As with previous work, the calculated wind velocities are too low, which may be caused by too large of a grid spacing. |
| Title: | A survey of Martian dust devil activity using Mars Global Surveyor Mars Orbiter Camera images |
| Authors: | Fisher, Jenny A.; Richardson, Mark I.; Newman, Claire E.; Szwast, Mark A.; Graf, Chelsea; Basu, Shabari; Ewald, Shawn P.; Toigo, Anthony D.; Wilson, R. John |
| Affiliation: | AA(Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, California, USA); AB(Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, California, USA); AC(Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, California, USA); AD(Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, California, USA); AE(La Canada High School, La Canada, California, USA); AF(Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, California, USA); AG(Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, California, USA); AH(Department of Astronomy, Cornell University, Ithaca, New York, USA); AI(Geophysical Fluid Dynamics Laboratory, Princeton, New Jersey, USA) |
| Journal: | Journal of Geophysical Research, Volume 110, Issue E3, CiteID E03004 |
| Publication Date: | Mar 2005 |
| Origin: | AGU |
| Keywords: | Atmospheric Processes: Convective processes, Planetary Sciences: Solid Surface Planets: Atmospheres (0343, 1060), Planetary Sciences: Solid Surface Planets: Meteorology (3346), Planetary Sciences: Solar System Objects: Dust, Planetary Sciences: Solar System Objects: Mars |
| Abstract Copyright: | (c) 2005: American Geophysical Union |
| DOI: | http://dx.doi.org/10.1029/2003JE002165 |
| Bibliographic Code: | 2005JGRE..11003004F |
| Abstract: | A survey of dust devils using the Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) wide- and narrow-angle (WA and NA) images has been undertaken. The survey comprises two parts: (1) sampling of nine broad regions from September 1997 to July 2001 and (2) a focused seasonal monitoring of variability in the Amazonis region, an active dust devil site, from March 2001 to April 2004. For part 1, dust devils were identified in NA and WA images, and dust devil tracks were identified in NA images. Great spatial variability in dust devil occurrence is highlighted, with Amazonis Planitia being the most active region examined. Other active regions included Cimmerium, Sinai, and Solis. Numerous dust devil tracks, but very few dust devils, were observed in Casius. This may suggest dust devils here occur at local times other than that of the MGS orbit (~2 pm). Alternatively, variations in surface properties may affect the ability of dust devils to leave visible tracks. The seasonal campaign within Amazonis shows a relatively smooth variation of dust devil activity with season, peaking in mid northern summer and falling to zero in southern spring and summer. This pattern of activity correlates well with the boundary layer maximum depth and hence the vigor of convection. Global maps of boundary layer depth and surface temperature do not predict that Amazonis should be especially active, potentially suggesting a role for mesoscale circulations. Measurement of observed dust devils yields heights of up to 8 km and widths in excess of 0.5 km. |
| Title: | Long-term evolution of transient liquid water on Mars |
| Authors: | Richardson, Mark I.; Mischna, Michael A. |
| Affiliation: | AA(Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, California, USA); AB(Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California, USA) |
| Journal: | Journal of Geophysical Research, Volume 110, Issue E3, CiteID E03003 |
| Publication Date: | Mar 2005 |
| Origin: | AGU |
| Keywords: | Planetary Sciences: Solar System Objects: Mars, Planetary Sciences: Solid Surface Planets: Erosion and weathering, Planetary Sciences: Solid Surface Planets: Atmospheres (0343, 1060), Atmospheric Composition and Structure: Planetary atmospheres (5210, 5405, 5704), Atmospheric Processes: Paleoclimatology (0473, 4900) |
| Abstract Copyright: | (c) 2005: American Geophysical Union |
| DOI: | http://dx.doi.org/10.1029/2004JE002367 |
| Bibliographic Code: | 2005JGRE..11003003R |
| Abstract: | Liquid water is not currently stable on the surface of Mars; however, transient liquid water (ice melt) may occur if the surface temperature is between the melting and boiling points. Such conditions are met on Mars with current surface pressures and obliquity due to the large diurnal range of surface temperatures. This yields the potential for transient, nonequilibrium liquid water. A general circulation model is used to undertake an initial exploration of the variation of this “transient liquid water potential” (TLWP) for different obliquities and over a range of increased pressures representing progressively earlier phases of Martian geological history. At higher obliquities and slightly higher surface pressures (<50 mbar), TLWP conditions are met over a very large fraction of the planet. As the surface pressure is increased above about 50-100 mbar, however, increased atmospheric thermal blanketing reduces the diurnal surface temperature range, essentially eliminating the possibility of even transient liquid water. At high enough pressures, the mean temperature is sufficiently elevated to allow stable liquid water. Thus the potential for liquid water on Mars has not decreased monotonically over planetary history as the atmosphere was lost. Instead, a distinct minimum in TLWP (the “dead zone”) will have occurred during the extended period for which pressures were in the middle range between about 0.1 and 1 bar. This has direct and restrictive implications for chemical weathering and life. The fundamental conclusion of this study is largely insensitive to invocation of brines and to more detailed treatment of atmospheric radiative processes. |
| Title: | Observations of the initiation and evolution of the 2001 Mars global dust storm |
| Authors: | Strausberg, Melissa J.; Wang, Huiqun; Richardson, Mark I.; Ewald, Shawn P.; Toigo, Anthony D. |
| Affiliation: | AA(Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, California, USA); AB(Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, California, USA); AC(Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, California, USA); AD(Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, California, USA); AE(Center for Radiophysics and Space Research, Cornell University, Ithaca, New York, USA) |
| Journal: | Journal of Geophysical Research, Volume 110, Issue E2, CiteID E02006 |
| Publication Date: | Feb 2005 |
| Origin: | AGU |
| Keywords: | Planetary Sciences: Solar System Objects: Mars, Planetary Sciences: Solid Surface Planets: Meteorology (3346), Planetary Sciences: Solid Surface Planets: Remote sensing, Planetary Sciences: Solid Surface Planets: Atmospheres (0343, 1060) |
| Abstract Copyright: | (c) 2005: American Geophysical Union |
| DOI: | http://dx.doi.org/10.1029/2004JE002361 |
| Bibliographic Code: | 2005JGRE..11002006S |
| Abstract: | A global dust storm occurred on Mars between June and October 2001. The storm began near Hellas just before southern spring equinox (~Ls = 177°). Local storms, likely forced by a combination of slope-flow and ice cap thermal contrasts, were observed to propagate along the northwestern rim of Hellas, apparently triggering the global storm. Cap-edge storm activity for much of late southern winter was similar in 2001 to one Mars year earlier; however, a very large storm propagated into the basin just after Ls = 177°. Subsequently, the total area of storm activity in 2001 was roughly double that of the previous year. For about 10 days, dust lifting was limited to the Hellas region. As additional storms propagated into Hellas, activity built and extended northward into Syrtis and eastward into Hesperia. It is not clear whether transport or spreading of lifting were of greatest importance for expansion. At Ls = 185° the storm began to spread rapidly to the east, along a line from the southern pole to the northern tropics. Essentially no storm propagation to the west occurred, yielding strong zonal asymmetry of expansion. As the dust storm reached the western edge of Tharsis, secondary dust lifting centers developed in Daedalia and Solis (southeastern Tharsis). Subsequently, the storm rapidly encompassed the planet (by Ls = 193°). Once fully global, the Syria/Solis/Daedalia lifting center appeared to dominate (on the basis of cloud top morphology), with Hellas quiescent. By Ls = 212°, lifting could no longer be discerned. Thereafter, dust haze appeared uniform and diffuse, and decay appeared to have set in. |
| Title: | A reanalysis of water abundances in the Martian atmosphere at high obliquity |
| Authors: | Mischna, Michael A.; Richardson, Mark I. |
| Affiliation: | AA(Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California, USA); AB(Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, California, USA) |
| Journal: | Geophysical Research Letters, Volume 32, Issue 3, CiteID L03201 |
| Publication Date: | Feb 2005 |
| Origin: | AGU |
| Keywords: | Planetary Sciences: Solid Surface Planets: Atmospheres (0343, 1060), Planetary Sciences: Solar System Objects: Mars, Atmospheric Composition and Structure: Planetary atmospheres (5210, 5405, 5704), Atmospheric Processes: Planetary meteorology (5445, 5739), Planetary Sciences: Solid Surface Planets: Polar regions |
| Abstract Copyright: | (c) 2005: American Geophysical Union |
| DOI: | http://dx.doi.org/10.1029/2004GL021865 |
| Bibliographic Code: | 2005GeoRL..3203201M |
| Abstract: | We take a new look at expected atmospheric water vapor abundances on Mars during periods of high obliquity using the Geophysical Fluid Dynamics Laboratory Mars General Circulation Model. For the first time, the sublimation and burial of the present-day residual polar caps beneath a sublimation lag is considered as the planet shifts from lower to high (45°) obliquity periods. Following the elimination of the polar deposits, the only sources for atmospheric water at high obliquity are the low latitude ice deposits emplaced prior to elimination of the polar source. Annual average water vapor abundances are predicted to be only ~20-80 prμm during extended periods of high obliquity, one to two orders of magnitude less than previous estimates. This has implications for the climate history of the planet as it suggests that during extended periods of high obliquity, there is not a significant greenhouse warming effect from elevated atmospheric water vapor. |
| Title: | Simulation of the Martian dust cycle with the GFDL Mars GCM |
| Authors: | Basu, Shabari; Richardson, Mark I.; Wilson, R. John |
| Affiliation: | AA(Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, California, USA); AB(Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, California, USA); AC(Geophysical Fluid Dynamics Laboratory, National Oceanic and Atmospheric Administration, Princeton, New Jersey, USA) |
| Journal: | Journal of Geophysical Research, Volume 109, Issue E11, CiteID E11006 |
| Publication Date: | Nov 2004 |
| Origin: | AGU |
| Keywords: | Planetology: Solar System Objects: Mars, Planetology: Solid Surface Planets: Meteorology (3346), Planetology: Solid Surface Planets: Atmospheres-structure and dynamics, Meteorology and Atmospheric Dynamics: General circulation, Atmospheric Composition and Structure: Aerosols and particles (0345, 4801) |
| Abstract Copyright: | (c) 2004: American Geophysical Union |
| DOI: | http://dx.doi.org/10.1029/2004JE002243 |
| Bibliographic Code: | 2004JGRE..10911006B |
| Abstract: | The Martian seasonal dust cycle is examined with a general circulation model (GCM) that treats dust as a radiatively and dynamically interactive trace species. Dust injection is parameterized as being due to convective processes (such as dust devils) and model-resolved wind stresses. Size-dependent dust settling, transport by large-scale winds and subgrid scale diffusion, and radiative heating due to the predicted dust distribution are treated. Multiyear Viking and Mars Global Surveyor air temperature data are used to quantitatively assess the simulations. Varying the three free parameters for the two dust injection schemes (rate parameters for the two schemes and a threshold for wind-stress lifting), we find that the highly repeatable northern spring and summer temperatures can be reproduced by the model if the background dust haze is supplied by either convective lifting or by stress lifting with a very low threshold and a low injection rate. Dust injection due to high-threshold, high-rate stress lifting must be added to these to generate spontaneous and variable dust storms. In order to supply the background haze, widespread and ongoing lifting is required by the model. Imaging data provide a viable candidate mechanism for convective lifting, in the form of dust devils. However, observed nonconvective lifting systems (local storms, etc.) appear insufficiently frequent and widespread to satisfy the role. On the basis of the model results and thermal and imaging data, we suggest that the background dust haze on Mars is maintained by convective processes, specifically, dust devils. Combining the convective scheme and high-threshold stress lifting, we obtain a “best fit” multiyear simulation, which produces a realistic thermal state in northern spring and summer and, for the first time, spontaneous and interannually variable global dust storms. |
| Title: | Meteorology of proposed Mars Exploration Rover landing sites |
| Authors: | Toigo, Anthony D.; Richardson, Mark I. |
| Journal: | Journal of Geophysical Research, Volume 108, Issue E12, pp. ROV 33-1, CiteID 8092, DOI 10.1029/2003JE002064 |
| Publication Date: | Nov 2003 |
| Origin: | AGU |
| Keywords: | Planetary Sciences: Meteorology (3346), Meteorology and Atmospheric Dynamics: Mesoscale meteorology, Meteorology and Atmospheric Dynamics: Numerical modeling and data assimilation, Meteorology and Atmospheric Dynamics: Boundary layer processes, Meteorology and Atmospheric Dynamics: Paleoclimatology |
| Abstract Copyright: | (c) 2003: American Geophysical Union |
| DOI: | http://dx.doi.org/10.1029/2003JE002064 |
| Bibliographic Code: | 2003JGRE..108.8092T |
| Abstract: | A descriptive study of the near-surface meteorology at three of the potential Mars Exploration Rover (MER) landing sites (Terra Meridiani, Gusev Crater, and Melas Chasma) is presented using global and mesoscale models. The mesoscale model provides a detailed picture of meteorology on scales down to a few kilometers but is not well constrained by observations away from the Viking and Pathfinder landing sites. As such, care must be taken in the interpretation of the results, with there being high confidence that the types of circulations predicted will indeed occur and somewhat less in the quantitative precision of the predictions and the local-time phasing of predicted circulations. All three landing sites are in the tropics and are affected by Hadley circulation, by diurnal variations due to the global thermal tide, and by planetary scale topography (in these particular cases from Tharsis, Elysium, and the global topographic dichotomy boundary). Terra Meridiani is least affected by large variations in local topography. Mean winds at Terra Meridiani during MER landing would be less than 10 m/s with little vertical shear. However, these low wind speeds result from strong mixing in the early afternoon convective boundary layer, which creates its own hazard in the horizontal variation of vertical winds of up to 8 m/s (both upward and downward). In Gusev Crater the topography of Ma’adim Vallis and the crater rim generates strong diurnally reversing channeling of wind in Ma’adim Vallis and diurnally reversing radial flow in the crater associated with thermal slope winds on the crater rim. The overturning circulation in Gusev Crater slightly suppresses the daytime convective boundary layer. Melas Chasma in Valles Marineris provides an example of strong topographic forcing of near-surface circulation. Of particular interest is the channeling of regional scale wind toward the center of the Tharsis plateau during the evening. This results in a surface level jet along the canyon of over 25 m/s. Drainage of air from the plateau and into the canyon produces vertical winds down the canyon walls in the evening of over 5 m/s. In contrast, during the early afternoon (MER landing time), horizontal winds at the proposed MER landing site are relatively calm, with little mean shear with height. This results from the proposed site being in a region of local divergence and the action of daytime convection. The nature of flow in Melas Chasma results in an interesting dual maximum in boundary convection and depth, with the usual daytime afternoon free convective maximum being joined by a mechanically forced nighttime boundary layer of almost 2 km depth. |
| Title: | Analysis of atmospheric mesoscale models for entry, descent, and landing |
| Authors: | Kass, D. M.; Schofield, J. T.; Michaels, T. I.; Rafkin, S. C. R.; Richardson, M. I.; Toigo, A. D. |
| Journal: | Journal of Geophysical Research, Volume 108, Issue E12, pp. ROV 31-1, CiteID 8090, DOI 10.1029/2003JE002065 |
| Publication Date: | Nov 2003 |
| Origin: | AGU |
| Keywords: | Planetary Sciences: Atmospheres-structure and dynamics, Planetary Sciences: Meteorology (3346), Planetary Sciences: Instruments and techniques, Planetology: Solar System Objects: Mars |
| Abstract Copyright: | (c) 2003: American Geophysical Union |
| DOI: | http://dx.doi.org/10.1029/2003JE002065 |
| Bibliographic Code: | 2003JGRE..108.8090K |
| Abstract: | Each Mars Exploration Rover (MER) is sensitive to the Martian winds encountered near the surface during the entry, descent, and landing (EDL) process. These winds are strongly influenced by local (mesoscale) conditions. In the absence of suitable wind observations, wind fields predicted by Martian mesoscale atmospheric models have been analyzed to guide landing site selection. In order to encompass the available models and render them useful to the EDL engineering team, a series of statistical techniques was applied to the model results. These analyses cover the high-priority landing sites during the expected landing times (1200-1500 LT). The number of sites studied is limited by the computational and analysis cost of the mesoscale models. The statistical measures concentrate on the effective mean wind (the wind as seen by the landing system) and on the vertical structure of the horizontal winds. Both aspects are potentially hazardous to the MER landing system. In addition, a number of individual wind profiles from the mesoscale model were processed into a form that can be used directly by the EDL Monte Carlo simulations. The statistical analysis indicates that the Meridiani Planum and Elysium landing sites are probably safe. The Gusev Crater and Isidis Basin sites may be safe, but further analysis by the EDL engineers will be necessary to quantify the actual risk. Finally, the winds at the Melas Chasma landing site (and presumably other Valles Marineris landing sites) are dangerous. While the statistical parameters selected for these studies were primarily of engineering and safety interest, the techniques are potentially useful for more general scientific analyses. One interesting result of the current analysis is that the depth of the convective boundary layer (and thus the resulting energy density) appears to be primarily driven by the existence of a well-organized mesoscale (or regional) circulation, primarily driven by large-scale topographic features at Mars. |
| Title: | Thermal Emission Imaging System (THEMIS) infrared observations of atmospheric dust and water ice cloud optical depth |
| Authors: | Smith, Michael D.; Bandfield, Joshua L.; Christensen, Philip R.; Richardson, Mark I. |
| Journal: | Journal of Geophysical Research, Volume 108, Issue E11, pp. 1-1, CiteID 5115, DOI 10.1029/2003JE002115 |
| Publication Date: | Nov 2003 |
| Origin: | AGU |
| Keywords: | Planetology: Solar System Objects: Mars, Planetary Sciences: Atmospheres-structure and dynamics, Planetary Sciences: Remote sensing, Meteorology and Atmospheric Dynamics: Remote sensing, Atmospheric Composition and Structure: Aerosols and particles (0345, 4801) |
| Abstract Copyright: | (c) 2003: American Geophysical Union |
| DOI: | http://dx.doi.org/10.1029/2003JE002115 |
| Bibliographic Code: | 2003JGRE..108.5115S |
| Abstract: | The Mars Odyssey spacecraft entered into Martian orbit in October 2001 and after successful aerobraking, began mapping in February 2002. Thermal infrared images taken by the Thermal Emission Imaging System (THEMIS) on board the Odyssey spacecraft allow for the quantitative retrieval of atmospheric dust and water ice aerosol optical depth. Data collected so far cover late northern winter, spring, and summer (Ls = 330°-160°). During this period, THEMIS observed the decay of a regional dust storm, a number of local dust storms along the edge of the retreating north polar cap, and the growth of the low-latitude aphelion water ice cloud belt. Data from THEMIS complements the concurrent Mars Global Surveyor Thermal Emission Spectrometer (TES) data by sampling a later local time (~1400 LT for TES versus ~1600-1730 LT for THEMIS) and by observing at much higher spatial resolution. Comparison of water ice optical depth in the aphelion cloud belt from THEMIS and TES shows a significantly higher optical depth in the late afternoon (THEMIS) than in the early afternoon (TES). |
| Title: | An assessment of the global, seasonal, and interannual spacecraft record of Martian climate in the thermal infrared |
| Authors: | Liu, Junjun; Richardson, Mark I.; Wilson, R. J. |
| Journal: | Journal of Geophysical Research, Volume 108, Issue E8, pp. 8-1, CiteID 5089, DOI 10.1029/2002JE001921 |
| Publication Date: | Aug 2003 |
| Origin: | AGU |
| Keywords: | Planetary Sciences: Atmospheres-structure and dynamics, Planetology: Solar System Objects: Mars, Meteorology and Atmospheric Dynamics: Climatology (1620), Meteorology and Atmospheric Dynamics: Planetary meteorology (5445, 5739) |
| Abstract Copyright: | (c) 2003: American Geophysical Union |
| DOI: | http://dx.doi.org/10.1029/2002JE001921 |
| Bibliographic Code: | 2003JGRE..108.5089L |
| Abstract: | Intercomparison of thermal infrared data collected by Mariner 9, Viking, and Mars Global Surveyor (MGS) is presented with a specific focus on air temperatures, dust opacities, and water ice opacities. Emphasis is placed on creating a uniform data set to most effectively reduce interinstrument biases and offsets. The annual cycle consistently shows a strong asymmetry about the equinoxes, with northern spring and summer exhibiting relatively low temperatures, very high year-to-year repeatability, and essentially no short-term (tens of days) variability. The globally averaged Martian nighttime air temperatures close annually to within a Kelvin during northern spring and summer. Daytime temperatures show more variability (3-6 K). The difference in repeatability of daytime versus nighttime temperatures is not understood. Viking and MGS air temperatures are essentially indistinguishable for this period, suggesting that the Viking and MGS eras are characterized by essentially the same climatic state. Southern summer is characterized by strong dust storm activity and hence strong year-to-year air temperature variability. Dust opacity shows a remarkable degree of interannual variability in southern spring and summer, associated with the intermittent activity of regional and planet-encircling dust storms, but exhibits high year-to-year repeatability in northern spring and summer. Specifically, late northern spring and early northern summer dust opacities appear to be completely insensitive to the occurrence (or not) of major dust storms in the previous southern spring or summer. We show that both Viking and MGS data sets exhibit significant (and similar) polar cap edge dust storm activity. The origins of the various major dust storms can be identified in the thermal infrared data from Viking and MGS, including the transport of dust from the northern autumn baroclinic zone into the southern hemisphere tropics, which has also been identified in visible imaging. We also note that the period around Ls = 225° is characterized by very high dust opacities associated with dust storm development or decay in every year thus far observed by spacecraft. Water ice opacities have been retrieved from Viking infrared data for the first time. We show that the northern spring and summer tropical cloud belt structure and evolution are essentially the same in each of the multiple years observed by Viking and MGS. Relatively subtle spatial features recur in the cloud belt from year to year, suggesting the influence of surface topography and thermophysical properties and a reasonably consistent supply of water vapor. The seasonal evolution of the tropical cloud belt through northern spring and summer is shown, with the only significant deviations between years occurring from Ls = 140° to 160°, where opacities fall in the second MGS year associated with a small dust storm. Polar hood clouds are observed in Viking and MGS observations with similar timing and extent. Interactions between dust and water ice were highlighted in the Hellas basin region during the southern spring 1977a and 2001 dust storms. The observations demonstrate that the Martian atmosphere executes a very “repeatable” annual cycle of atmospheric phenomena. However, a major part of this cycle is the occurrence of highly variable and potentially major dust storm events. After such dust storm events the atmosphere rapidly relaxes to its stable, repeatable state. |
| Title: | Sublimation of Mars’s southern seasonal CO2 ice cap and the formation of spiders |
| Authors: | Piqueux, Sylvain; Byrne, Shane; Richardson, Mark I. |
| Journal: | Journal of Geophysical Research, Volume 108, Issue E8, pp. 3-1, CiteID 5084, DOI 10.1029/2002JE002007 |
| Publication Date: | Aug 2003 |
| Origin: | AGU |
| Keywords: | Planetology: Solar System Objects: Mars, Planetary Sciences: Polar regions, Planetary Sciences: Erosion and weathering, Planetary Sciences: Surface materials and properties, Planetary Sciences: Remote sensing |
| Abstract Copyright: | (c) 2003: American Geophysical Union |
| DOI: | http://dx.doi.org/10.1029/2002JE002007 |
| Bibliographic Code: | 2003JGRE..108.5084P |
| Abstract: | In this paper we define and describe morphological features that have colloquially been termed “spiders” and map their distribution in the south polar region of Mars. We show that these features go through a distinct seasonal evolution, exhibiting dark plumes and associated fan-shaped deposits during the local defrosting of the seasonal cap. We have documented the seasonal evolution of the cryptic region and have found that spiders only occur within this terrain. These observations are consistent with a geyser-like model for spider formation. Association with the transparent (cryptic) portion of the seasonal cap is consistent with basal sublimation and the resulting venting of CO2 gas. Also consistent with such venting is the observation of dark fan-shaped deposits apparently emanating from spider centers. Spiders are additionally confined to the polar layered deposits presumably due to the poorly consolidated and easily eroded nature of their upper surface. |
| Title: | Principal modes of variability of Martian atmospheric surface pressure |
| Authors: | Leroy, S. S.; Yung, Y. L.; Richardson, M. I.; Wilson, R. J. |
| Journal: | Geophysical Research Letters, Volume 30, Issue 13, pp. 40-1, CiteID 1707, DOI 10.1029/2002GL015909 |
| Publication Date: | Jul 2003 |
| Origin: | AGU |
| Keywords: | Global Change: Atmosphere (0315, 0325), Global Change: Climate dynamics (3309), Meteorology and Atmospheric Dynamics: Planetary meteorology (5445, 5739), Planetary Sciences: Atmospheres-structure and dynamics |
| Abstract Copyright: | (c) 2003: American Geophysical Union |
| Bibliographic Code: | 2003GeoRL..30m..40L |
| Abstract: | An analysis of daily-to-interannual variability in the surface pressure field of the Martian nothern hemisphere as given by a Martian climate model is presented. In an empirical orthogonal function (EOF) decomposition, the dominant first two modes of variability comprise a zonal wavenumber 1 feature centered at 70 N latitude moving eastward with a period of 6 to 8 sols. This feature is a baroclinic wave and accounts for 53% of the northern hemisphere non-stationary surface pressure variability, and, when active, has an amplitude of up to 2% of local surface pressure. The third mode of the EOF decomposition is annular about the Martian north pole, is null southward of 70 N, and accounts for 7% of the northern hemisphere non-stationary surface pressure variability. The baroclinic wave (EOFs 1 & 2) is active during northern hemisphere winter and spring, consistent with models of the Martian atmospheric circulation, and the annular mode (EOF 3) is active only at the onset and demise of the baroclinic feature. When active, it is not uncommon for the annular mode to reside in either its positive or negative state stably for 20 to 30 sols. It is postulated that baroclinic waves with longitudinal wavenumber 2, 3, and 4 act as a pump for the annular mode. The annular mode should not be present in MGS TES data. |
| Title: | Morphology and Composition of the Surface of Mars: Mars Odyssey THEMIS Results |
| Authors: | Christensen, Philip R.; Bandfield, Joshua L.; Bell, James F.; Gorelick, Noel; Hamilton, Victoria E.; Ivanov, Anton; Jakosky, Bruce M.; Kieffer, Hugh H.; Lane, Melissa D.; Malin, Michael C.; McConnochie, Timothy; McEwen, Alfred S.; McSween, Harry Y.; Mehall, Greg L.; Moersch, Jeffery E.; Nealson, Kenneth H.; Rice, James W.; Richardson, Mark I.; Ruff, Steven W.; Smith, Michael D.; Titus, Timothy N.; Wyatt, Michael B. |
| Affiliation: | AA(Department of Geological Sciences, Arizona State University, Tempe, AZ 85287-6305, USA.), AB(Department of Geological Sciences, Arizona State University, Tempe, AZ 85287-6305, USA.), AC(Department of Astronomy, Cornell University, Ithaca, NY 14853-6801, USA.), AD(Department of Geological Sciences, Arizona State University, Tempe, AZ 85287-6305, USA.), AE(Hawaii Institute of Geophysics and Planetology, University of Hawaii, Honolulu, HI 96822, USA.), AF(Jet Propulsion Laboratory, Pasadena, CA 91109-8099, USA.), AG(LASP, University of Colorado, Boulder, CO 80309, USA.), AH(U.S. Geological Survey, Flagstaff, AZ 86001, USA.), AI(Planetary Science Institute, Phoenix, AZ 85032, USA.), AJ(Malin Space Science Systems, San Diego, CA 92191-0148, USA.), AK(Department of Astronomy, Cornell University, Ithaca, NY 14853-6801, USA.), AL(Lunar and Planetary Lab, University of Arizona, Tucson, AZ 85721, USA.), AM(Department of Geological Sciences, University of Tennessee, Kno! xville, TN 37996-1410, USA.), AN(Department of Geological Sciences, Arizona State University, Tempe, AZ 85287-6305, USA.), AO(Department of Geological Sciences, University of Tennessee, Knoxville, TN 37996-1410, USA.), AP(University of Southern California, Los Angeles, CA 90089, USA.), AQ(Department of Geological Sciences, Arizona State University, Tempe, AZ 85287-6305, USA.), AR(Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, CA 91125, USA.), AS(Department of Geological Sciences, Arizona State University, Tempe, AZ 85287-6305, USA.), AT(Goddard Space Flight Center, Greenbelt, MD 20771, USA.), AU(U.S. Geological Survey, Flagstaff, AZ 86001, USA.), AV(Department of Geological Sciences, Arizona State University, Tempe, AZ 85287-6305, USA.) |
| Journal: | Science, Volume 300, Issue 5628, pp. 2056-2061 (2003). |
| Publication Date: | Jun 2003 |
| Origin: | SCIENCE |
| Abstract Copyright: | (c) 2003: Science |
| Bibliographic Code: | 2003Sci…300.2056C |
| Abstract: | The Thermal Emission Imaging System (THEMIS) on Mars Odyssey has produced infrared to visible wavelength images of the martian surface that show lithologically distinct layers with variable thickness, implying temporal changes in the processes or environments during or after their formation. Kilometer-scale exposures of bedrock are observed; elsewhere airfall dust completely mantles the surface over thousands of square kilometers. Mars has compositional variations at 100-meter scales, for example, an exposure of olivine-rich basalt in the walls of Ganges Chasma. Thermally distinct ejecta facies occur around some craters with variations associated with crater age. Polar observations have identified temporal patches of water frost in the north polar cap. No thermal signatures associated with endogenic heat sources have been identified. |
| Title: | On the orbital forcing of Martian water and CO2 cycles: A general circulation model study with simplified volatile schemes |
| Authors: | Mischna, Michael A.; Richardson, Mark I.; Wilson, R. John; McCleese, Daniel J. |
| Journal: | Journal of Geophysical Research Planets, Volume 108, Issue E6, pp. 16-1, CiteID 5062, DOI 10.1029/2003JE002051 |
| Publication Date: | Jun 2003 |
| Origin: | AGU |
| Keywords: | Planetology: Solar System Objects: Mars, Planetary Sciences: Atmospheres-evolution, Planetary Sciences: Atmospheres-structure and dynamics, Planetary Sciences: Meteorology (3346), Atmospheric Composition and Structure: Planetary atmospheres (5405, 5407, 5409, 5704, 5705, 5707) |
| Abstract Copyright: | (c) 2003: American Geophysical Union |
| DOI: | http://dx.doi.org/10.1029/2003JE002051 |
| Bibliographic Code: | 2003JGRE..108.5062M |
| Abstract: | Variations in the Martian water and CO2 cycles with changes in orbital and rotational parameters are examined using the Geophysical Fluid Dynamics Laboratory Mars General Circulation Model. The model allows for arbitrary specification of obliquity, eccentricity, and argument of perihelion as well as the position and thickness of surface ice. Exchange of CO2 between the surface and atmosphere is modeled, generating seasonal cycles of surface ice and surface pressure. Water is allowed to exchange between the surface and atmosphere, cloud formation is treated, and both cloud and vapor are transported by modeled winds and diffusion. Exchange of water and CO2 with the subsurface is not allowed, and radiative effects of water vapor and clouds are not treated. The seasonal cycle of CO2 is found to become more extreme at high obliquity, as suggested by simple heat balance models. Maximum pressures remain largely the same, but the minima decrease substantially as more CO2 condenses in the more extensive polar night. Vapor and cloud abundances increase dramatically with obliquity. The stable location for surface ice moves equatorward with increasing obliquity, such that by 45° obliquity, water ice is stable in the tropics only. Ice is not spatially uniform, but rather found preferentially in regions of high thermal inertia or high topography. Eccentricity and argument of perihelion can provide a second-order modification to the distribution of surface ice by altering the temporal distribution of insolation at the poles. Further model simulations reveal the robustness of these distributions for a variety of initial conditions. Our findings shed light on the nature of near-surface, ice-rich deposits at midlatitudes and low-latitudes on Mars. |
| Title: | Numerical simulation of Martian dust devils |
| Authors: | Toigo, Anthony D.; Richardson, Mark I.; Ewald, Shawn P.; Gierasch, Peter J. |
| Journal: | Journal of Geophysical Research Planets, Volume 108, Issue E6, pp. 1-1, CiteID 5047, DOI 10.1029/2002JE002002 |
| Publication Date: | Jun 2003 |
| Origin: | AGU |
| Keywords: | Planetary Sciences: Meteorology (3346), Meteorology and Atmospheric Dynamics: Boundary layer processes, Meteorology and Atmospheric Dynamics: Convective processes, Meteorology and Atmospheric Dynamics: Mesoscale meteorology, Meteorology and Atmospheric Dynamics: Numerical modeling and data assimilation |
| Abstract Copyright: | (c) 2003: American Geophysical Union |
| DOI: | http://dx.doi.org/10.1029/2002JE002002 |
| Bibliographic Code: | 2003JGRE..108.5047T |
| Abstract: | Large eddy simulations of vertical convective vortices and dust devils in the Martian convective boundary layer are presented, employing a version of the Mars MM5 mesoscale model, adapted to use periodic boundary conditions and run at resolutions of 10 to 100 m. The effects of background horizontal wind speed and shear on dust devil development are studied in four simulations, each extending over the daytime portion of one Martian day. The general vorticity development in all cases is similar, with roughly equal positive and negative vorticity extrema. Two dust devils were found to develop in the highest wind speed case and in a case run without background wind. The dust devil structures were found to agree well qualitatively with terrestrial dust devil observations, including the prediction of greatly diminished vertical velocities in the vortex core. Thermodynamic scaling theory of dust devils was found to provide good prediction of the relationship between central pressure and temperature in the modeled vortices. Examination of the turbulent kinetic energy budgets suggests balance between buoyancy generation and loss through dissipation and transport. The vorticity for the dust devils is provided by twisting of horizontal vorticity into the vertical. The horizontal vorticity originates from horizontal variations in temperature at the lower boundary (thermal buoyancy). While the horizontal winds generated by the modeled dust devils were likely insufficient to lift dust, this study provides a solid starting point for dynamic modeling of what may be an important component of the Martian dust cycle. |
| Title: | Cyclones, tides, and the origin of a cross-equatorial dust storm on Mars |
| Authors: | Wang, Huiqun; Richardson, Mark I.; Wilson, R. John; Ingersoll, Andrew P.; Toigo, Anthony D.; Zurek, Richard W. |
| Journal: | Geophysical Research Letters, Volume 30, Issue 9, pp. 41-1, CiteID 1488, DOI 10.1029/2002GL016828 |
| Publication Date: | May 2003 |
| Origin: | AGU |
| Keywords: | Planetary Sciences: Atmospheres-structure and dynamics, Planetology: Solar System Objects: Mars |
| Abstract Copyright: | (c) 2003: American Geophysical Union |
| DOI: | http://dx.doi.org/10.1029/2002GL016828 |
| Bibliographic Code: | 2003GeoRL..30i..41W |
| Abstract: | We investigate the triggering mechanism of a cross-equatorial dust storm observed by Mars Global Surveyor in 1999. This storm, which had a significant impact on global mean temperatures, was seen in visible and infrared data to commence with the transport of linear dust fronts from the northern high latitudes into the southern tropics. However, other similar transport events observed in northern fall and winter did not lead to large dust storms. Based on off-line Lagrangian particle transport analysis using a high resolution Mars general circulation model, we propose a simple explanation for the diurnal, seasonal and interannual variability of this type of frontal activity, and of the resulting dust storms, that highlights the cooperative interaction between northern hemisphere fronts associated with low pressure cyclones and tidally-modified return branch of the Hadley circulation. |
| Title: | Water ice clouds in the Martian atmosphere: General circulation model experiments with a simple cloud scheme |
| Authors: | Richardson, Mark I.; Wilson, R. John; Rodin, Alexander V. |
| Journal: | Journal of Geophysical Research (Planets), Volume 107, Issue E9, pp. 2-1, CiteID 5064, DOI 10.1029/2001JE001804 |
| Publication Date: | Sep 2002 |
| Origin: | AGU |
| Keywords: | Planetology: Solar System Objects: Mars, Planetary Sciences: Meteorology (3346), Atmospheric Composition and Structure: Cloud physics and chemistry, Global Change: Climate dynamics (3309), Atmospheric Composition and Structure: Planetary atmospheres (5405, 5407, 5409, 5704, 5705, 5707) |
| Abstract Copyright: | (c) 2002: American Geophysical Union |
| DOI: | http://dx.doi.org/10.1029/2001JE001804 |
| Bibliographic Code: | 2002JGRE..107.5064R |
| Abstract: | We present the first comprehensive general circulation model study of water ice condensation and cloud formation in the Martian atmosphere. We focus on the effects of condensation in limiting the vertical distribution and transport of water and on the importance of condensation for the generation of the observed Martian water cycle. We do not treat cloud ice radiative effects, ice sedimentation rates are prescribed, and we do not treat interactions between dust and cloud ice. The model generates cloud in a manner consistent with earlier one-dimensional (1-D) model results, typically evolving a uniform (constant mass mixing ratio) vertical distribution of vapor, which is capped by cloud at the level where the condensation point temperature is reached. Because of this vertical distribution of water, the Martian atmosphere is generally very far from fully saturated, in contrast to suggestions based upon interpretation of Viking data. This discrepancy results from inaccurate representation of the diurnal cycle of air temperatures in the Viking Infrared Thermal Mapper (IRTM) data. In fact, the model suggests that only the northern polar atmosphere in summer is consistently near its column-integrated holding capacity. In this case, the column amount is determined primarily by the temperature of the northern polar ice cap. Comparison of the water cycle generated by the model with and without atmospheric ice condensation and precipitation shows two major roles for water ice cloud. First, clouds are essential to the observed rapid return of atmospheric water to the surface in late northern summer, as ice sedimentation forces the water column to shrink in response to the downward motion of the condensation level, concentrating water near surface sinks. Second, ice sedimentation limits the amount of water that is transported between the hemispheres through the Hadley circulation. This latter effect is used to greatly improve the model simulation of the annual water cycle by increasing ice sedimentation rates. The model is thus shown to be able to reasonably reproduce the annual cycles of vapor and ice cloud as compared to Viking data. In addition, the model is shown able to reproduce near-instantaneous maps of water ice derived from Hubble Space Telescope images. The seasonal evolution of the geographic distribution of water ice compares reasonably well with Viking and Mars Global Surveyor (MGS) Mars Orbiter Laser Altimeter (MOLA) observations, except in the prediction of a weak tropical cloud belt in southern summer. Finally, it is shown that the tropical cloud belt is generated in the model by the cooling of water vapor entrained in the upwelling branch of the Hadley cell. Decline of the tropical cloud belt in mid northern summer is shown to be related to an increase in air temperatures, rather than to decreases in water vapor supply or the vigor of Hadley cell ascent. By equinox, the cloud belt experiences a second major decline event, this time due to a reduction in vapor supply. The ability of the model to emulate many aspects of observed cloud behavior is encouraging, as is the ability of enhanced ice sedimentation to improve the overall quality of the water cycle simulation. However, significant work remains to be done before all observational constraints can be matched simultaneously. Specifically, in order for the generally good fit to all other data to be attained, cloud ice particle sizes about an order of magnitude too large must be used. |
| Title: | A first look at dust lifting and dust storms near the south pole of Mars with a mesoscale model |
| Authors: | Toigo, Anthony D.; Richardson, Mark I.; Wilson, R. John; Wang, Huiqun; Ingersoll, Andrew P. |
| Journal: | Journal of Geophysical Research (Planets), Volume 107, Issue E7, pp. 4-1, CiteID 5050, DOI 10.1029/2001JE001592 |
| Publication Date: | Jul 2002 |
| Origin: | AGU |
| Keywords: | Meteorology and Atmospheric Dynamics: Mesoscale meteorology, Meteorology and Atmospheric Dynamics: Planetary meteorology (5445, 5739), Meteorology and Atmospheric Dynamics: Polar meteorology, Planetary Sciences: Meteorology (3346), Planetology: Solar System Objects: Mars |
| Abstract Copyright: | (c) 2002: American Geophysical Union |
| DOI: | http://dx.doi.org/10.1029/2001JE001592 |
| Bibliographic Code: | 2002JGRE..107.5050T |
| Abstract: | Surface wind stresses and dust lifting in the south polar region of Mars are examined with a three-dimensional numerical model. The focus of this study is the middle to late southern spring period when cap-edge dust lifting events are observed. Mesoscale model simulations of high southern latitudes are conducted at three dates within this season (Ls = 225°, 255°, and 310°). Assuming that dust injection is related to the saltation of sand-sized grains or aggregates, the Mars MM5 mesoscale model predicts surface wind stresses of sufficient strength to initiate movement of sand-sized particles (~100 μm), and hence dust lifting, during all three periods. The availability of dust and/or sand-sized particles is not addressed within this study. Instead, the degree to which the existence of sufficiently strong winds limit dust injection is examined. By eliminating forcing elements from the model, the important dynamical modes generating high wind stresses are isolated. The direct cap-edge thermal contrast (and topographic slopes in some locations) provides the primary drive for high surface wind stresses at the cap edge, while sublimation flow is not found to be particularly important, at these three dates. Simulations in which dust is injected into the lowest model layer when wind stresses exceed a threshold show similar patterns of atmospheric dust to those seen in recent observations. Comparison between these simulations and those without active dust injection shows no signs of consistent positive or negative feedback due to dust clouds on the surface wind stress fields during the late spring season examined here. |
| Title: | A mesoscale model for the Martian atmosphere |
| Authors: | Toigo, Anthony D.; Richardson, Mark I. |
| Journal: | Journal of Geophysical Research (Planets), Volume 107, Issue E7, pp. 3-1, CiteID 5049, DOI 10.1029/2000JE001489 |
| Publication Date: | Jul 2002 |
| Origin: | AGU |
| Keywords: | Meteorology and Atmospheric Dynamics: Mesoscale meteorology, Meteorology and Atmospheric Dynamics: Numerical modeling and data assimilation, Meteorology and Atmospheric Dynamics: Planetary meteorology (5445, 5739), Planetary Sciences: Meteorology (3346), Planetology: Solar System Objects: Mars |
| Abstract Copyright: | (c) 2002: American Geophysical Union |
| DOI: | http://dx.doi.org/10.1029/2000JE001489 |
| Bibliographic Code: | 2002JGRE..107.5049T |
| Abstract: | The Pennsylvania State University/National Center for Atmosphere Research Mesoscale Model Version 5 (MM5) has been converted for use on Mars. Modifications are based on schemes implemented in the Geophysical Fluid Dynamics Laboratory Mars General Circulation Model (GCM). Validation of the Mars MM5 is conducted by comparison to the Mars GCM, examining the large-scale dynamics in the two models. Agreement between the two models on similar scales (a few hundred kilometers) is good. Validation is also performed against both Viking Landers and Mars Pathfinder meteorological observations with the model run at higher vertical (lowest level at 1.6 m) and horizontal resolution (a few kilometers). We find reasonable agreement with near-surface air temperature, pressure, and wind direction observations, with caveats. The results demonstrate that the model accurately simulates surface heat balance and the propagation of global thermal tides. However, wind speeds are underpredicted. The model generates the correct phasing of wind speeds with local time at the Viking Lander 2 site during winter but does not generate the correct phasing at the other sites or seasons. We examined the importance of slopes and global tides in generating the diurnal cycle of winds at the lander sites. We find that tides are at least as important as slopes, in contrast to previous studies. This study suggests that when used in combination with a GCM, the Mars MM5 promises to be a powerful tool for the investigation of processes central to the Martian climate on scales from hundreds of kilometers to tens of meters. |
| Title: | Investigation of the nature and stability of the Martian seasonal water cycle with a general circulation model |
| Authors: | Richardson, Mark I.; Wilson, R. John |
| Journal: | Journal of Geophysical Research (Planets), Volume 107, Issue E5, pp. 7-1, CiteID 5031, DOI 10.1029/2001JE001536 |
| Publication Date: | May 2002 |
| Origin: | AGU |
| Keywords: | Planetary Sciences: Meteorology (3346), Planetary Sciences: Polar regions, Planetary Sciences: Atmospheres-structure and dynamics, Planetology: Solar System Objects: Mars |
| Abstract Copyright: | (c) 2002: American Geophysical Union |
| DOI: | http://dx.doi.org/10.1029/2001JE001536 |
| Bibliographic Code: | 2002JGRE..107.5031R |
| Abstract: | We describe the first use of a general circulation model to study the Martian water cycle. Water is treated as a passive tracer, except for ice-albedo coupling. The model is used to assess which mechanisms and water reservoirs are critical to the seasonal evolution of water and specifically the attainment of an interannually repeatable steady state. The model comes to a reasonable steady state with active surface ice and atmospheric vapor and ice reservoirs. A regolith is not necessary. The mechanism of equilibration results from independent parameters controlling the transport of water between the northern polar and the extratropical atmospheres at different seasons. Water export from the northern summer pole results from weak mixing across a strong vapor gradient, dependent upon northern cap temperatures. Import at other seasons depends on stronger mixing and weak vapor gradients, which are history dependent. Equilibration is achieved when the fluxes balance, minus a small net loss to the south. We find that with a southern residual CO2 cap, the water cycle cannot be completely closed. We conclude that the northern summer cap temperature determines the bulk humidity of the atmosphere, all else being equal. We proceed to show that a water cap exposed in southern summer would be unstable with respect to the north for dynamical as well as thermal reasons. At high obliquity (45°), much higher vapor abundances result in more widespread surface ice with seasonal ice caps overlapping in the equinoctial subtropics, producing year-round stability of water ice just north of the equator. |
| Title: | A topographically forced asymmetry in the martian circulation and climate |
| Authors: | Richardson, Mark I.; Wilson, R. John |
| Affiliation: | AA(Division of Geological and Planetary Sciences, California Institute of Technology, MC 150-21, Pasadena, California 91125, USA), AB(Geophysical Fluid Dynamics Laboratory, National Oceanic and Atmospheric Administration, PO Box 308, Princeton, New Jersey 08542, USA) |
| Journal: | Nature, Volume 416, Issue 6878, pp. 298-301 (2002). |
| Publication Date: | Mar 2002 |
| Origin: | NATURE |
| Abstract Copyright: | (c) 2002: Nature |
| Bibliographic Code: | 2002Natur.416..298R |
| Abstract: | Large seasonal and hemispheric asymmetries in the martian climate system are generally ascribed to variations in solar heating associated with orbital eccentricity. As the orbital elements slowly change (over a period of >104 years), characteristics of the climate such as dustiness and the vigour of atmospheric circulation are thought to vary, as should asymmetries in the climate (for example, the deposition of water ice at the northern versus the southern pole). Such orbitally driven climate change might be responsible for the observed layering in Mars’ polar deposits by modulating deposition of dust and water ice. Most current theories assume that climate asymmetries completely reverse as the angular distance between equinox and perihelion changes by 180°. Here we describe a major climate mechanism that will not precess in this way. We show that Mars’ global north-south elevation difference forces a dominant southern summer Hadley circulation that is independent of perihelion timing. The Hadley circulation, a tropical overturning cell responsible for trade winds, largely controls interhemispheric transport of water and the bulk dustiness of the atmosphere. The topography therefore imprints a strong handedness on climate, with water ice and the active formation of polar layered deposits more likely in the north. |
| Title: | Martian surface winds: Insensitivity to orbital changes and implications for aeolian processes |
| Authors: | Fenton, Lori K.; Richardson, Mark I. |
| Journal: | Journal of Geophysical Research, Volume 106, Issue E12, p. 32885-32902 |
| Publication Date: | Dec 2001 |
| Origin: | AGU |
| Keywords: | Meteorology and Atmospheric Dynamics: Planetary meteorology, Planetology: Solid Surface Planets: Atmospheres-evolution, Planetology: Solid Surface Planets: Erosion and weathering, Planetology: Solar System Objects: Mars |
| Abstract Copyright: | (c) 2001: American Geophysical Union |
| DOI: | http://dx.doi.org/10.1029/2000JE001407 |
| Bibliographic Code: | 2001JGR…10632885F |
| Abstract: | Aeolian features observed on the surface of Mars provide insight into current, and potentially past, surface wind systems. In some cases the features are clearly transient and related to the lifting and settling of atmospheric dust. Other features, like dunefields, yardangs, and ventifacts, are more persistent and likely require significant time to form. In this study we analyze the observed directions of selected aeolian features with the aid of the Geophysical Fluid Dynamics Laboratory Mars general circulation model (GCM). Initially, we examine bright and dark streaks which have been observed to form in association with global dust storms. The ability to match these features with Mars GCM wind directions provides an important validation of the model. More important, we are able to define best fit seasons and local times for both types of features which provide the basis for extension and modification of the Veverka et al. [1981] model of bright and dark dust streak formation. In addition these best fit times correspond well with the dark streak “wind storm” model of Magalhães and Young [1995]. The primary focus of this paper is to provide constraints on the range of mechanisms proposed to explain inconsistencies between current wind direction patterns and long-term wind indicators (for example, the misalignment of rock tail and ventifact orientations at the Mars Pathfinder landing site). Specifically, we assess whether changes in planetary obliquity, precession, or global dust opacity could significantly alter patterns of surface wind directions. In all cases we find the seasonal and annual average wind direction patterns to be highly invariable. While changes in the dust loading (hence the partitioning of solar absorption between the surface and atmosphere) and in the surface latitude of maximum solstitial insolation cause the vigor of the large-scale circulation to increase (especially the Hadley cell), the spatial patterns of the surface wind orientations remain essentially unchanged. In the case of perihelion during northern summer (opposite of the current perihelion position), the northern summer Hadley cell remains weaker than the southern summer cell despite the strengthened heating in the northern hemisphere. Taken together, these results cast significant doubt on orbital explanations for surface wind changes. It is thus suggested that significant changes in topography (e.g., Tharsis uplift, true polar wander) or climate (e.g., the existence of a significantly thicker atmosphere or an ocean at some point in the past) are more likely explanations for long-term wind indicators such as the ventifact orientations at the Mars Pathfinder landing site. |
| Title: | The martian atmosphere during the Viking mission, I. Infrared measurements of atmospheric temperatures revisited |
| Authors: | Wilson, R. J.; Richardson, M. I. |
| Journal: | Icarus, Vol. 145, p. 555-579 (2000) |
| Publication Date: | Jun 2000 |
| Origin: | ICAR |
| Keywords: | Mars Atmosphere: Temperatures |
| DOI: | http://dx.doi.org/10.1006/icar.2000.6378 |
| Bibliographic Code: | 2000Icar..145..555J |
| Abstract: | The Viking Infrared Thermal Mapper 15-μm channel brightness temperature observations (IRTM T15) provide extensive spatial and temporal coverage of Martian atmospheric temperatures on diurnal to seasonal time scales. The 15-μm channel was designed so that these temperatures would be representative of a deep layer of atmosphere centered at 0.5 mb (~25 km). A re-examination of the IRTM data indicates that the 15-μm channel was additionally sensitive to surface radiance so that air temperature determinations (nominal T15) are significantly biased when the thermal contrast between the surface and atmosphere is large. This bias is suggested by the strong correlation between the diurnal variation of tropical T15 and surface temperatures for non-dust-storm conditions. The authors show that numerical modeling of the thermal tides provides a basis for distinguishing between the surface and atmospheric contributions to IRTM T15 and thus allows the atmospheric component to be estimated. The resulting bias amounts to a ~15-K offset for midday atmospheric temperatures at subsolar latitudes during relatively clear periods and is negligible at night. |
| Title: | Seasonal variation of aerosols in the Martian atmosphere |
| Authors: | Toigo, Anthony D.; Richardson, Mark I. |
| Journal: | Journal of Geophysical Research, Volume 105, Issue E2, p. 4109-4122 |
| Publication Date: | Feb 2000 |
| Origin: | AGU |
| Keywords: | Atmospheric Composition and Structure: Aerosols and particles, Planetology: Solid Surface Planets: Meteorology, Planetology: Solar System Objects: Mars |
| Abstract Copyright: | (c) 2000: American Geophysical Union |
| DOI: | http://dx.doi.org/10.1029/1999JE001132 |
| Bibliographic Code: | 2000JGR…105.4109T |
| Abstract: | Reanalysis of Viking Lander (VL) visible and Viking Orbiter infrared optical depth measurements shows that the visible to infrared ratio of total extinction opacity varies with season. The ratio is near to its previously reported constant value, 2.5, during dust storm periods and higher during northern spring and summer. The increase in ratio is hypothesized to be due to seasonally varying water ice haze, which produces a higher optical depth in the visible than in the infrared. This differs significantly from previous analyses of VL visible opacities which have assumed that only dust contributes to the optical depth measured during the early afternoon. Consequently we suggest that the Martian atmosphere is clearer of dust, especially during northern spring and summer, than previously suggested based upon VL data. We find dust visible optical depths of 0.1-0.4 during the northern spring and summer seasons, compared to previous estimates of 0.4-0.6. We also find that water ice hazes can provide roughly 50% of the total visible opacity in these seasons. For southern spring and summer, dust optical depths are more variable, but generally >=0.4, with water ice opacity <=0.1. The data suggest water ice optical depths are slightly higher and peak earlier (Ls=80°-90°) at VL1 than at VL2 (Ls=115°-130°). We estimate average northern summer water (daytime minimum) ice masses to be roughly 0.1-0.5 precipitable microns, depending on the assumed particle size distribution and hence 1-5% of the total water column. The observation of significant and previously unrecognized amounts of water ice haze suggests a larger role for water in controlling atmospheric heating rates and the vertical distribution of dust and water vapor than has been widely accepted to date. |
| Title: | Comparison of microwave and infrared measurements of Martian atmospheric temperatures – Implications for short-term climate variability |
| Authors: | Richardson, Mark I. |
| Affiliation: | AA(California, Univ., Los Angeles) |
| Journal: | Journal of Geophysical Research, vol. 103, p. 5911 |
| Publication Date: | Mar 1998 |
| Origin: | STI |
| Keywords: | TEMPERATURE MEASUREMENT, MARS ATMOSPHERE, ATMOSPHERIC TEMPERATURE, CLIMATE CHANGE, VIKING ORBITER SPACECRAFT, INFRARED DETECTORS, MICROWAVE SENSORS, THERMAL MAPPING, MARINER 9 SPACE PROBE |
| Bibliographic Code: | 1998JGR…103.5911R |
| Abstract: | This paper presents the first comparison of simultaneous Viking infrared and ground-based microwave measurements of the Martian atmosphere. The data are examined in order to investigate a 15-20 K difference between microwave and Viking measurements of mid-level (10-40 km) air temperature. These data have been used by Clancy et al. (1990) to suggest that the Martian atmosphere is generally cooler and clearer than observed during the Viking era. This study suggests that the 15-20 K difference, which is most apparent during the non-’dust-storm’ seasons, is not a real temperature difference, but instead results from a disagreement between the measurement techniques. The existence of this instrumental bias implies that the Martian climate has not substantially changed since the Viking era. |
| Title: | New dust opacity mapping from Viking Infrared Thermal Mapper data |
| Authors: | Martin, T. Z.; Richardson, M. I. |
| Affiliation: | AA(JPL, Pasadena, CA), AB(Imperial College of Science, Technology, and Medicine, London, England) |
| Journal: | Journal of Geophysical Research (ISSN 0148-0227), vol. 98, no. E6, p. 10,941-10,949. |
| Publication Date: | Jun 1993 |
| Origin: | STI; LPI [AN-930515%J] |
| Keywords: | DUST STORMS, INFRARED IMAGERY, MARS ATMOSPHERE, OPACITY, THERMAL MAPPING, VIKING MARS PROGRAM, ANNUAL VARIATIONS, BRIGHTNESS TEMPERATURE, SATELLITE IMAGERY, MARS, DUST, OPACITY, SPACECRAFT OBSERVATIONS, VIKING MISSIONS, ORBITERS, WAVELENGTHS, INFRARED, IRTM INSTRUMENT, ATMOSPHERE, MAPPING, ORIGIN, DUST STORMS, DESCRIPTION, FORMATION, COMPARISON, THERMAL PROPERTIES, TEMPERATURE, DISTRIBUTION, LATITUDE |
| Bibliographic Code: | 1993JGR….9810941M |
| Abstract: | Global dust opacity mapping for Mars has been carried forward using the approach described by Martin (1986) for Viking IR Thermal Mapper data. New maps are presented for the period from the beginning of Viking observations, until Ls 210 deg in 1979 (1.36 Mars years). This range includes the second and more extensive planet-encircling dust storm observed by Viking, known as storm 1977b. Improvements in approach result in greater time resolution and smaller noise than in the earlier work. A strong local storm event filled the Hellas basin at Ls 170 deg, prior to the 1977a storm. Dust is retained in equatorial regions following the 1977b storm far longer than in mid-latitudes. Minor dust events appear to raise the opacity in northern high latitudes during northern spring. Additional mapping with high time resolution has been done for the periods of time near the major storm origins in order to search for clues to the mechanism of storm initiation. The first evidence of the start of the 1977b storm is pushed back to Ls 274.2 deg, preceding signs of the storm in images by about 15 hours. |
