Aeolis Research | Publications 2002-2003

2003

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 http://bit.ly/YkDBy5
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 http://bit.ly/TgqZBE
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 http://bit.ly/Sps3Vb
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 http://bit.ly/TmQ7Hw
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 http://bit.ly/V9lDhk
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
DOI:	http://dx.doi.org/10.1029/2002GL015909 http://bit.ly/2nLYq4V
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
DOI:	http://dx.doi.org/10.1126/science.1080885 http://bit.ly/2oh8Z3M
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 http://bit.ly/TZHMrz
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 http://bit.ly/QmcQWC
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 http://bit.ly/YkEFlz
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.

2002

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 http://bit.ly/Wsp8L4
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 http://bit.ly/YkF2N4
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 http://bit.ly/U8irOw
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 http://bit.ly/S8T0N3
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
DOI:	http://dx.doi.org/10.1038/416298a http://bit.ly/2oN6FlJ
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.

Abstracts 2002-2003