Mars General Circulation Model Research Articles

Retrievals of vertical distribution of Martian water vapor from combined day and night MGS TES nadir spectra

Vertical distribution of water vapor in the Martian lower atmosphere (0–40 km) is an important characteristic of the Martian water cycle. It reflects a complex interplay between various processes shaping the contemporary water cycle, including atmospheric transport, formation of water ice clouds, sublimation of surface frost, and possible interaction with the subsurface. Despite the growing dataset of water vapor observations, there is yet no comprehensive climatology of the vertical distribution of vapor. Limb and solar occultation observations that are typically used to retrieve vapor vertical distribution are much less numerous than nadir observations and are available for limited seasons and locations. We propose a new methodology to retrieve vertical distribution of water vapor in the Martian lower atmosphere using only nadir data. The methodology is based on the observation that infrared spectra collected over same location during different parts of day are sensitive to water vapor in different parts of the atmosphere. We validate our new methodology by applying it to infrared spectra simulated for realistic Mars environments created with Mars General Circulation Model (GCM). These tests show that vertical profiles of vapor can be recovered with accuracy ~20–40%, which is comparable to accuracy of limb and occultation observations. Importantly, the new retrieval algorithm can constrain near-surface (0–10 km) vapor abundances that cannot be observed by limb and occultation techniques. Application of this new methodology to a large dataset on Martian nadir spectra, such as the one collected by the Thermal Emission Spectrometer (TES) onboard Mars Global Surveyor (MGS) during its mission in 1999–2004, can result in the development of the detailed climatology of vapor vertical distribution on Mars. As an initial step toward this goal, we apply the new retrieval methodology to a subset of nadir spectra collected by MGS TES during one Martian year. The retrieved vapor profiles are qualitatively consistent with vapor distributions predicted by the GCM for different seasons. Differences between retrieved and simulated profiles can be interpreted as reflecting wetter Martian atmosphere and weaker atmospheric transport, during some seasons. Retrieved vapor distribution during southern summer suggests disruption of atmospheric vapor transport into southern extra-tropics following a global dust storm.

A modern-day Mars climate in the Met Office Unified Model: dry simulations

Abstract. We present results from the Met Office Unified Model (UM), a world-leading climate and weather model, adapted to simulate a dry Martian climate. We detail the adaptation of the basic parameterisations and analyse results from two simulations, one with radiatively active mineral dust and one with radiatively inactive dust. These simulations demonstrate how the radiative effects of dust act to accelerate the winds and create a mid-altitude isothermal layer during the dusty season. We validate our model through comparison with an established Mars model, the Laboratoire de Météorologie Dynamique planetary climate model (PCM), finding good agreement in the seasonal wind and temperature profiles but with discrepancies in the predicted dust mass mixing ratio and conditions at the poles. This study validates the use of the UM for a Martian atmosphere, highlights how the adaptation of an Earth general circulation model (GCM) can be beneficial for existing Mars GCMs and provides insight into the next steps in our development of a new Mars climate model.

Diurnal waves forced by horizontal convergence of near-surface winds on Mars

Boundary-layer winds near steeply sloped topography excite a distinct type of atmospheric wave. Basic properties of the waves were determined through analysis of 7 Mars years of temperature profiles from the Mars Climate Sounder on Mars Reconnaissance Orbiter. A more complete understanding of the waves was derived from a simulation with the NASA Ames Mars General Circulation Model. This type of wave appears in the tropics in the vicinity of conspicuous surface features, such as large volcanoes and the rim of Isidis Planitia. The amplitude is typically 5–10 K, the vertical wavelength is about 40 km, the zonal wavelength is about 1400 km, and the zonal phase speed relative to the surface is about 25 m s−1. The wave forcing comes from horizontal convergence of the near-surface winds, which generates a daily surge in the vertical winds. These convergence zones were not previously recognized as an important source of atmospheric waves on Mars. Strong forcing occurs only within a limited range of local time, producing wave packets (diurnal pulses) rather than steady oscillations. Waves are present throughout the year and their properties vary with season. Near the solstices, the wave amplitude is largest in the tropics of the summer hemisphere, where the convergence zones are stronger than in the winter hemisphere. The diurnal-mean zonal winds, which vary with latitude and season, control the direction of propagation of the predominant waves through filtering by critical levels.

Impacts of Gravity Waves in the Martian Thermosphere: The Mars Global Ionosphere‐Thermosphere Model Coupled With a Whole Atmosphere Gravity Wave Scheme

AbstractGravity waves are a key mechanism that facilitates coupling between the lower and upper atmosphere of Mars. In order to better understand the mean, large‐scale impacts of gravity waves on the thermosphere, a modern whole atmosphere, nonlinear, non‐orographic gravity wave parameterization scheme has been incorporated into a three‐dimensional ground‐to‐exosphere Mars general circulation model, the Mars Global Ionosphere‐Thermosphere Model (M‐GITM). M‐GITM simulations utilizing the gravity wave parameterization indicate that significant gravity wave momentum is deposited in the thermosphere, especially within the altitude range of 90–170 km. This impacts the winds in the thermosphere; in particular, M‐GITM simulations show a decrease in speed of the wind maximum in the summer hemisphere by over a factor of two. Gravity wave effects also impact the temperatures above 120 km in the model, producing a cooler simulated thermosphere at most latitudes. M‐GITM results were also compared to upper atmospheric temperature and wind data sets from the MAVEN (Mars Atmosphere and Volatile Evolution) spacecraft. Some aspects of wind data‐model comparisons improved once the gravity wave scheme was added to M‐GITM; furthermore, a cooler temperature profile produced by these new M‐GITM simulations for the MAVEN Deep Dip 2 observational campaign resulted in a closer data‐model comparison, particularly above 180 km. Overall, these modeling results show that gravity waves play an important role for the energy and momentum budget of the Martian thermosphere.

The Dust Cycle on Mars at Different Orbital Distances from the Sun: An Investigation of the Impact of Radiatively Active Dust on Land Planet Climate

The dust cycle is the dominant driver of meteorology and climate on present-day Mars. Despite this, few studies have investigated the impact of dust interacting with incoming stellar radiation on the climate, habitability, and potential spectral signature of Mars-like exo-land planets. Dust availability is positively correlated with increasing soil aridity and therefore dust has significant potential to modify dynamics on dry land planets. In this work, we use an advanced Mars general circulation model to study the coupling between radiatively active dust and land planet climate at different stellar heating rates or planetary orbits. We find that radiatively active dust can significantly modify land planet climate. At Earth orbit, dust with optical properties similar to present-day Mars warms the planetary surface above 273 K and augments both the zonal mean circulation and the thermal tide, and in particular the semidiurnal component. As dust accumulates, peak heating rises off the planetary surface and the most active regions of dust lifting shift from the summer to winter hemisphere. Simulated spectra are nearly featureless across all wavelengths. We find that in order to accurately assess the climate and habitability of land planets it is critical to carefully consider that potential atmospheric dust budget and its radiative impact.

The Effect of Model Resolution on the Vertical and Temporal Variation in the Simulated Martian Climate

To study the impact of model horizontal resolution on the simulated climate of Mars, we increased the model resolution of the Mars general circulation model MarsWRF from the commonly used 5° × 5° (standard resolution, SR) to 3° × 3° (high resolution, HR). We applied an interactive dust scheme to parameterize the dust-lifting process and investigated the effect of model resolution from three aspects: (1) temporal variation; (2) horizontal distribution; and (3) vertical distribution. From the results of the simulations, we obtained the following conclusions: (1) The seasonal variation in some zonal-mean fields such as the column optical depth and T15 temperature could be reasonably simulated in both the SR and HR simulations, and the results were similar. (2) The effect of resolution on the horizontal distribution of the climate fields was significant at some regions with complicated terrain. (3) The HR simulation could be different from the SR simulation in the vertical dynamic field and thermal field. To obtain more accurate simulation results, it is recommended to use a higher resolution simulation when the vertical distribution is a major concern in the study.

Connections between the Transient Polar Warming and Solstitial Pause on Mars

Observations show two different transient atmospheric events around the northern winter solstice on Mars: a warming of the polar lower atmosphere (100–10 Pa) and a reduction in the near-surface wave activity. Here we examine the cause of, and connections between, these two events, and how their occurrence may have changed in past climates using a suite of Mars general circulation model simulations. These simulations show that the polar warming and pause in wave activity are connected, and they occur when there are sufficiently large dust heating rates in the southern (summer) high latitudes, which drive an expansion of the downwelling branch of the Hadley cell into the northern polar region. This causes a poleward shift and weakening of the jet, a warming of the polar lower atmosphere, and reduced baroclinic instability and waves near the surface. The occurrence and strength of the polar warming and wave activity pause increase with obliquity and dust optical depth, with a stronger dependence on obliquity. In past climates with low obliquity the warming and pause are unlikely to occur, or will be very weak, whereas during times of high obliquity they will likely be strong and occur every winter, unless the atmosphere is nearly free of dust.

Simulation of dust activities in the southern high latitudes of Mars

Annual occurrence of dust activities in the southern high-latitude region around the southern solstice period have been observed for many Martian years. Theses dust events occur near the southern cap-edge region and play an important role in the observed dust climate. However, they generally cannot be simulated in the existing Mars general circulation models. In this study, an approach of parameterization has been applied to the Mars climate model MarsWRF in which the dust lifting threshold stress is adjusted in according to the surface temperature difference between the regolith and the ice in the southern polar region. By this approach, dust events in the southern cap-edge region have been simulated around the southern solstice period. As a result, the simulated temperature in the southern high-latitude region is increased and the resulting vertical temperature profile is closer to that from observation. In addition, westward propagating dust events as observed in a previous study have been simulated, with a propagating speed similar to that observed. Results of the numerical experiments suggest that the flow associated with the sublimation of the CO 2 ice in the southern cap edge is important to the occurrence and propagation of these dust events in this region. • Dust activities near the southern cap edge have been simulated with the interactive dust approach. • A parameterization scheme of cap-edge dust is proposed. • Generation of cap-edge dust is dependent on ice-regolith temperature difference. • Sublimation flow is important to the generation of cap-edge dust.

Deliquescence probability maps of Mars and key limiting factors using GCM model calculations

There may be a chance of small-scale ephemeral liquid water formation on present day Mars, even though the current climate does not support the existence of larger bodies of water. Through a process called deliquescence, hygroscopic salts can enter solution by absorbing water vapor directly from the atmosphere. Due to the absence of in-situ deliquescence experiments so far, the most reliable way to forecast deliquescence is through atmospherical modeling, however, the locations and times when salty liquid water could emerge are not yet well known. In this paper we present our results of likely brine formation on Mars, their proposed locations and seasons, as well as the possible limiting factors. For our calculations we used the data of Laboratoire de M\'et\'eorologie Dynamique Mars General Circulation Model version 5. The results show that from L$_s$ 35$^\circ$ - L$_s$ 160$^\circ$, between 9 PM and 11 PM there is a good chance for calcium perchlorate deliquescence above 30$^\circ$ N, while in this zone the ideal regions are concentrated mostly to Acidalia Planitia and Utopia Planitia between 1 AM and 3 AM. We found that in the Southern Hemisphere, between L$_s$ 195$^\circ$ and L$_s$ 320$^\circ$, there is a noticeable, but weaker band in the vicinity of 60$^\circ$ S, and both Argyre Planitia and Hellas Planitia show some chance for brine formation. According to our statistics the key limiting factor of deliquescence could be relative humidity in most cases. Our results suggest that during summer -- early fall seasons, there could be deliquescence in both hemispheres in specific areas from the late evening until the early morning hours. There are only few studies detailing the geological and temporal distribution of brine formation through deliquescence, thus this work could be used as a good guide for future landing site analysis or in choosing a specific location for further research.

Thermal Tides in the Martian Atmosphere Near Northern Summer Solstice Observed by ACS/TIRVIM Onboard TGO

AbstractThermal tides in the Martian atmosphere are analyzed using temperature profiles retrieved from nadir observations obtained by the TIRVIM Fourier‐spectrometer, part of the Atmospheric Chemistry Suite onboard the ExoMars Trace Gas Orbiter. The data is selected near the northern summer solstice at solar longitude (LS) 75°–105° of Martian Year 35. The observations have a full local time coverage, which enables analyses of daily temperature anomalies. The observed zonal mean temperature is lower by 4–6 K at ∼100 Pa, but higher toward the summer pole, compared to the Laboratoire de Météorologie Dynamique (LMD) Mars General Circulation Model (GCM). Wave mode decomposition shows dominant diurnal tide and important semi‐diurnal tide and diurnal Kelvin wave, with maximal amplitudes of 5, 3, and 2.5 K, respectively, from tens to hundreds of Pa. The results generally agree well with the LMD Mars GCM, but with noticeable earlier phases of diurnal (∼1 hr) and semi‐diurnal (∼3 hr) tides.

Low‐Level Jets and the Convergence of Mars Data Assimilation Algorithms

AbstractData assimilation is an increasingly popular technique in Mars atmospheric science, but its effect on the mean states of the underlying atmosphere models has not been thoroughly examined. The robustness of results to the choice of model and assimilation algorithm also warrants further study. We investigate these issues using two Mars general circulation models (MGCMs), with particular emphasis on zonal wind and temperature fields. When temperature retrievals from the Mars Global Surveyor Thermal Emission Spectrometer (TES) are assimilated into the U.K.‐Laboratoire de Météorologie Dynamique MGCM to create the Mars Analysis Correction Data Assimilation (MACDA) reanalysis, low‐level zonal jets in the winter northern hemisphere shift equatorward and weaken relative to a free‐running control simulation from the same MGCM. The Ensemble Mars Atmosphere Reanalysis System (EMARS) reanalysis, which is also based on TES temperature retrievals, also shows jet weakening (but less if any shifting) relative to a control simulation performed with the underlying Geophysical Fluid Dynamics Laboratory MGCM. Examining higher levels of the atmosphere, monthly mean three‐dimensional temperature and zonal wind fields are in generally better agreement between the two reanalyses than between the two control simulations. In conjunction with information about the MGCMs' physical parameterizations, intercomparisons between the various reanalyses and control simulations suggest that overall the EMARS control run is plausibly less biased (relative to the true state of the Martian atmosphere) than the MACDA control run. Implications for future observational studies are discussed.

Simulation of Martian Dust Effects on Polar CO2 Ice Caps and Atmospheric Circulation Using the MarsWRF Model

AbstractMartian dust plays an important role in modulating climate. However, the effects of dust on polar CO2 ice caps, atmospheric circulation processes and the relationship between them are not yet clear. In this study, a Mars general circulation model (MarsWRF) was applied to investigate the impacts of the magnitude and timing of Martian dust storms on the spatiotemporal characteristics of polar CO2 ice caps and atmospheric circulation. The results show that dust can inhibit the sublimation of southern CO2 ice through the radiation effect. Under the “High Dust” scenario, the ice edge can extend up to 5° more equatorward than that under the “Standard” scenario around Ls = 220°. The extent of northern CO2 ice cap is hardly affected by dust because the impacts induced by dust mainly appear north of 80°N. By shifting the timing of maximum dust loading during the dust season, the "Early Dust" scenario inhibits the sublimation of the southern ice cap, while the "Late Dust" scenario accelerates the sublimation process. In addition, the variations in dust loading strength can lead to changes in three near‐surface wind belts, which are related to intensified Hardly circulation. The appearance of the warming vortex under the "Early Dust" scenario is delayed, and its intensity is 60 K lower than that observed in the "High Dust" and "Late Dust" scenarios. When dust loading increases, the northern CO2 condensation process in the Western Hemisphere accelerates, which is due to the increased pole‐to‐equator temperature gradient and the increased meridional wind speed.

ExoMars TGO/NOMAD‐UVIS Vertical Profiles of Ozone: 2. The High‐Altitude Layers of Atmospheric Ozone

AbstractSolar occultations performed by the Nadir and Occultation for MArs Discovery (NOMAD) ultraviolet and visible spectrometer (UVIS) onboard the ExoMars Trace Gas Orbiter (TGO) have provided a comprehensive mapping of atmospheric ozone density. The observations here extend over a full Mars year (MY) between April 21, 2018 at the beginning of the TGO science operations during late northern summer on Mars (MY 34, Ls = 163°) and March 9, 2020 (MY 35). UVIS provided transmittance spectra of the Martian atmosphere allowing measurements of the vertical distribution of ozone density using its Hartley absorption band (200–300 nm). The overall comparison to water vapor is found in the companion paper to this work (Patel et al., 2021, https://doi.org/10.1029/2021JE006837). Our findings indicate the presence of (a) a high‐altitude peak of ozone between 40 and 60 km in altitude over the north polar latitudes for at least 45% of the Martian year during midnorthern spring, late northern summer‐early southern spring, and late southern summer, and (b) a second, but more prominent, high‐altitude ozone peak in the south polar latitudes, lasting for at least 60% of the year including the southern autumn and winter seasons. When present, both high‐altitude peaks are observed in the sunrise and sunset occultations, suggesting that the layers could persist during the day. Results from the Mars general circulation models predict the general behavior of these peaks of ozone and are used in an attempt to further our understanding of the chemical processes controlling high‐altitude ozone on Mars.

Intense Zonal Wind in the Martian Mesosphere During the 2018 Planet‐Encircling Dust Event Observed by Ground‐Based Infrared Heterodyne Spectroscopy

AbstractWe report on the direct measurements of zonal winds around 80 km altitude during the 2018 planet‐encircling dust event (PEDE) by infrared (IR) heterodyne spectroscopy. The observed Doppler shifts assume intense retrograde (easterly) winds (208 ± 17 m s−1, 159 ± 20 m s−1, 211 ± 20 m s−1on June 21, June 27, August 31, 2018, respectively) in the equatorial region during the 2018 PEDE. This is significantly stronger than those during non‐storm conditions reported by the previous study (Sonnabend et al., 2012,https://doi.org/10.1016/j.icarus.2011.11.009). The substantial retrograde wind during the PEDE is qualitatively consistent with the predictions by the Mars general circulation models (MGCMs), however, the observed wind on 31, August, are of a larger magnitude. We evaluated the mechanism of acceleration using the output from a high‐resolution MGCM. We find out that the stronger winds are related to strengthening the meridional circulation across the equator and forcing by gravity waves.

Baroclinic waves in the northern hemisphere of Mars as observed by the MRO Mars Climate Sounder and the MGS Thermal Emission Spectrometer

The climatology of baroclinic waves in the northern hemisphere of Mars is investigated through analysis of observations by the infrared sounders on Mars Reconnaissance Orbiter (MRO) and Mars Global Surveyor (MGS). We focus on the lowest scale height above the surface, where the waves have a large impact on the Martian dust cycle. Profiles retrieved by the MRO Mars Climate Sounder (MCS) rarely reach the lower atmosphere at the season and location of interest. To fill this gap, we turn to observations in the MCS B1 channel (32 μm) when the instrument is viewing the surface. The signature of baroclinic waves appears in these data because of dust-related emission from the lower atmosphere and wave-induced variations of surface temperature. We supplement the MCS data with measurements of temperature at the 610-Pa pressure level from the MGS Thermal Emission Spectrometer (TES). Both data sets provide systematic coverage in latitude and longitude at two local times. Characteristics of baroclinic waves are derived through analysis of observations with a combined duration of about 8 Mars years. Basic results include least-squares solutions for wave amplitude and period at zonal wavenumber 1–3; the resolution is 4∘ in latitude and 14 solar days in time of observation. There is a strong similarity between the baroclinic waves observed by MCS and TES, which confirms the sensitivity of the MCS B1 channel to wave activity at pressures near 610 Pa. In all 8 Mars years, the baroclinic waves exhibit periodic transitions among modes with different zonal wavenumbers and a distinctive solstitial pause. Although the weather in each Mars year is unique in some respects, a composite of results from all years reveals a well-defined wave climatology. At each zonal wavenumber, large amplitudes are restricted to a pair of seasonal windows positioned symmetrically about the winter solstice. The wave-2 mode is strongest in early autumn and near the vernal equinox, whereas wave 3 is the dominant mode in mid-autumn and mid-winter, immediately before and after the solstitial pause. The interaction between baroclinic waves and dust storms is investigated through comparisons with spacecraft measurements of dust opacity. A strong wave-3 mode is often present during the initial growth phase of large, seasonal dust storms, which reflects the importance of wave-generated frontal dust storms in triggering these events. The wave-3 amplitude then decreases rapidly as the dust storm evolves; this occurs routinely in all Mars years considered here in connection with both mid-autumn “A” storms and mid-winter “C” storms. In some years A-storm suppression of the wave-3 mode marks the beginning of the solstitial pause. These results provide a basis for testing and development of Mars General Circulation Models as well as context for interpreting contemporaneous observations, such as spacecraft images of frontal and flushing dust storms.

Impact of Gravity Waves on the Middle Atmosphere of Mars: A Non‐Orographic Gravity Wave Parameterization Based on Global Climate Modeling and MCS Observations

AbstractThe impact of gravity waves (GW) on diurnal tides and the global circulation in the middle/upper atmosphere of Mars is investigated using a general circulation model (GCM). We have implemented a stochastic parameterization of non‐orographic GW into the Laboratoire de Météorologie Dynamique (LMD) Mars GCM (LMD‐MGCM) following an innovative approach. The source is assumed to be located above typical convective cells ( 250 Pa), and the effect of GW on the circulation and predicted thermal structure above 1 Pa ( 50 km) is analyzed. We focus on the comparison between model simulations and observations by the Mars Climate Sounder (MCS) on board Mars Reconnaissance Orbiter during Martian Year 29. MCS data provide the only systematic measurements of the Martian mesosphere up to 80 km to date. The primary effect of GW is to damp the thermal tides by reducing the diurnal oscillation of the meridional and zonal winds. The GW drag reaches magnitudes of the order of 1 m/s/sol above 10 Pa in the northern hemisphere winter solstice and produces major changes in the zonal wind field (from tens to hundreds of m/s), while the impact on the temperature field is relatively moderate (10–20 K). It suggests that GW‐induced alteration of the meridional flow is the main responsible for the simulated temperature variation. The results also show that with the GW scheme included, the maximum day‐night temperature difference due to the diurnal tide is around 10 K, and the peak of the tide is shifted toward lower altitudes, in better agreement with MCS observations.

Impact of surface Albedo on Martian photochemistry

Solar energy is the primary driving force behind a planet’s climate system, and surface albedo plays a key role in determining the energy budget of the planet. Coupling the Snow, Ice, and Aerosol Radiation (SNICAR) with the Laboratoire de Meteorologie Dynamique (LMD) Mars General Circulation Model (MGCM) to create a new coupled model leads to an approximately 4% drop in the net CO2 ice deposition on Mars. Newly simulated surface albedo affects the concentration of gaseous species in the Martian atmosphere (condensation-sublimation cycle). The new set-up also impacts the solar energy available in the atmosphere. These two effects together lead to subsequent and significant changes in other chemical species in the Martian atmosphere. Compared with results of the MGCM model alone, in the new coupled model CO2 (gas) and O3 show a drop of about 1.17% and 8.59% in their respective concentrations, while H2O (vapor) and CO show an increase of about 13.63% and 0.56% in their respective concentrations. Among trace species, OH shows a maximum increase of about 29.44%, while the maximum drop of 11.5% is observed in the O concentration. Photochemically neutral species such as Ar and N2 remain unaffected by the albedo changes.

Conceptual thermal design of a network of solar-powered Boardsat- and CubeSat-based landed spacecraft on Mars

In this paper, we assess the feasibility of the neoPASCAL thermal design by performing thermal analysis. NeoPASCAL is a network of compact solar-powered landers on Mars which aim to validate Mars General Circulation Models (GCMs) by measuring the diurnal variations in surface pressure. It is a modern revision of the original Pascal mission proposed in 1996, with each science station being ten times smaller in size and mass (a kg or less) by using miniaturised commercial off-the-shelf (COTS) electronic components and satellite platforms (i.e., Boardsat and CubeSat platforms). Despite the harsh thermal environments, the analysis shows that the Boardsat-based model can survive at ≤ ±60° latitude by using a large flexible-solar-cells-attached sail that was originally designed to attain soft landing. If successful, such a network would provide an unprecedented set of global meteorological data that can be used to investigate various meteorological phenomena including the general circulation.

Conceptual thermal design of a network of solar-powered Boardsat- and CubeSat-based landed spacecraft on Mars

In this paper, we assess the feasibility of the neoPASCAL thermal design by performing thermal analysis. NeoPASCAL is a network of compact solar-powered landers on Mars which aim to validate Mars General Circulation Models (GCMs) by measuring the diurnal variations in surface pressure. It is a modern revision of the original Pascal mission proposed in 1996, with each science station being ten times smaller in size and mass (a kg or less) by using miniaturised commercial off-the-shelf (COTS) electronic components and satellite platforms (i.e., Boardsat and CubeSat platforms). Despite the harsh thermal environments, the analysis shows that the Boardsat-based model can survive at ≤ ±60° latitude by using a large flexible-solar-cells-attached sail that was originally designed to attain soft landing. If successful, such a network would provide an unprecedented set of global meteorological data that can be used to investigate various meteorological phenomena including the general circulation.

Effects of the Mean Flow on Martian Transient Eddy Activity: Studies with an Idealized General Circulation Model

Abstract The extent to which the eddy statistics of the Martian atmosphere can be inferred from the mean state and highly simplified assumptions about diabatic and frictional processes is investigated using an idealized general circulation model (GCM) with Newtonian relaxation thermal forcing. An iterative technique, adapted from previous terrestrial studies, is used to generate radiative equilibrium temperatures such that the three-dimensional time-mean temperature fields of the idealized model match means computed from the Mars Analysis Correction Data Assimilation (MACDA). Focusing on a period of strong Northern Hemisphere eddy activity prior to winter solstice, it is found that the idealized model reproduces some key features of the spatial patterns of the MACDA eddy temperature variance and kinetic energy fields. The idealized model can also simulate aspects of MACDA’s seasonal cycle of spatial patterns of low-level eddy meridional wind and temperature variances. The most notable weakness of the model is its eddy amplitudes—both their absolute values and seasonal variations are quite unrealistic, for reasons unclear. The idealized model was also run with a mean flow based on output from the Geophysical Fluid Dynamics Laboratory (GFDL) full-physics Mars GCM. The idealized model captures the difference in mean flows between MACDA and the GFDL Mars GCM and reproduces a bias in the more complex model’s eddy zonal wavenumber distribution. This implies that the mean flow is an important influence on transient eddy wavenumbers and that improving the GFDL Mars GCM’s mean flow would make its eddy scales more realistic.