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We assimilate atmospheric temperatures from the Emirates Mars Infrared Spectrometer on board the Emirates Mars Mission (EMM) into the Mars Planetary Climate Model at the start of EMM's early science phase (Mars Year 36 Ls = 57.34–92.90°). Mars data assimilation benefits significantly from EMM's unique near‐hemispheric observations, frequent repeated observations of the same location, and full diurnal cycle coverage. Our analysis verifies well against in‐sample temperature observations, and is 1–3 K warmer than Mars Climate Sounder observations. We identify a warm front in concurrent Emirates eXploration Imager observations by correlating an elongated water ice cloud with temperatures and winds in the analysis; the analysis winds are consistent with its observed motion. We also calculate the full horizontal wind diurnal cycle; the zonal flow is weaker and the meridional circulation is stronger than simulating the same time period using the model alone. Plain Language Summary: The Emirates Mars Mission (EMM) promises advances in our understanding of Mars' atmosphere similar to when geostationary satellites first observed Earth. Data assimilation is a process where we combine observations with an atmospheric simulation. Using it to study Mars will benefit from EMM's observations of the whole of one side of the planet, frequent repeated observations of the same location, and observations of the full day‐night cycle. We combined observations of Mars atmospheric temperatures with our model over 79 Martian days at the start of EMM's main study period. We were able to demonstrate what is possible with EMM that has not been possible before. In particular, we found a long water ice cloud near the north pole in separate visible and ultraviolet images made by EMM. By comparing the motion and structure of this cloud with our results, we found that this "warm front" also appears in our results, and we were able to deduce properties of the front that were not observed. We were also able to deduce how Martian winds change over the course of the day and night, by making use of EMM's temperature observations over the full day‐night period. Key Points: We assimilate atmospheric temperature profiles from Emirates Mars Mission‐Emirates Mars InfraRed Spectrometer (EMM‐EMIRS) over a 79‐sol period in Mars Year 36 shortly before northern summer solsticeEMIRS' near‐hemispheric spatial coverage is used to analyze complete weather systems; we deduce the structure and motion of a warm frontThe horizontal wind diurnal cycle is retrieved by assimilation based on EMM‐EMIRS' extended local time coverage of atmospheric temperatures [ABSTRACT FROM AUTHOR]

The hydration of the martian regolith at decimeter depth scales varies regionally, suggestive of geologically sustained processes, independent of diurnal soil-atmosphere exchange. A combination of factors, including residual hydration from ancient processes in the hydrosphere/cryosphere, seasonal exchange between the crust and atmosphere in the martian critical zone, or structural water in minerals or salts sourced via hydrothermal processes can contribute to such lateral changes in bulk regolith hydration. Here, we consider the theoretical extent of regolith hydration from explosive volcanic eruptions and subsequent hydration. While magmatic degassing has previously been considered as a contributing factor to regolith hydration, the relationship between hydrated regolith and the depositional footprint of volcanic eruption columns and associated atmospheric dispersal remains poorly known. We run simulations of eruptions in an ancient atmosphere over a martian year to account for seasonality and produce theoretical ash deposition maps which are then input into a geographic weighted regression model to predict hydrated regolith. We find that ash deposited via explosive volcanism can help explain certain patterns of hydration enrichment in the martian regolith, including those near Apollinaris Patera Arabia Terra, and Sabea Terra. While the global patterns of regolith hydration cannot be explained by one process alone, we found that hydrated ash likely contributed to hydrated regolith at a commensurable level to other leading hydration mechanisms. The surface of Mars is blanketed by a pervasive layer of regolith, a mixture of unconsolidated sediment of multiple grainsizes that range from very fine dust to larger pebbles. This regolith contains significant amounts of water that are stored in the chemical bonds that make up the individual regolith grains. The amount of water bound in the regolith is spatially inconsistent throughout the planet; some areas contain more water, while others contain less. Several different geologic processes have likely contributed to these inconsistencies, including volcanic processes. While gentle volcanic outgassing has already been considered, here we specifically looked at how explosive volcanism and the associated spreading of volcanic ash in the martian atmosphere may have contributed to hydrated regolith patterns. By using multiple numerical simulations, we found that explosive volcanism likely contributed to certain patterns of hydration in the regolith along with other geologic processes. • There is a pathway between explosive volcanism and hydrated regolith. • Ancient explosive volcanism contributed to hydrated regolith patterns. • Areas near Apollinaris Patera, Arabia Terra, and Terra Sabaea show best fit between deposited ash and regolith hydration. [ABSTRACT FROM AUTHOR]

Our Global Circulation Model (GCM) simulates the atmospheric environment of Mars. It is developped at LMD (Laboratoire de Meteorologie Dynamique, Paris, France) in close collaboration with several teams in Europe (LATMOS, France, University of Oxford, The Open University, the Instituto de Astrofisica de Andalucia), and with the support of ESA (European Space Agency) and CNES (French Space Agency). GCM outputs are compiled to build a Mars Climate Database, a freely available tool useful for the scientific and engineering communities. The Mars Climate Database (MCD) has over the years been distributed to more than 350 teams around the world. The latest series of reference simulations have been compiled in version 5.3 of the MCD which was released in 2017.To summarize, MCD v5.3 provides:- Climatologies over a series of synthetic dust scenarios: standard (climatology) year, cold (ie: low dust), warm (ie: dusty atmosphere) and dust storm, all topped by various cases of Extreme UV solar inputs (low, mean or maximum). These scenarios have been derived from home-made, instrument-derived (TES, THEMIS, MCS, MERs), dust climatology of the last 8 Martian years. The MCD also provides simulation outputs (MY24-33) representative of these actual years.- Mean values and statistics of main meteorological variables (atmospheric temperature, density, pressure and winds), as well as surface pressure and temperature, CO2 ice cover, thermal and solar radiative fluxes, dust column opacity and mixing ratio, [H20] vapor and ice columns, concentrations of many species: [CO], [O2], [O], [N2], [H2], [O3],...- A high resolution mode which combines high resolution (32 pixel/degree) MOLA topography records and Viking Lander 1 pressure records with raw lower resolution GCM results to yield, within the restriction of the procedure, high resolution values of atmospheric variables.- The possibility to reconstruct realistic conditions by combining the provided climatology with additional large scale and small scale perturbations schemes.At EGU, we will report on the latest improvements in the Mars Climate Database, with comparisons with available measurements from orbit (e.g.: TES, MCS, TGO) and landers (Viking, Phoenix, Curiosity). [ABSTRACT FROM AUTHOR]

Recent simulations of the Institut Pierre-Simon Laplace (IPSL) Venus Global Climate Model (VGCM) developed at the Laboratoire de Météorologie Dynamique (LMD) were performed with a model top raised from ∼10−5 (∼150 km) to ∼10−8 Pa (180–250 km; upper boundary). The parameterizations of non-LTE CO 2 near infrared heating rates and of non-orographic gravity waves were improved. In addition, a tuning of atomic oxygen production was introduced to improve related effects (heating and cooling) and resulting thermospheric number densities. This work focusses on validating the modelled thermospheric structure using data from the Pioneer Venus, Magellan and Venus Express missions which cover similar and complementary (equator and pole) regions at different periods of solar activity, typically above altitudes of 130 km. This version of the IPSL VGCM shows good agreement with the diurnal evolution of the exospheric temperature at the equator reconstructed from the atomic oxygen scale height of the Pioneer Venus Orbiter Neutral Mass Spectrometer data. The model is also able to reproduce the sensitivity of the exospheric temperature and species density to the EUV flux of the solar high activity period (from 180 to 230 solar flux unit; s.f.u). However, to fit with the PV-ONMS density observations, it was necessary to increase the photodissociation of CO 2 into CO and O above 135 km by a factor of 10. Indeed, our study points to the importance of an additional source of oxygen and carbon monoxide production above 130 km other than CO 2 photolysis to explain the vertical profiles of CO and O number density in the thermosphere. Moreover, the presence of a GW drag at altitudes above 140 km has a significant impact on the nightside temperature value and its distribution. [ABSTRACT FROM AUTHOR]

Observations by the Emirates eXploration Imager (EXI) on‐board the Emirates Mars Mission are used to characterize the diurnal, seasonal, and spatial behavior of aphelion cloud belt during Mars Year 36 LS ∼ 30°–190°. Building from previous work with the Mars Color Imager (MARCI) onboard the Mars Reconnaissance Orbiter, we retrieve water ice extinction optical depth (τice) with an uncertainty ±0.0232 (excluding particle size effects). We connect EXI and MARCI using radiance and τice. Zonal and meridional diurnal trends are analyzed over 6–18 hr Local True Solar Time. The retrievals show large morning‐evening asymmetries about a minimum near 12 hr. The latitudinal distributions in early morning are extensive and particularly striking near mid‐summer. Comparisons to the Mars Planetary Climate Model show reasonable agreement with basic diurnal behavior, but noticeable departures include too much water ice in early morning, the general latitudinal extent, and behavior at smaller scales like the volcanoes and other topographically distinct features. Plain Language Summary: Water ice clouds have important roles in the Martian atmosphere because they can influence weather and act as probes of important weather and climate processes. Using the camera on‐board the Emirates Mars Mission, water ice clouds are studied for the first time throughout the Martian day and year at scales of 10–20 km around the planet. We study a key cloud structure called the aphelion cloud belt (ACB) that encircles the planet at low latitudes during the northern hemisphere spring and summer seasons. Using the camera images from this period, we examine how the ACB structure changes from morning through evening and throughout these two seasons. We developed a computer program that converts the brightness of a pixel into a measure of the cloud thickness. We find that the ACB clouds are much thicker and wide‐spread in the early morning compared to other times of day; and are much more extant across the planet in the morning, particularly in mid‐summer. We also compare to weather prediction programs and find important differences that will help scientists improve Mars weather forecasts for future research and missions. Key Points: The Emirates eXploration Imager is used to retrieve ice extinction optical depth in Mars Year 36 during solar longitudes 30–190°Diurnal trends of the aphelion cloud belt are examined between 6 and 18 hr using both zonal and meridional maps, revealing new behaviorComparisons to the Mars Planetary Climate Model show reasonable agreement with broad structure, but important differences are noted [ABSTRACT FROM AUTHOR]

Temperature profiles retrieved using the first set of data of the Emirates Mars InfraRed Spectrometer obtained during the science phase of the Emirates Mars Mission are used for the analysis of migrating thermal tides in the Martian atmosphere. The selected data cover a solar longitude (LS) range of 60°–90° of Martian Year 36. The novel orbit design of the Hope Probe leads to a good geographic and local time coverage that significantly improves the analysis. Wave mode decomposition suggests dominant diurnal tide and important semi‐diurnal tide with maximal amplitudes of 6 and 2 K, respectively, as well as the existence of ∼0.5 K ter‐diurnal tide. The results agree well with predictions by the Mars Planetary Climate Model, but the observed diurnal tide has an earlier phase (3 hr), and the semi‐diurnal tide has an unexpectedly large wavelength (∼200 km). Plain Language Summary: As a result of its small thickness, the Martian atmosphere experiences large temperature variations within each Martian day due to the incoming sunlight. Such rapid and large temperature variations excite waves propagating in the Martian atmosphere that highly influence winds, cloud formation, and dust transport. In this work, we use the atmospheric temperature measurements derived using observations obtained by an infrared spectrometer onboard the Hope Probe to analyze the diurnal temperature variations and the excited waves. The novel design of the spacecraft's orbit provides good data coverage in location and time, leading to the success of detailed analyses of the waves that propagate in the Martian atmosphere synchronously with the movement of the Sun, among which a new wave mode with a period of one third of a Martian day is detected. We compare the results with predictions provided by numerical simulations, and they show good agreements in the wave strengths, but the observed waves have different wavelengths and phases. Key Points: Migrating thermal tides in the Martian atmosphere are analyzed using the first set of Emirates Mars Mission/Emirates Mars InfraRed Spectrometer observationsThe observed amplitudes of diurnal and semi‐diurnal tides agree well with model predictions, but with different phases and wavelengthsTer‐diurnal tide is detected with an amplitude of ∼0.5 K, due to the observations covering the full range of local times [ABSTRACT FROM AUTHOR]

Thermal 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. Plain Language Summary: Unlike the Earth, daily temperature variation on Mars is as large as tens of degrees because of its thin atmosphere. The sunlight absorbed by the Martian surface and dust in the atmosphere leads to dramatic temperature increase in the lower atmosphere during daytime. Such large and regular changes can trigger temperature waves, and some modes of them can propagate into higher altitudes, where they become the major factor controlling the daily temperature variation. In this work, temperature profiles obtained using thermal‐infrared spectra are analyzed. Zonal mean temperature is compared with numerical simulations of the Martian atmosphere. Different types of the wave modes are computed through decomposition. Results from the observation agree well with model prediction when the observation mechanisms are taken into consideration. Estimation of the strength of these waves can be improved in the future with improved design of observation strategies. Key Points: Thermal tides in the Martian atmosphere are investigated using temperature profiles retrieved from TIRVIM nadir observationsDiurnal tide dominates daily temperature variations; semi‐diurnal tide and diurnal Kelvin wave are also importantObservations agree well with numerical simulations, but suggest phases of diurnal and semi‐diurnal tides earlier than predicted [ABSTRACT FROM AUTHOR]

The deuterium to hydrogen (D/H) ratio is commonly used to investigate the history of water on Mars, yet the mechanisms controlling present‐day HDO behavior are poorly understood. Significant variations of the D/H ratio were first predicted on the basis of a 3D global climate model, which were later confirmed by ground‐based observations. This behavior, consisting of lower HDO/H2O ratios in the colder regions of Mars, is related to the isotopic fractionation occurring at condensation. We leverage this previous effort and present an updated implementation, using the modern version of the model, that remains in agreement with the older version. We explore the impact of the global dust storm (GDS) that occurred during Martian year 34 (MY34) on HDO. Our simulations indicate that HDO is on average 40% more abundant at 100 km during the MY34 GDS year than during a regular year, with likely large consequences for the escape flux of water that year. Plain Language Summary: HDO, the semi‐heavy isotope of water, when compared to water, is a good indicator of how much water has been escaping from the atmosphere of Mars over the ages. Ultimately, it can be used to estimate the past reservoir of water available on Mars in its early youth. Because HDO has a slightly higher molecular mass compared to H2O, condensation induces an enrichment of HDO in the ice phase compared with the vapor phase. This subsequently causes spatial and temporal variations of the deuterium to hydrogen ratio. We use a global circulation model to simulate the HDO cycle in the atmosphere. Our model is an upgrade of the previous model presented in Montmessin et al. (2005, Journal of Geophysical Research, 110(E3), E10004. doi:10.1029/2004JE002357). We then simulate the effect of the global dust storm that affected Mars during the summer of 2018, and show that it should have had a strong impact on the vertical distribution of HDO, allowing it to reach higher altitudes. Such simulations are intended to be compared with observations from the Trace Gas Orbiter, currently in orbit around Mars. Key Points: We reimplemented the HDO cycle in a more recent version of the Laboratoire de Météorologie Dynamique Mars global climate modelWe reproduce the observed gradient of the deuterium to hydrogen ratio between cold and warm regionsThe global dust storm of Martian year 34 has a strong effect on the vertical distribution of HDO [ABSTRACT FROM AUTHOR]

The cloud parameterizations of the LMDZ6A climate model (the atmospheric component of the IPSL‐CM6 Earth system model) are entirely described, and the global cloud distribution and cloud radiative effects are evaluated against the CALIPSO‐CloudSat and CERES observations. The cloud parameterizations in recent versions of LMDZ favor an object‐oriented approach for convection, with two distinct parameterizations for shallow and deep convection and a coupling between convection and cloud description through the specification of the subgrid‐scale distribution of water. Compared to the previous version of the model (LMDZ5A), LMDZ6A better represents the low‐level cloud distribution in the tropical belt, and low‐level cloud reflectance and cover are closer to the PARASOL and CALIPSO‐GOCCP observations. Mid‐level clouds, which were mostly missing in LMDZ5A, are now better represented globally. The distribution of cloud liquid and ice in mixed‐phase clouds is also in better agreement with the observations. Among identified deficiencies, low‐level cloud covers are too high in mid‐latitude to high‐latitude regions, and high‐level cloud covers are biased low globally. However, the cloud global distribution is significantly improved, and progress has been made in the tuning of the model, resulting in a radiative balance in close agreement with the CERES observations. Improved tuning also revealed structural biases in LMDZ6A, which are currently being addressed through a series of new physical and radiative parameterizations for the next version of LMDZ. Plain Language Summary: This paper describes the representation of clouds in the latest version of LMDZ, which is a French atmospheric model used for climate change projections. Along with other international climate models, it serves as a basis for the IPCC (Intergovernmental Panel on Climate Change) report by contributing to the CMIP project (Climate Model Intercomparison Project). Clouds are especially important in the climate system because they reflect a lot of sunlight and also absorb and emit a lot of infrared radiation. They can either amplify or reduce the current global warming depending on their change in opacity, altitude, and detailed properties. It is therefore essential to represent them accurately in climate models. The main physical equations used to compute cloud properties in LMDZ are introduced, and the model results are compared to various satellite observations. It reveals that low‐level and mid‐level clouds are in better agreement with the observations than before but that high‐level clouds remain difficult to simulate realistically. Ongoing developments aimed at solving these remaining deficiencies are finally described. Key Points: Cloud parameterizations of the LMDZ6A climate model are entirely describedLow‐level and mid‐level cloud distribution and radiative effects are improved compared to LMDZ5ALMDZ6A is better tuned than LMDZ5A, and knowledge of its structural deficiencies has been gained [ABSTRACT FROM AUTHOR]

The Cassini mission unveiled the intense and diverse activity in Saturn's atmosphere: banded jets, waves, vortices, equatorial oscillations. To set the path towards a better understanding of those phenomena, we performed high-resolution multi-annual numerical simulations of Saturn's atmospheric dynamics. We built a new Global Climate Model [GCM] for Saturn, named the Saturn DYNAMICO GCM, by combining a radiative-seasonal model tailored for Saturn to a hydrodynamical solver based on an icosahedral grid suitable for massively-parallel architectures. The impact of numerical dissipation, and the conservation of angular momentum, are examined in the model before a reference simulation employing the Saturn DYNAMICO GCM with a 1/2° latitude-longitude resolution is considered for analysis. Mid-latitude banded jets showing similarity with observations are reproduced by our model. Those jets are accelerated and maintained by eddy momentum transfers to the mean flow, with the magnitude of momentum fluxes compliant with the observed values. The eddy activity is not regularly distributed with time, but appears as bursts; both barotropic and baroclinic instabilities could play a role in the eddy activity. The steady-state latitude of occurrence of jets is controlled by poleward migration during the spin-up of our model. At the equator, a weakly-superrotating tropospheric jet and vertically-stacked alternating stratospheric jets are obtained in our GCM simulations. The model produces Yanai (Rossby-gravity), Rossby and Kelvin waves at the equator, as well as extratropical Rossby waves, and large-scale vortices in polar regions. Challenges remain to reproduce Saturn's powerful superrotating jet and hexagon-shaped circumpolar jet in the troposphere, and downward-propagating equatorial oscillation in the stratosphere. • A new Global Climate Model for Saturn with radiative transfer • High-resolution numerical simulations on a duration of 15 Saturn years • Results on zonal jets, waves, eddies in Saturn's troposphere [ABSTRACT FROM AUTHOR]

This study presents the version of the LMDZ global atmospheric model used as the atmospheric component of the Institut Pierre Simon Laplace coupled model (IPSL‐CM6A‐LR) to contribute to the 6th phase of the international Coupled Model Intercomparison Project (CMIP6). This LMDZ6A version includes original convective parameterizations that define the LMDZ "New Physics": a mass flux parameterization of the organized structures of the convective boundary layer, the "thermal plume model," and a parameterization of the cold pools created by reevaporation of convective rainfall. The vertical velocity associated with thermal plumes and gust fronts of cold pools are used to control the triggering and intensity of deep convection. Because of several shortcomings, the early version 5B of this New Physics was worse than the previous "Standard Physics" version 5A regarding several classical climate metrics. To overcome these deficiencies, version 6A includes new developments: a stochastic triggering of deep convection, a modification of the thermal plume model that allows the representation of stratocumulus and cumulus clouds in a unified framework, an improved parameterization of very stable boundary layers, and the modification of the gravity waves scheme targeting the quasi‐biennal oscillation in the stratosphere. These improvements to the physical content and a more well‐defined tuning strategy led to major improvements in the LMDZ6A version model climatology. Beyond the presentation of this particular model version and documentation of its climatology, the present paper underlines possible methodological pathways toward model improvement that can be shared across modeling groups. Plain Language Summary: The improvement of global numerical models is essential for the anticipation of future climate changes. We present significant advances in the physical content of a particular atmospheric model which contributes to the simulations of the Coupled Model Intercomparison project CMIP that feed reports from the IPCC. We document in particular the improvements of the representation through "parameterizations" of convective and cloudy processes. The article emphasizes the importance of strengthening the formalization of the methodology of development and tuning of models, so that new physical ideas can be translated into effective improvement of the climate representation. Key Points: The development strategy of the LMDZ6A global atmospheric circulation model is presentedImprovements with respect to previous versions are documented in the context of the Coupled Model Intercomparison Project, CMIPThe improvements are based on significant changes of the physics content as well as on a better controlled tuning strategy [ABSTRACT FROM AUTHOR]

The loss of water from Mars to space is thought to result from the transport of water to the upper atmosphere, where it is dissociated to hydrogen and escapes the planet. Recent observations have suggested large, rapid seasonal intrusions of water into the upper atmosphere, boosting the hydrogen abundance. We use the Atmospheric Chemistry Suite on the ExoMars Trace Gas Orbiter to characterize the water distribution by altitude. Water profiles during the 2018–2019 southern spring and summer stormy seasons show that high-altitude water is preferentially supplied close to perihelion, and supersaturation occurs even when clouds are present. This implies that the potential for water to escape from Mars is higher than previously thought. [ABSTRACT FROM AUTHOR]

Highlights • We examine the record of atmospheric pressure in Gale crater measured in-situ by the REMS and compare the data with pressure predictions from the Mars Climate Database (MCD). • Seasonal and daily trends in pressure data from REMS are well reproduced by MCD. • Differences between the MCD pressure data and the REMS measurements are produced by meteorological features that are identified on particular groups of sols. • We show that regional dust storms and dust abundance at the crater are important factors in the behaviour of the pressure causing most of the largest REMS-MCD differences. Abstract We examine the record of atmospheric pressure in Gale crater measured in-situ by the Rover Environmental Monitoring Station (REMS) instrument (Gómez-Elvira et al., 2012) on the Mars Science Laboratory (MSL) rover over two Martian years. We compare the data with pressure predictions from the Mars Climate Database (MCD) (Forget et al., 1999; Millour et al., 2015) version 5.2, which is a climatological database derived from numerical simulations of the Martian atmosphere produced by a General Circulation Model run over several Martian years. Seasonal and daily trends in pressure data from REMS are well reproduced by the standard climatology of the MCD using its high resolution mode. This high-resolution mode extrapolates pressure values from the nominal model into the altitude of each location using a high-resolution topography model and a fine tuning of the vertical scale height that was chosen to mimic effects of slope winds not directly accounted for in the General Circulation Model on which the MCD is based. Differences between the synthetic MCD pressure data and the REMS measurements are produced by meteorological features that are identified on particular groups of sols and quantified in intensity. We show that regional dust storms outside Gale crater and dust abundance at the crater are important factors in the behaviour of the pressure exciting larger amplitudes on the daily pressure variations and causing most of the largest REMS-MCD differences. We compare the pressure signals with published data of the dust optical depth obtained by the REMS ultraviolet photodiodes and the Mastcam instrument on MSL, and with orbital images of the planet acquired by the MARCI instrument on the Mars Reconnaissance Orbiter (MRO). We show that in some cases regional dust storms induce a characteristic signature in the surface pressure measured by REMS several sols before the dust arrives to Gale crater. We explore the capability of daily pressure measurements to serve as a fast detector of the development of dust storms in the context of the MSL, Insight and Mars 2020 missions. [ABSTRACT FROM AUTHOR]

Global climate modeling of the Mars water cycle is usually performed at relatively coarse resolution ( 200 − 300 km ), which may not be sufficient to properly represent the impact of waves, fronts, topography effects on the detailed structure of clouds and surface ice deposits. Here, we present new numerical simulations of the annual water cycle performed at a resolution of 1° × 1° (∼ 60 km in latitude). The model includes the radiative effects of clouds, whose influence on the thermal structure and atmospheric dynamics is significant, thus we also examine simulations with inactive clouds to distinguish the direct impact of resolution on circulation and winds from the indirect impact of resolution via water ice clouds. To first order, we find that the high resolution does not dramatically change the behavior of the system, and that simulations performed at ∼ 200 km resolution capture well the behavior of the simulated water cycle and Mars climate. Nevertheless, a detailed comparison between high and low resolution simulations, with reference to observations, reveal several significant changes that impact our understanding of the water cycle active today on Mars. The key northern cap edge dynamics are affected by an increase in baroclinic wave strength, with a complication of northern summer dynamics. South polar frost deposition is modified, with a westward longitudinal shift, since southern dynamics are also influenced. Baroclinic wave mode transitions are observed. New transient phenomena appear, like spiral and streak clouds, already documented in the observations. Atmospheric circulation cells in the polar region exhibit a large variability and are fine structured, with slope winds. Most modeled phenomena affected by high resolution give a picture of a more turbulent planet, inducing further variability. This is challenging for long-period climate studies. [ABSTRACT FROM AUTHOR]

Large-Eddy Simulations (LES) for Mars resolve the Planetary Boundary Layer (PBL) turbulent dynamics by using a very fine horizontal resolution of a few tens of meters. LES modeling is becoming a more and more useful tool to prepare the robotic exploration of Mars by providing means to evaluate the intensity of convective plumes and vortices, horizontal wind gustiness, and turbulent fluctuations of temperature in the Martian PBL. In such context, and given the relative paucity of turbulence-related measurements on Mars, an intercomparison of LES models is a fruitful way to evaluate the models' predictions and to indicate possible areas of improvement. Thus, to prepare the landing of the ExoMars Schiaparelli lander (also named ExoMars Demonstrator Module, EDM), scheduled for October 2016, the results of the Laboratoire de Météorologie Dynamique (LMD) and South-West Research Institute (SwRI) LES models have been compared. The objective of this study is to determine the range of uncertainties, and dispersions, of the two numerical models' predictions, for the critical phase of the spacecraft's descent in the Martian daytime turbulent PBL. First, a strategy is defined to ensure similar radiative forcing in both the LMD and SwRI models. Then, LES are performed over a flat terrain with and without large-scale ambient horizontal wind. The LMD and SwRI Martian LES models predict similar temporal evolution of the PBL and organization in the horizontal and vertical wind fields. However, the convective motions in the daytime PBL are more vigorous by a factor 1.5-2 in SwRI results than in LMD results, independently of the presence or not of ambient horizontal wind. This discrepancy is further investigated through sensitivity studies to surface conditions, ambient wind, and airborne dust loading. [ABSTRACT FROM AUTHOR]

The degradation in electrical output of solar arrays on Mars landers and rovers is reviewed. A loss of 0.2% per Sol is typical, although observed rates of decrease in 'dust factor' vary between 0.05% and 2% per Sol. 0.2%/Sol has been observed throughout the first 800 Sols of the ongoing InSight mission, as well as the shorter Mars Pathfinder and Phoenix missions. This rate was also evident for much of the Spirit and Opportunity missions, but the degradation there was episodically reversed by cleaning events due to dust devils and gusts. The enduring success of those rover missions may have given an impression of the long-term viability of solar power on the Martian surface that is not globally-applicable: the occurrence of cleaning events with an operationally-useful frequency seems contingent upon local meteorological circumstances. The conditions for significant cleaning events have apparently not been realized at the InSight landing site, where, notably, dust devils have not been detected in imaging. Optical obscuration by dust deposition and removal has also been observed by ultraviolet sensors on Curiosity, with a similar (but slightly higher) degradation rate. The observations are compared with global circulation model (GCM) results: these predict a geographically somewhat uniform dust deposition rate, while there is some indication that the locations where cleaning events were more frequent may be associated with weaker background winds and a deeper planetary boundary layer. The conventional Dust Devil Activity metric in GCMs does not effectively predict the different dust histories. • Presents solar array dust factor evolution for 6 landed missions. • Evaluates statistics of solar array output decline, typically 0.2%/Sol but ranging 0.05–2%/Sol. • Determines statistics of cleaning events. • Compares evolution with meteorological predictions at the different landing sites. [ABSTRACT FROM AUTHOR]

Abstract: Radiative control of surface temperature is a key characteristic of the martian environment and its low-density atmosphere. Here we show through meteorological modeling that surface temperature can be far from radiative equilibrium over numerous sloping terrains on Mars, where nighttime mesoscale katabatic winds impact the surface energy budget. Katabatic circulations induce both adiabatic atmospheric heating and enhancement of downward sensible heat flux, which then becomes comparable to radiative flux and acts to warm the ground. Through this mechanism, surface temperature can increase up to 20K. One consequence is that warm signatures of surface temperature over slopes, observed through infrared spectrometry, cannot be systematically associated with contrasts of intrinsic soil thermal inertia. Apparent thermal inertia maps retrieved thus far possibly contain wind-induced structures. Another consequence is that surface temperature observations close to sloping terrains could allow the validation of model predictions for martian katabatic winds, provided contrasts in intrinsic thermal inertia can be ruled out. The thermal impact of winds is mostly discussed in this paper in the particular cases of Olympus Mons/Lycus Sulci and Terra Meridiani but is generally significant over any sloped terrains in low thermal inertia areas. It is even general enough to apply under daytime conditions, thereby providing a possible explanation for observed afternoon surface cooling, and to ice-covered terrains, thereby providing new insights on how winds could have shaped the present surface of Mars. [Copyright &y& Elsevier]

The Composite InfraRed Spectrometer (CIRS) on board Cassini revealed an equatorial oscillation of stratospheric temperature, reminiscent of the Earth's Quasi-Biennial Oscillation (QBO), as well as anomalously high temperatures under Saturn's rings. To better understand these predominant features of Saturn's atmospheric circulation in the stratosphere, we have extended to the upper stratosphere the DYNAMICO-Saturn global climate model (GCM), already used in a previous publication to study the tropospheric dynamics, jets formation and planetary-scale waves activity. Firstly, we study the higher model top impact on the tropospheric zonal jets and kinetic energy distribution. Raising the model top prevents energy and enstrophy accumulation at tropopause levels. The reference GCM simulation with 1/2°latitude/longitude resolution and a raised model top exhibits a QBO-like oscillation produced by resolved planetary-scale waves. However, the period is more irregular and the downward propagation faster than observations. Furthermore, compared to the CIRS temperature retrievals, the modeled QBO-like oscillation underestimates by half both the amplitude of temperature anomalies at the equator and the vertical characteristic length of this equatorial oscillation. This QBO-like oscillation is mainly driven by westward-propagating waves; a significant lack of eastward wave-forcing explains a fluctuating eastward phase of the QBO-like oscillation. We also show that the seasonal cycle of Saturn is a key parameter of the establishment and the regularity of the equatorial oscillation. At 20 ∘ N and 20 ∘ S latitudes, the DYNAMICO-Saturn GCM exhibits several strong seasonal eastward jets, alternatively in the northern and southern hemisphere. These jets are correlated with the rings' shadowing. Using a GCM simulation without rings' shadowing, we show its impact on Saturn's stratospheric dynamics. Both residual-mean circulation and eddy forcing are impacted by rings' shadowing. In particular, the QBO-like oscillation is weakened by an increased drag caused by those two changes associated with rings' shadowing. • A troposphere-to-stratosphere Global Climate Model for Saturn is presented. • The simulated stratospheric equatorial oscillation is more irregular in period and the associated temperature anomalies are underestimated by 10 K in amplitude compared to observation. • Saturn's ring shadowing impacts the stratospheric equatorial dynamics, the equatorial oscillation periodicity and equatorial winds intensity. [ABSTRACT FROM AUTHOR]

A Martian water-ice cloud climatology has been extracted from OMEGA data covering 7 Martian years (MY 26–32) on the dayside. We derived two products, the Reversed Ice Cloud Index (ICIR) and the Percentage of Cloudy Pixels (PCP), indicating the mean cloud thickness and nebulosity over a regular grid (1° longitude × 1° latitude × 1° Ls × 1 h Local Time). The ICIR has been shown to be a proxy of the water-ice column derived from the Mars Climate Database. The PCP confirms the existence and location of the main cloud structures mapped with the ICIR, but also gives a more accurate image of the cloud cover. We observed a more dense cloud coverage over Hellas Planitia, the Lunae Planum region and over large volcanoes (Tharsis volcanoes, Olympus and Elysium Montes) in the aphelion belt. For the first time, thanks to the fact that Mars Express is not in Sun-synchronous orbit, we can explore the clouds diurnal cycle at a given season by combining the seven years of observations. However, because of the eccentric orbit, the temporal coverage remains limited. Identified limitations of the dataset are its small size, the difficult distinction between ice clouds and frosts, and the impact of surface albedo on data uncertainty. We could nevertheless study the diurnal cloud life cycle by averaging the data over larger regions: from specific topographic features (covering a few degrees in longitude and latitude) up to large climatic bands (covering all longitudes). We found that in the tropics (25°S – 25°N) around northern summer solstice, the diurnal thermal tide modulates the abundance of clouds, which is reduced around noon (Local Time). At northern midlatitudes (35°N – 55°N), clouds corresponding to the edge of the north polar hood are observed mainly in the morning and around noon during northern winter (Ls = 260° – 30°). Over Chryse Planitia, low lying morning fogs dissipate earlier and earlier in the afternoon during northern winter. Over Argyre, clouds are present over all daytime during two periods, around Ls = 30° and 160°. • First daytime water-ice cloud climatology covering the Martian day and year. • 10 years of OMEGA observations unveil the Martian water-ice cloud life cycle. [ABSTRACT FROM AUTHOR]

We report a new water‐ice cloud feature observed during the Mars year 34 global dust storm: twilight cloud bands that routinely formed just past the evening terminator. We use images taken by the MAVEN/IUVS instrument. These bands were often latitudinally continuous, spanning over 6,000 km and were present between 18:00 and 19:00 local time. They were present for nearly the entire time IUVS imaged the evening terminator and often reached altitudes of at least 40 to 50 km during the mature phase of the storm. We compare these observations to LMD global climate model simulations. The simulations generally contain the temporal and spatial extents of the bands seen in IUVS data throughout the storm, but there are some discrepancies. We infer that these clouds formed as a result of semidiurnal thermal tides. Plain Language Summary: Water‐ice clouds and dust are among the most common particles in the Martian atmosphere, but the effect of global dust storms on cloud formation is largely unknown. We observed cloud bands that repeatedly formed near dusk during the Mars year 34 global dust storm. We saw these bands throughout the storm at locations all across the planet. We investigate this feature by using a global climate model, which predicted the formation of these cloud bands as a result of rapidly changing temperatures. The simulations of the bands contain several features seen in our observations, but not all. Key Points: We observed a new cloud formation phenomenon just after sunset during the Mars year 34 global dust storm in MAVEN/IUVS imagesGlobal climate model simulations are able to reproduce several but not all aspects of our observationsThese twilight clouds formed due to semidiurnal thermal tides [ABSTRACT FROM AUTHOR]

The InSight spacecraft landed in the flat regions of Elysium Planitia on November 26th 2018. The instruments on board InSight make it capable of acting as a meteorological station at the surface of Mars. A pressure sensor (PS), two temperature and wind sensor booms (TWINS), along with the InSight FluxGate (IFG) magnetometer, form the Auxiliary Sensor Payload Suite (APSS). This is complemented by capabilities to measure surface brightness temperature by the radiometer in the Heat-Flow and Physical Properties Package (HP3) suite, to explore the impact of atmospheric processes on seismic measurements by SEIS, and to use InSight cameras to estimate atmospheric opacity (notably caused by suspended dust particles) and other atmospheric phenomena such as clouds and dust devils. We will discuss results drawn from atmospheric measurements on board InSight over the first two months of operation, highlighting new perspectives permitted by the high-frequency, continuous nature of the InSight acquisitions. Surface pressure measurements record global-to-local atmospheric phenomena: CO2 condensation (annual), dust cycle and storms (seasonal), baroclinic waves (weekly), thermal tides (daily), gravity waves (thousands of seconds), convective cells (hundreds of seconds), convective vortices (tens of seconds, leading to dust devils if dust particles are transported in the vortex). Two main large-scale wind regimes were expected from Global Climate Modeling at the InSight landing site during a typical year: towards the northwest in northern spring and summer, then in the opposite direction in southern summer. Existing in-situ measurements on Mars and Large-Eddy Simulations indicate that daytime convective vortices and cells not only impact pressure, but also temperature and winds; the nighttime atmosphere on Mars is comparatively much less turbulent and dominated by shear-driven turbulence, in contrast to the buoyancy-driven turbulence active in daytime. All such existing measurements and model predictions will be compared and challenged with InSight measurements. Seismic signatures associated with atmospheric phenomena will also be discussed, with a particular emphasis on the knowledge gained by the unprecedented measurements performed by InSight's seismometers. [ABSTRACT FROM AUTHOR]

NASA's InSight mission landed in Elysium Planitia (~4.5ºN, 136ºE) on November 2018 at Ls ~298°. It carries, among other instruments, the APSS (Auxiliary Payload Sensor Suite) that includes the TWINS (Temperature and Winds Sensor) package [1, 2], heritage from the previous sensors sent to Mars as part of the Mars Science Laboratory (MSL). This will allow surface wind patterns to be measured at InSight's landing site, and - given its proximity to MSL's location in Gale Crater - will complement the diurnal and seasonal wind characterization already performed using data from MSL's Rover Environmental Monitoring Station (REMS) wind sensor [3, 4]. The latter is of particular interest given the damage the REMS wind sensor suffered during MSL's landing, resulting in little reliable wind data available for the northern winter season, which prevents a full understanding of the seasonal wind patterns in Gale Crater, and especially of the interaction between local, regional and large-scale circulations.A large set of wind data have already been obtained from the InSight wind sensor, enabling the diurnal cycle of wind speed and direction in local winter to be determined for the landing site in Elysium Planitia. The wind patterns are expected to show significant sol-to-sol variability and a complex diurnal cycle, although not as complex as seen in Gale Crater [3,4]. The observed wind patterns are dominated by the large-scale Hadley circulation in this season, but also affected by the regional upslope and downslope winds, which shape the diurnal behavior [1]. Comparisons of InSight data with data acquired at the MSL site aid in interpreting how the large-scale, regional and local circulations interact to lead to the diurnal cycle of winds observed at each site, also improving circulation model predictions for both regions. A complementary work related to a detailed description of how using data from different sources, such as MSL and Insight, help to constrain models of the more general region, will be presented in [5].[1] Spiga, A. et al. (2018) SSR, 214:109. [2] Banfield, D. et al. (2019) SSR, 215:4. [3] Viúdez-Moreiras, et al. (2019), G. Icarus, 319, 909-925. [4] Viúdez-Moreiras, D. (2019). Icarus, 319, 645-656. [5] Newman, C.E. et al. (2019), EGU. [ABSTRACT FROM AUTHOR]

The ExoMars Trace Gas Orbiter (TGO), a mission by ESA and Roscosmos, was launched inMarch 2016 and reached its final, near-circular 400 km orbit around Mars in March, 2018. Onboard TGO, the Atmospheric Chemistry Suite (ACS) is a set of three spectrometers includinga thermal-infrared channel, TIRVIM. This Fourier-transform spectrometer covers the range600–6000 cm−1 (1.7–17μm) with a spectral resolution of 1.2 cm−1. We focus here on nadirobservations in the range 600-1300 cm−1, which covers absorption by CO2 (centered at 667cm−1), water ice clouds (centered at 820 cm−1) and dust (centered at 1100 cm−1).The advantage of the TIRVIM data set over previous instruments comes from theTGO orbit, which is not sun-synchronous and was designed to sample a completedaily cycle every 55 days. Hence, TIRVIM has the capacity to uniquely study boththe diurnal and seasonal variability of the thermal structure, dust and ice cloudopacity. We have developed a radiative transfer model coupled to a retrieval algorithm thatexploits TIRVIM spectra to simultaneously retrieve vertical profiles of the temperature from 5 to 45 km, surface temperature, and integrated optical depth of dust and water ice clouds.This algorithm was tested and validated against synthetic observations generated undervarious conditions (local time, seasons, latitude, aerosol load,...). We have thenapplied this algorithm to the first 45 days of TIRVIM data acquired in March-April,2018. The retrieved temperature profiles have been validated against thousandsof co-located measurements acquired by the Mars Climate Sounder around 3amand 3pm, a limb-viewing radiometer onboard Mars Reconnaissance Orbiter. Theagreement between the two data sets is very satisfactory. In particular, the amplitudeof the diurnal thermal tide as seen by MCS is very well captured by TIRVIM atpressures greater than 10 Pa. However, TIRVIM underestimates it in the range 1–10 Pa,which is due to a much poorer vertical resolution in this region (as expected froma nadir-viewing sounder). We will present these results with an emphasis on thediurnal cycle of the atmospheric temperature and the aerosols load, along withcomparisons with predictions from the LMD Mars GCM. Analysis of TIRVIM dataacquired during the dust storm in June-July 2018 is in progress and will also bepresented. Acknowledgements: The ACS experiment is led by IKI in Moscow. We acknowledgesupport by CNES and Roscosmos. [ABSTRACT FROM AUTHOR]

The typical resolution used in CMIP-class Earth system models limits, among others, the ability to assess climate risks that are associated with smaller-scale weather phenomena such as tropical cyclones. We introduce higher-resolution atmosphere-only simulations following the HighResMIP Tier1 protocol. A baseline simulation (LMDZ-OR) is run with LMD-Z, the atmospheric component of the IPSL-CM Earth System model, with CMIP6 physics including the land-surface model ORCHIDEE, at a resolution equivalent to 50km at mid-latitudes. Large-scale parallel I/O with on-the-fly data processing is enabled by the XIOS I/O server. In two additional simulations (ICO-LMDZ-OR), the LMD-Z latitude-longitude dynamical core is replaced by the more scalable DYNAMICO dynamical core, using icosahedral-hexagonal meshes with quasi-uniform resolution of 50km and 25km.We provide a description and preliminary analysis of these simulations. We present the scalability and throughput of LMDZ-OR and ICO-LMDZ-OR. Some differences between LMDZ-OR and ICO-LMDZ-OR with respect to the processing of input datasets, especially orography, are discussed. The climates in LMDZ-OR and ICO-LMD-OR simulations at similar resolutions are compared. Dependence on resolution of key climate features is examined. [ABSTRACT FROM AUTHOR]

The ExoMars Trace Gas Orbiter (TGO), a collaborative project between the European Space Agency and Roscosmos, was successfully inserted into Mars orbit on 19 October 2016, and reached its final science orbit on 7 April 2018. TGO began taking observations as part of commissioning operations in March 2018.At the Laboratoire de Météorologie Dynamique (LMD) we are responsible for data assimilation of observations from the Atmospheric Chemistry Suite (ACS) thermal infrared instrument (TIRVIM) on board TGO. This instrument measures vertical profiles of temperature as well as dust and water ice integrated content, at various local times, latitudes and seasons.Here we report on assimilation of the first six weeks of TIRVIM observations into the LMD Mars General Circulation Model (GCM), using the Local Ensemble Transform Kalman Filter (LETKF) technique. The LETKF is an ensemble-based assimilation scheme where we typically use 16 ensemble members and multiplicative inflation to adjust the background ensemble error covariance. The assimilation focuses on atmospheric temperatures retrieved from nadir thermal emission spectra taken between 2018 March 13 and 2018 April 28. These have been calibrated and then retrieved using a line-by-line radiative transfer model. The observations cover various local times of day with full coverage in longitude every 7-10 days, over +/- 75 degree latitude, with vertical coverage between 5-45 km altitude.We shall report on the differences between the assimilation and a free-running model, particularly at local times of day that have not been observed prior to TGO. We shall also report on progress combining assimilation of ACS observations with profiles from Mars Climate Sounder on board NASA's Mars Reconnaissance Orbiter, to fill in anticipated gaps in the ACS observational record and to sample the local time of day more fully. [ABSTRACT FROM AUTHOR]

Introduction: The Cassini spacecraft allowed a detailed characterization of Saturn's stratosphere and its seasonal variability. In particular, infrared sounding on board Cassini revealed an equatorial, periodic oscillation of stratospheric temperature, associated with a putative vertical structure of winds similar to the Earth's Quasi-Biennial Oscillation (in contrast, Saturn's oscillation is semi-annual), as well as a possible inter-hemispheric transport of stratospheric hydrocarbons reminiscent of the transport of trace species by the wave-driven Brewer-Dobson circulation on Earth and a warm stratospheric disturbance in the aftermath of the Great White Storm of 2010-2011.To address these questions and better understand Saturn's atmospheric circulation, we have developed a General Circulation Model for Saturn. It employs the new DYNAMICO icosahedral hydrodynamical core which allows us to perform simulations at an horizontal resolution of 1/2° in longitude/latitude. Such a high resolution is necessary to start resolving eddies arising from hydrodynamical instabilities and their forcing on planetary-scale dynamics. This Saturn GCM was recently used to study the tropospheric dynamics, addressing topics such as tropospheric jet formation, evolution and stability, or planetary wave activity. In the present study, we performed new simulations with the model top extended to 1 µbar in order to investigate Saturn's stratospheric circulations.Results: Our new GCM simulations for Saturn exhibit several remarkable features in the stratosphere.Firstly, equatorial winds are asymmetric: eastward jets are stronger than westward ones. The equatorial zonal jet displays a strong vertical shear with alternatively positive and negative jets stacked on the vertical. It also undergoes episodes of very fast downward propagation of the zonal wind shear extrema. This pattern is similar to a QBO-like oscillation, but the amplitude and period do not match the observed ones. However, stratospheric temperature changes are very different. Temperature fluctuates on rapid timescales and can not be associated with winds oscillation. Secondly, between the bottom of the stratosphere (40 mbar) to the model top, our simulations exhibit two tropical (at 20°N and 20°S) strong oscillations in opposition of eastward and westward winds with annual period.Perspectives: To improve the physical forcing of the QBO-like oscillation in Saturn's equatorial stratosphere, we have two possibilities inspired by Earth's atmospheric modelling. We plan to add either a stochastic gravity wave drag parametrization or a thermal plume parametrization to our GCM. Both are expected to produce a more realistic wave spectrum, which strongly impacts the simulation of the equatorial oscillation and the downward propagation of winds. We will consider the residual meridional circulation in the stratosphere and analysis of planetary-scale waves activity. [ABSTRACT FROM AUTHOR]

The entry, descent and landing of Schiaparelli, the ExoMars Entry, descent and landing Demonstrator Module (EDM), offered a rare (once-per-mission) opportunity for in situ investigations of the martian environment over a wide altitude range. The aim of the ExoMars AMELIA experiment was to exploit the Entry, Descent and Landing System (EDLS) engineering measurements for scientific investigations of Mars' atmosphere and surface. Here we present the simulations, modelling and the planned investigations prior to the Entry, Descent and Landing (EDL) event that took place on 19th October 2016. Despite the unfortunate conclusion of the Schiaparelli mission, flight data recorded during the entry and the descent until the loss of signal, have been recovered. These flight data, although limited and affected by transmission interruptions and malfunctions, are essential for investigating the anomaly and validating the EDL operation, but can also contribute towards the partial achievement of AMELIA science objectives. [ABSTRACT FROM AUTHOR]