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Our Global Climate Model (GCM) of the Martian atmosphere is the result of twenty years of ongoing collaboration between our teams and has matured to the point of enabling to study the main cycles (dust, CO2, water) of present-day and past Martian climates. \ud At the 2014 scientific assembly, we will report on the latest developments and improvements of our GCM, and also present the latest version of the Mars Climate Database (version 5.1) that is derived from GCM outputs, along with comparisons with available measurements (from TES, MCS, Viking, Phoenix, Curiosity, etc.).

As is the case on Earth, atmospheric gravity waves are ubiquitous and play a key role on Mars. We recently obtained new results on Martian gravity waves by combining the latest remote sensing observations with Martian mesoscale modeling. Many independent measurements have shown that extremely low temperatures ("cold pockets") are found in the Martian mesosphere. Recent observational achievements also hint at such cold pockets by revealing mesospheric clouds formed through the condensation of CO2, the major component of the Martian atmosphere. We show that, in combination with large-scale thermal tides, mesoscale gravity waves are crucial for creating mesospheric cold pockets propitious to CO2 condensation. Most of regions/seasons featuring mesospheric CO2 clouds are characterized by atmospheric conditions favorable to the upward propagation of gravity waves from tropospheric sources. How gravity waves contribute to form CO2 clouds is reminiscent of their role in the formation of polar stratospheric clouds with relatively high optical depths on Earth. We also report how airglow imagery is a powerful method to detect and study the propagation of Martian gravity waves. This technique has already proved powerful in the case of terrestrial gravity waves. Wave patterns in the southern polar region of Mars were found in O2 dayglow maps obtained at 1.27 μm with the imaging spectrometer OMEGA on board Mars Express. We show through mesoscale modeling that the propagation of gravity waves in the Martian troposphere could explain these patterns. Model predictions match the intensity and spatial variability of dayglow fluctuations observed in the OMEGA maps. We finally propose to make gravity wave activity a plausible explanation for the "cloud trails" recently discovered by the high-resolution color imager MARCI on board Mars Reconnaissance Orbiter. The name of those clouds reflect their extended longitudinal dimensions, which develop within less than two hours. Cloud trails appear at altitudes 40 - 50 km, only above very specific regions, at the warmest season (perihelion) and local time (early afternoon). Those characteristics appear paradoxical, given atmospheric temperatures at which Martian water ice clouds usually form. We show however that a possible explanation involves gravity waves emitted by turbulent convection in the highly unstable Martian boundary layer which vertical extent could reach one atmospheric scale height. Further studies are needed on convectively-generated gravity waves on Mars, to complement existing work on the orographic source. In addition to boundary layer convection, recent modeling shows indeed that dust-induced deep convection within Martian dust storms could trigger gravity waves.

International audience; We report observations of NO nightglow with the SPICAM experiment on board the Mars Express (MEx) spacecraft. NO molecules emit a UV photon when N and O atoms (produced at high altitude in the thermosphere) recombine. Therefore, this emission is a tracer of the atmospheric dynamics in the in the lower thermosphere where O and N atoms are produced, and below, in the altitude region 50-100 km where the emission is detected. A new retrieval method has been developed to analyse the measurements from this instrument in the stellar occultation mode without slit, and retrieve the absolute brightness of the emission. We present the results from the processing of more than 2000 orbits, providing the first global latitude-season distribution of the emission, established over three Martian years. The results are globally consistent with previously available measurements of dedicated limb nightglow obtained during the first Martian year of MEx (MY27). We compared the ensemble of both data sets withthe predictions of the LMD-MGCM, with the addition of the full chemistry of N atoms. We find an overall agreement between the observed and modelled airglow intensities, but discrepancies are also found. The frequency and magnitude of the NO airglowobservations show important asymmetries between the Northern and the Southern hemispheres. There is no detection of emission near the poles during equinox conditions, while the model predicts that it should be most intense because of a circulation with two descending branches at the poles.

International audience; We use a three-dimensional atmospheric model to study the airglow emissions from molecular oxygen in the Martian atmosphere. We estimate the O2 Herzberg I and II, the Chamberlain, and the Infrared Atmospheric band emissions from different sets of kinetic parameters available in the literature. As expected, the enhanced production of atomic oxygen during daytime leads to stronger emissions at 12 hour local time than at 00 hour local time. Nevertheless, at night, the strongest emissions are found in the subtropics and around the terminator where the photochemistry of atomic oxygen is more active. Among the simulated emissions, we find that the Infrared Atmospheric emission is the most intense, as expected, and has maximum intensity reaching a few megarayleighs over the poles during the equinoctial seasons, and an average intensity over the equatorial latitudes of 50 kilorayleighs. We investigate the impact of different levels of water and dust content on airglow and we observe that the airglow structure is modulated by variations in the background atmospheric conditions. Moreover, comparisons of the emission with observations from instruments on board Mars orbiters and with ground-based measurements from Earth allow us to validate the consistency of our airglow model. Finally, we observe that the emission profiles from all band systems show structures; a double-layer profile is very frequent, and is representative of the vertical distribution of the current measurements of O2 nightglow. This paper emphasizes the advantage of using three-dimensional global circulation models for the diagnostic of O2 photochemistry in CO2-dominated atmospheres.

International audience

International audience; We will present 3 Martian years (Mars Years 27-29) of high-altitude CO2 cloud data from MEx/OMEGA and selected results from Mex/HRSC. OMEGA observed these clouds on 51 and HRSC in 28 orbits with 11 simultaneous observations. The 3-year dataset shows that the cloud activity starts latest at Ls=0° (with the earliest occurrence observed at the end of MY 29 at Ls=330°), and continues until Ls=60° when ceasing for a period before the summer solstice. The activity starts again at or after Ls=90°, and after Ls=120° the equatorial clouds are nearly absent in our dataset. Three cases of midlatitude autumn/winter clouds have been observed: one in the northern hemisphere and two in the southern. The spatial distribution of the clouds is limited in a latitude range of 20°S-20°N (with the exceptions of the midlatitude clouds) and a longitude range -120 - 30°E (3 exceptions). The HRSC stereo observations enable accurate cloud altitude measurements, yielding values between 60 and 85 km (+/-2 km) for the near-equatorial clouds. The clouds speeds, related to the prevailing east-west winds, range from 15 to 107 m/s (+/-15 m/s). Two cloud shadow observations show that cloud opacities can go up to τ=0.6 and the cloud particle effective radii are mainly in the range reff=1-2 μm. A comparison with the LMD Mars Global Climate Model shows a good agreement between the model-predicted winds and those observed by the HRSC. The LMD-MGCM predicts a strong diurnal variation of temperature at the cloud observation altitudes due to the propagation of the diurnal thermal tide. The coldest temperatures in the near-equator cloud altitude range (60-85 km) are observed towards the end of the afternoon, whereas the warmest temperatures are found in the early morning hours. Most of the observed clouds are cirrus-type, filamented clouds, but in some OMEGA observations the clouds exhibit round, clumpy structures that have been suggested to be of convective origin. We assess the plausibility of the hypothesis of mesospheric convection in light of the observations and theoretical Convective Available Potential Energy calculations. Estimates of convective potential and vertical velocities based on observed cloud properties suggest that the convective clouds could most likely be clusters of smaller scale convective updrafts. To attain the estimated values of CAPE and vertical velocity, most probably only moderate deviations from saturation are required. Based on nucleation modeling, such deviations may imply cloud formation via heterogeneous nucleation onto small condensation nuclei.

Tesis realizada en colaboración con el Instituto de Astrofísica de Andalucía, CSIC, Tesis Univ. Granada. Departamento de Física Aplicada. Leída el 2 de junio de 2006

For many years, several teams around the world have developed GCMs (General Circulation Model or Global Climate Model) to simulate the environment on Mars. The GCM developed at the Laboratoire de Météorologie Dynamique in 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 and CNES is currently used for many applications. Its outputs have also regularly been 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 150 teams around the world. Following the recent improvements in the GCM, a new series of reference simulations have been run and compiled into a new version (version5.1) of the Mars Climate Database, released in the first half of 2014. \ud To summarize, MCD v5.1 provides: \ud - Climatologies over a series of dust scenarios: standard 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 differ from those of previous versions of the MCD (version 4.x) as they have been derived from home-made, instrument-derived (TES, THEMIS, MCS, MERs), dust climatology of the last 8 Martian years. \ud - 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], ... \ud - 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. \ud - The possibility to reconstruct realistic conditions by combining the provided climatology with additional large scale and small scale perturbations schemes. \ud 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) or landers (Viking, Phoenix, MSL).