lmd_Madeleine2012_abstracts.html

2012 .

J.-B. Madeleine, F. Forget, E. Millour, T. Navarro, and A. Spiga. The influence of radiatively active water ice clouds on the Martian climate. Geophysical Research Letters, 39:23202, December 2012. [ bib | DOI | ADS link ]

Radiatively active water ice clouds (RAC) play a key role in shaping the thermal structure of the Martian atmosphere. In this paper, RAC are implemented in the LMD Mars Global Climate Model (GCM) and the simulated temperatures are compared to Thermal Emission Spectrometer observations over a full year. RAC change the temperature gradients and global dynamics of the atmosphere and this change in dynamics in turn implies large-scale adiabatic temperature changes. Therefore, clouds have both a direct and indirect effect on atmospheric temperatures. RAC successfully reduce major GCM temperature biases, especially in the regions of formation of the aphelion cloud belt where a cold bias of more than 10 K is corrected. Departures from the observations are however seen in the polar regions, and highlight the need for better modeling of cloud formation and evolution.

R. T. Clancy, B. J. Sandor, M. J. Wolff, M. D. Smith, F. Lefèvre, J.-B. Madeleine, F. Forget, S. L. Murchie, F. P. Seelos, K. D. Seelos, H. A. Nair, A. D. Toigo, D. Humm, D. M. Kass, A. Kleinböhl, and N. Heavens. Extensive MRO CRISM observations of 1.27 μm O₂ airglow in Mars polar night and their comparison to MRO MCS temperature profiles and LMD GCM simulations. Journal of Geophysical Research (Planets), 117:0, August 2012. [ bib | DOI | ADS link ]

The Martian polar night distribution of 1.27 μm (0-0) band emission from O₂ singlet delta [O₂(¹Δ_g)] is determined from an extensive set of Mars Reconnaissance Orbiter (MRO) Compact Reconnaissance Imaging Spectral Mapping (CRISM) limb scans observed over a wide range of Mars seasons, high latitudes, local times, and longitudes between 2009 and 2011. This polar nightglow reflects meridional transport and winter polar descent of atomic oxygen produced from CO₂ photodissociation. A distinct peak in 1.27 μm nightglow appears prominently over 70-90NS latitudes at 40-60 km altitudes, as retrieved for over 100 vertical profiles of O₂(¹Δ_g) 1.27 μm volume emission rates (VER). We also present the first detection of much (×80 20) weaker 1.58 μm (0-1) band emission from Mars O₂(¹Δ_g). Co-located polar night CRISM O₂(¹Δ_g) and Mars Climate Sounder (MCS) (McCleese et al., 2008) temperature profiles are compared to the same profiles as simulated by the Laboratoire de Météorologie Dynamique (LMD) general circulation/photochemical model (e.g., Lefèvre et al., 2004). Both standard and interactive aerosol LMD simulations (Madeleine et al., 2011a) underproduce CRISM O₂(¹Δ_g) total emission rates by 40%, due to inadequate transport of atomic oxygen to the winter polar emission regions. Incorporation of interactive cloud radiative forcing on the global circulation leads to distinct but insufficient improvements in modeled polar O₂(¹Δ_g) and temperatures. The observed and modeled anti-correlations between temperatures and 1.27 μm band VER reflect the temperature dependence of the rate coefficient for O₂(¹Δ_g) formation, as provided in Roble (1995).

J.-B. Madeleine, F. Forget, A. Spiga, M. J. Wolff, F. Montmessin, M. Vincendon, D. Jouglet, B. Gondet, J.-P. Bibring, Y. Langevin, and B. Schmitt. Aphelion water-ice cloud mapping and property retrieval using the OMEGA imaging spectrometer onboard Mars Express. Journal of Geophysical Research (Planets), 117:0, May 2012. [ bib | DOI | ADS link ]

Mapping of the aphelion clouds over the Tharsis plateau and retrieval of their particle size and visible opacity are made possible by the OMEGA imaging spectrometer aboard Mars Express. Observations cover the period from MY26 L_s = 330deg to MY29 L_s = 180deg and are acquired at various local times, ranging from 8 AM to 6 PM. Cloud maps of the Tharsis region constructed using the 3.1 μm ice absorption band reveal the seasonal and diurnal evolution of aphelion clouds. Four distinct types of clouds are identified: morning hazes, topographically controlled hazes, cumulus clouds and thick hazes. The location and time of occurrence of these clouds are analyzed and their respective formation process is discussed. An inverse method for retrieving cloud particle size and opacity is then developed and can only be applied to thick hazes. The relative error of these measurements is less than 30% for cloud particle size and 20% for opacity. Two groups of particles can be distinguished. The first group is found over flat plains and is composed of relatively small particles, ranging in size from 2 to 3.5 μm. The second group is characterized by particle sizes of 5 μm which appear to be quite constant over L_s and local time. It is found west of Ascraeus and Pavonis Mons, and near Lunae Planum. These regions are preferentially exposed to anabatic winds, which may control the formation of these particles and explain their distinct properties. The water ice column is equal to 2.9 pr.μm on average, and can reach 5.2 pr.μm in the thickest clouds of Tharsis.

L. Kerber, J. W. Head, J.-B. Madeleine, F. Forget, and L. Wilson. The dispersal of pyroclasts from ancient explosive volcanoes on Mars: Implications for the friable layered deposits. Icarus, 219:358-381, May 2012. [ bib | DOI | ADS link ]

A number of voluminous, fine-grained, friable deposits have been mapped on Mars. The modes of origin for these deposits are debated. The feasibility for an origin by volcanic airfall for the friable deposits is tested using a global circulation model to simulate the dispersal of pyroclasts from candidate source volcanoes near each deposit. It is concluded that the Medusae Fossae Formation and Electris deposits are easily formed through volcanic processes, and that the Hellas deposits and south polar pitted deposits could have some contribution from volcanic sources in specific atmospheric regimes. The Arabia and Argyre deposits are not well replicated by modeled pyroclast dispersal, suggesting that these deposits were most likely emplaced by other means.

J. L. Fastook, J. W. Head, D. R. Marchant, F. Forget, and J.-B. Madeleine. Early Mars climate near the Noachian-Hesperian boundary: Independent evidence for cold conditions from basal melting of the south polar ice sheet (Dorsa Argentea Formation) and implications for valley network formation. Icarus, 219:25-40, May 2012. [ bib | DOI | ADS link ]

Currently, and throughout much of the Amazonian, the mean annual surface temperatures of Mars are so cold that basal melting does not occur in ice sheets and glaciers and they are cold-based. The documented evidence for extensive and well-developed eskers (sediment-filled former sub-glacial meltwater channels) in the south circumpolar Dorsa Argentea Formation is an indication that basal melting and wet-based glaciation occurred at the South Pole near the Noachian-Hesperian boundary. We employ glacial accumulation and ice-flow models to distinguish between basal melting from bottom-up heat sources (elevated geothermal fluxes) and top-down induced basal melting (elevated atmospheric temperatures warming the ice). We show that under mean annual south polar atmospheric temperatures (-100 degC) simulated in typical Amazonian climate experiments and typical Noachian-Hesperian geothermal heat fluxes (45-65 mW/m²), south polar ice accumulations remain cold-based. In order to produce significant basal melting with these typical geothermal heat fluxes, the mean annual south polar atmospheric temperatures must be raised from today's temperature at the surface (-100 degC) to the range of -50 to -75 degC. This mean annual polar surface atmospheric temperature range implies lower latitude mean annual temperatures that are likely to be below the melting point of water, and thus does not favor a ”warm and wet” early Mars. Seasonal temperatures at lower latitudes, however, could range above the melting point of water, perhaps explaining the concurrent development of valley networks and open basin lakes in these areas. This treatment provides an independent estimate of the polar (and non-polar) surface temperatures near the Noachian-Hesperian boundary of Mars history and implies a cold and relatively dry Mars climate, similar to the Antarctic Dry Valleys, where seasonal melting forms transient streams and permanent ice-covered lakes in an otherwise hyperarid, hypothermal climate.