F. Lefèvre

Université de Versailles Saint-Quentin, Versailles, Île-de-France, France

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Publications (194)392.53 Total impact

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    ABSTRACT: The 1.27-μm O2(a1Δg) dayglow on Mars is a product of the ozone photolysis by solar UV radiation. The intensity of the O2(a1Δg) emission rate depends on ozone concentration, atmospheric density and kinetic parameters of involved photochemical reactions. In turn, the distribution of ozone is sensitive to the vertical and spatial distribution of water vapor, which is an effective destructor of O3. SPICAM IR on the Mars-Express mission measures the O2(1Δg) dayglow with spectral resolving power of 2200. The results of 147 limb observations from 2004 to 2013 are reported. Limb resolution of the instrument is variable and exceeds the scale height of the atmosphere. The slant emission rate reaches a maximum at the high Northern latitudes at northern and southern springs Ls = 0–50° and 160–190°, respectively and a minimum in middle and low latitudes at southern summer Ls = 200–300°. We have compared the SPIVAM O2(a1Δg) limb profiles with the General Circulation Model simulation by the Laboratoire de Meteorologie Dynamique (LMD GCM, Lefèvre, F., Lebonnois, S., Montmessin, F., Forget, F. [2004]. J. Geophys. Res. 109, E07004. http://dx.doi.org/10.1029/2004JE002268; Lefèvre, F., et al. [2008]. Nature 454(7207), 971–975) reduced to the vertical resolution of the instrument. The GCM includes the radiative effect of the water clouds and an interactive dust scheme, and well reproduces Martian Climate Sounder (MCS) temperature profiles (Clancy, R. Todd et al. [2012]. J. Geophys. Res. 117, 10. http://dx.doi.org/10.1029/2011JE004018). The model underestimates the emission for Ls = 0–50°, Ls = 160–180° and overestimates it from Ls = 60° to Ls = 150° at high Northern latitudes. In the Southern hemisphere the model underestimates the emission for Ls = 170–200° and overestimates it for Ls = 200–230° at high Southern latitudes. The disagreement could be related to the water vapor distribution as the model reproduces it. The most recent version of the LMD GCM including microphysical representation of cloud formation taking into account the effect of dust scavenging by water ice clouds (Navarro, T., Madeleine, J.-B., Montmessin, F., Forget, F., Spiga, A., Millour, E. [2013]. Modeling of the martian water cycle with an improved representation of water ice clouds. European Planetary Science Congress 2013, EPSC Abstracts, vol. 8, EPSC2013-203) gives much better agreement with SPICAM O2(a1Δg) dayglow limb observations. Characterization of the Mars water cycle by GCMs continues to improve, and the observations of the O2(a1Δg) dayglow offer a powerful tool for its validation.
    Icarus 09/2014; 239:131–140. DOI:10.1016/j.icarus.2014.05.040 · 2.84 Impact Factor
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    ABSTRACT: We present a synthesis of the decade-long Mars Express SPICAM observations in an attempt to assemble a single, coherent picture that has implications for the long-term evolution of water and hydrogen on Mars.
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    ABSTRACT: Mesospheric CO2 ice clouds on Mars are simulated with a 1D microphysical model, which includes a crystal growth rate adapted to high supersaturations encountered in the martian mesosphere. Observational constraints (crystal radius and opacity) exist for these clouds observed during the day around the equator at ∼60–80 km altitude. Nighttime mesospheric clouds interpreted as CO2 ice clouds have also been characterized at low southern latitudes, at ∼90–100 km altitude. From modeling and observational evidence, it is believed that mesospheric clouds are formed within temperature minima created by thermal tides, where gravity wave propagation allows for the creation of supersaturated layers (cold pockets). Thus, temperature profiles perturbed by gravity waves are used in the model to initiate nucleation and maintain growth of CO2 ice crystals. We show that it is possible to reproduce the observed effective radii for daytime and nighttime clouds. Crystal sizes are mainly governed by the altitude where the cloud forms, and by the amplitude of supersaturation. The temporal and spatial behavior of the cloud is controlled by the extent and lifetime of the cold pocket. The cloud evaporates fast after the cold pocket has vanished, implying a strong correlation between gravity wave activity and CO2 cloud formation. Simulated opacities remain far below the observed ones as long as typical dust conditions are used. In the case of the lower daytime clouds, the enhanced mesospheric dust loading typically reached during dust storm conditions, allows for greater cloud opacities, close to observed values, by supplying the atmosphere with condensation nuclei. However, CO2 ice clouds are not detected during the dust storm season, and, because of fast sedimentation of dust particles, an exogenous supply (meteoritic flux) appears necessary to explain opacities of both daytime and nighttime mesospheric CO2 ice clouds along their whole period of observation.
    Icarus 07/2014; 237:239–261. DOI:10.1016/j.icarus.2014.04.022 · 2.84 Impact Factor
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    ABSTRACT: We will present results obtained with the 1D- simulations of mesospheric CO2 ice clouds within cold pockets created by gravity waves, and compare them to observations. Simple dust scenarios are pre- scribed to account for condensation nuclei, necessary to explain measured opacities.
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    The Fifth International Workshop on the Mars Atmosphere: Modelling and Observation; 12/2013
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    ABSTRACT: The Mars Color Imager (MARCI) onboard the Mars Reconnaissance Orbiter (MRO) employs ultraviolet imaging bands within (260nm) and longward (320 nm) of Hartley band ozone absorption, in support of daily global mapping retrievals for Mars atmospheric ozone columns. We present the first release of this unique global atmospheric mapping data set, consisting of 1010 ozone column retrievals spanning MY29-31 on a daily global grid of 8x8 km spatial resolution. Coincident 320nm cloud optical depth retrievals are obtained in conjunction with the MARCI ozone columns (Wolff et al, 2011). The MARCI ozone column detection limit 1 μm-atm) is appropriate to mapping elevated ozone abundances at low latitudes around Mars aphelion, and over mid-to-high latitudes during fall/winter/spring seasons. MARCI ozone maps for these regions reveal the detailed spatial and temporal behaviors of water vapor saturation conditions that force large variations in water vapor photolysis products (HOx) responsible for the catalytic destruction of ozone in the Mars atmosphere. In the context of full temporal/spatial resolution, we present aphelion increases in low latitude ozone and potential cloud and topographic correlations, high latitude ozone maxima associated with planetary waves and weather fronts during northern early spring, and surprising (yet to be explained) winter season ozone variations within the Hellas basin. Comparisons are provided for MARCI ozone measurements to ozone simulations from the Laboratory of Meteorology and Dynamics General Circulation Model (LMDGCM; Lefevre et al., 2006) and ozone measurements by the SPICAM ultraviolet spectrometer on Mars Express (Perrier et al, 2006).
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    ABSTRACT: A new approach is presented to model the condensational growth of carbon dioxide (CO2) ice crystals on Mars. These condensates form in very particular conditions. First, ∼95% of the atmosphere is composed of CO2 so that near‐pure vapor condensation takes place. Second, the atmosphere is rarefied, having dramatic consequences on the crystal growth. Indeed, the subsequently reduced efficiency of heat transport helps maintain a high temperature difference between the crystal surface and the environment, inhibiting the growth. Besides, the Stefan flow which would have been expected to increase the growth rate of the crystal, because of the near‐pure vapor condensation, is negligible. We show that the heritage of the convenient and explicit linearized crystal growth rate formula used for Earth clouds, initially derived for a trace gas, has to be reconsidered in the case of near‐pure vapor condensation for high saturation ratios that appear to be common in the Martian mesosphere. Nevertheless, by comparing our approach with a more complex condensation model, valid for all atmospheric conditions and all vapor abundances, we show that a very simple set of equations can still be used to efficiently reproduce the CO2 ice crystal growth rate. Our model, referred to as the CLASSIC model here, provides similar crystal growth rates than the traditionally used linearized growth rate models at low supersaturations but predicts lower crystal growth rates at high supersaturations. It can thus be used to model the condensational growth of CO2 ice crystals in the mesosphere where high supersaturations are observed.
    10/2013; 118(10). DOI:10.1002/jgre.20149
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    Franck Montmessin, Franck Lefèvre
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    ABSTRACT: Since the seasonal and spatial distribution of ozone on Mars was detected 1 by the ultraviolet spectrometer onboard the spacecraft Mariner 7, our understanding has evolved consider-ably thanks to parallel efforts in observations and modelling 2–7 . At low-to-mid latitudes, martian ozone is distributed vertically in two main layers, a near-surface layer and a layer at an alti-tude between 30 and 60 km (ref. 5). Here we report evidence from the SPICAM UV spectrometer onboard the Mars Express orbiter for the existence of a previously overlooked ozone layer that emerges in the southern polar night at 40–60 km in altitude, with no counterpart observed at the north pole. Comparisons with global climate simulations for Mars indicate that this layer forms as a result of the large-scale transport of oxygen-rich air from sunlit latitudes to the poles, where the oxygen atoms recombine to form ozone during the polar night. However, transport-driven ozone formation is counteracted in our simulations by the destruction of ozone by reactions with hydrogen radicals, whose concentrations vary seasonally on Mars, reflecting seasonal variations of water vapour. We conclude that the observed dichotomy between the ozone layers of the two poles, with a significantly richer layer in the southern hemisphere, can be explained by the interplay of these mechanisms. The ozone layer on Mars is typically 3,000 times thinner than on Earth, but exhibits orders of magnitude variations in space and time as a consequence of photolysis, atmospheric dynamics and of the catalytic destruction cycles induced by the hydrogen radicals (HO x) released by water molecule dissociation. An anti-correlation between O 3 and H 2 O is therefore suspected to take place in the atmosphere of Mars, a prediction that has been confirmed by ozone observations performed from the Earth 2,3 and from satellites in orbit around Mars 4 . A compilation of night-time ozone profiles was made with the SPICAM UV spectrometer on Mars Express 5 that covers the northern spring equinox (solar longitude L s = 8 •) to northern winter solstice (L s = 270 •) time frame. These observations along with theoretical studies 5–7 have allowed characterization of the night-time ozone vertical distribution at mid-to-low latitudes, allowing the clear distinction between the near-surface layer, the top of which is perceptible below 30 km, and the elevated layer, which is present only around aphelion. The near-surface layer existence is promoted by ultraviolet screening by CO 2 molecules, which inhibits HO x production through H 2 O photolysis. The elevated layer of ozone appears essentially at night as O 3 is rapidly photolysed after sunrise. Its magnitude is controlled by HO x concentration above 25 km. For this reason, seasonal variations of the water saturation level exert a strong modulation of the elevated layer of ozone in the tropics, forcing O 3 to maximize around the northern summer solstice (that is, the aphelion season) when temperatures are lowest and to vanish soon after L s ∼ 130 • . In the polar regions, H 2 O is LATMOS – CNRS/UVSQ/UPMC, 11 bd d'Alembert, 78280 Guyancourt, France. *e-mail: franck.montmessin@latmos.ipsl.fr Latitude 70° S¬80° S 10 7 10 8 10 9 10 10 O 3 density (molecules per cm 3) 0 20 40 60 80 a b L s (°) 40¬60 60¬80 80¬100 L s 60¬80° 0.01 0.10 1.00 10.00 O 3 volume mixing ratio (ppmv) 0 20 40 60 80 Latitude 10° S 30° S 50° S 75° S Altitude (km) Altitude (km) Figure 1 | A synthesis of SPICAM data showing the prominent southern polar ozone layer around 50 km. a, A series of ozone profiles observed from 2004 to 2011 by SPICAM between 70 • S and 80 • S and covering solar longitude (L s) 40 • –100 • . The colour coding distinguishes three periods to highlight the seasonal peak at L s ∼ 70 • (red curves). b, Profiles of O 3 given in volume mixing ratio (O 3 number density ratioed to the atmospheric number density of the GCM, in ppmv) at the time of the seasonal peak and averaged within four latitudinal intervals from the south pole to the equator. minimum in autumn and winter. The O 3 column is in turn found to be maximum, and large concentrations are found in the first 25 km above the surface 5 . The results reported here concern the identification from the SPICAM night-time data set of a previously overlooked ozone layer
    Nature Geoscience 09/2013; DOI:10.1038/NGEO1957 · 11.67 Impact Factor
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    ABSTRACT: The international research project RECONCILE has addressed central questions regarding polar ozone depletion, with the objective to quantify some of the most relevant yet still uncertain physical and chemical processes and thereby improve prognostic modelling capabilities to realistically predict the response of the ozone layer to climate change. This overview paper outlines the scope and the general approach of RECONCILE, and it provides a summary of observations and modelling in 2010 and 2011 that have generated an in many respects unprecedented dataset to study processes in the Arctic winter stratosphere. Principally, it summarises important outcomes of RECONCILE including (i) better constraints and enhanced consistency on the set of parameters governing catalytic ozone destruction cycles, (ii) a better understanding of the role of cold binary aerosols in heterogeneous chlorine activation, (iii) an improved scheme of polar stratospheric cloud (PSC) processes that includes heterogeneous nucleation of nitric acid trihydrate (NAT) and ice on non-volatile background aerosol leading to better model parameterisations with respect to denitrification, and (iv) long transient simulations with a chemistry-climate model (CCM) updated based on the results of RECONCILE that better reproduce past ozone trends in Antarctica and are deemed to produce more reliable predictions of future ozone trends. The process studies and the global simulations conducted in RECONCILE show that in the Arctic, ozone depletion uncertainties in the chemical and microphysical processes are now clearly smaller than the sensitivity to dynamic variability.
    ATMOSPHERIC CHEMISTRY AND PHYSICS 09/2013; DOI:10.5194/acpd-12-30661-2012 · 5.30 Impact Factor
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    ABSTRACT: Visible and near-IR Meinel band emissions originate from excited OH in the terrestrial upper atmosphere (Meinel, I.A.B. [1950]. Astrophys. J. 111, 555. http://dx.doi.org/10.1086/145296), and have recently been detected in the Venus nightside upper mesosphere (Piccioni, G. et al. [2008]. Astron. Astrophys. 483, L29–L33. http://dx.doi.org/10.1051/0004-6361:200809761). Meinel band observations support key studies of transport and photochemistry in both of these atmospheres. In the case of Mars, OH regulates the basic stability of the CO2 atmosphere to photolytic decomposition (to CO and O2, e.g. Parkinson, T.D., Hunten, D.M. [1972]. J. Atmos. Sci. 29, 1380–1390. http://dx.doi.org/10.1175/1520-0469(1972)029<1380:SAAOOO>2.0.CO;2), and yet has never been measured. We present the first detection of Mars atmospheric OH, associated with CRISM near-IR spectral limb observations of polar night Meinel band emissions centered at 1.45 and 2.9 μm. Meinel band (1–0), (2–1), and (2–0) average limb intensities of 990 ± 280, 1060 ± 480, and 200 ± 100 kiloRayleighs (kR), respectively, are determined for 70–90 NS polar winter latitudes over altitudes of 40–56 km. Additional OH bands, such as (3–2), (3–1), and (4–2), present ⩽1σ measurements. Uncertainty in the (4–2) band emission rate contributes to increased uncertainty in the determination of the O2(1Δg) (0–0)/(0–1) band emission ratio A00/A01=47-12+26. An average profile retrieval for Mars OH polar nightglow indicates 45–55 km altitude levels for volume emission rates (VER) of 0.4 (2–0) to 2 (1–0, 2–1) × 104 photons/(cm3 s). Similar to polar night O2(1Δg) emission (e.g. Clancy, R.T. et al. [2012]. J. Geophys. Res. (Planets) 117, E00J10. http://dx.doi.org/10.1029/2011JE004018), Meinel OH band emission is supported by upper level, winter poleward transport of O and H in the deep Hadley solsticial circulations of Mars. The retrieved OH emission rates are compared to polar winter OH nightglow simulated by the LMD (Laboratoire de Météorologie Dynamique) photochemical GCM (global climate model), employing detailed photochemistry (e.g. Lefèvre, F., Lebonnois, S., Montmessin, F., Forget, F. [2004]. J. Geophys. Res. (Planets) 109, E07004. http://dx.doi.org/10.1029/2004JE002268) and energy transfer processes (excitation and quenching) developed for Mars Meinel OH band nightglow by García Muñoz et al. (García Muñoz, A., McConnell, J.C., McDade, I.C., Melo, S.M.L. [2005]. Icarus 176, 75–95). Modeled versus observed OH emission behavior agrees within measurement uncertainties with the assumptions of a Bates–Nicolet (H + O3) source for excited OH production, and ‘collisional-cascade’ quenching of the OH vibrational population by CO2. ‘Sudden-death’ quenching of excited OH by CO2 leads to 100× less OH emission than observed. The combined agreement between LMD GCM simulated and CRISM observed O2(1Δg) and Meinel OH polar nightglow behaviors represents a significant demonstration of the LMD model capability to couple odd oxygen and hydrogen photochemistry and transport by the Mars global circulation in a realistic fashion.
    Icarus 09/2013; 226(1):272–281. DOI:10.1016/j.icarus.2013.05.035 · 2.84 Impact Factor
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    ABSTRACT: Observations of ozone, a trace gas on Mars, have the potential to constrain atmospheric dynamical and physical processes. Current Mars Global Circulation Models (MGCMs) [1, 2, 3] are able to represent the photochemistry occuring in the atmosphere, with comparisons to observations used to confine particular species. However, a long term comparison using data assimilation provides a more robust constraint on the model. We have assimilated total-ozone observations from SPICAM into an MGCM to study the Martian ozone cycle. Ozone has never before been assimilated for an extraterrestrial planet. Our aim is to use ozone to provide a preliminary technique for trace gas data assimilation for the analysis of observations from current and future satellite missions (such as ExoMars) which observe the spatial and temporal distribution of trace gases on Mars.
    European Planetary Science Congress 2013; 09/2013

Publication Stats

2k Citations
392.53 Total Impact Points

Institutions

  • 2006–2014
    • Université de Versailles Saint-Quentin
      • Laboratoire des Sciences du Climat et de l'Environnement (LSCE)
      Versailles, Île-de-France, France
    • Spanish National Research Council
      • Andalusian Astrophysics Institute
      Madrid, Madrid, Spain
  • 1998–2014
    • French National Centre for Scientific Research
      • Laboratoire de météorologie dynamique (LMD)
      Lutetia Parisorum, Île-de-France, France
  • 2009–2013
    • LATMOS
      Guyancourt, Île-de-France, France
  • 2002–2012
    • Pierre and Marie Curie University - Paris 6
      • Laboratoire de météorologie dynamique (LMD)
      Lutetia Parisorum, Île-de-France, France
    • Institut Pierre Simon Laplace
      Lutetia Parisorum, Île-de-France, France
  • 2008
    • LHC France
      Lutetia Parisorum, Île-de-France, France
  • 1997–1999
    • Météo-France
      Lutetia Parisorum, Île-de-France, France
  • 1996
    • Centre National de Recherches Météorologiques
      Tolosa de Llenguadoc, Midi-Pyrénées, France