Slimane Bekki

UPMC, Pittsburgh, Pennsylvania, United States

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Publications (29)43.97 Total impact

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    ABSTRACT: Recent works have shown how the study of stratospheric background aerosol i.e. in periods uninfluenced by major volcanic eruption seems more complex as it is now performed by more accurate means. We propose a re-analysis of Global Ozone Monitoring by Occultation of Stars GOMOS level 1b data for the period August 2002–July 2006, using the LPC2E processor algorithm, which was developed for the retrieval of aerosol extinction in the middle and upper stratosphere. The main differences with regard to the ‘official’ algorithm are the correction of chromatic scintillation, the spectral domain which has been restricted to the 400–700 nm region, the use of a Differential Optical Absorption Spectroscopy DOAS method for species retrieval, and the use of a fourth-order polynomial to reproduce the wavelength dependence of extinction. Since GOMOS observations are performed using stars of different magnitude and colour, discrepancy in signal-to-noise ratio between several profiles exists, and a data selection concerning standard deviation of aerosol extinction and other parameters becomes necessary. In the middle stratosphere, aerosol extinction profiles obtained with the LPC2E processor seem to be in better agreement with the SAGE III observations and sparse balloon-borne measurements than the ‘official products’. We present global coverage of the 500 nm extinction values from around 15–60 km, and the wavelength dependence in the 400–675 nm spectral range which gives information about the nature of the particles. The well-known layer of liquid aerosols can be observed in the lower stratosphere, where the value of extinction is greater for blue than for red wavelengths, as is typical for small droplets. In the middle stratosphere, relatively high extinction values are found, probably due to the presence of solid particles above 30 km at all latitudes. The presence of soot and interplanetary material in the middle atmosphere is discussed, as well as seasonal patterns common to the several years of analysis, such as the stratospheric cleansing of aerosols above 30 km during polar winters.
    International Journal of Remote Sensing 07/2013; 34(14):4986-5029. · 1.36 Impact Factor
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    ABSTRACT: We present a summary of the scientific objectives, payload and mission profile of the Space Weather & Ultraviolet Solar Variability Microsatellite Mission (SWUSV) proposed to CNES and ESA (small mission).
    Luc Damé (2013). The Space Weather & Ultraviolet Solar Variability Microsatellite Mission (SWUSV) . Proceedings of the International Astronomical Union, 8, pp 525-526., china; 06/2013
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    ABSTRACT: We present the ambitions of the SWUSV (Space Weather and Ultraviolet Solar Variability) Microsatellite Mission that encompasses three major scientific objectives: (1) Space Weather including the prediction and detection of major eruptions and coronal mass ejections (Lyman-Alpha and Herzberg continuum imaging); (2) solar forcing on the climate through radiation and their interactions with the local stratosphere (UV spectral irradiance from 180 to 400 nm by bands of 20 nm, plus Lyman-Alpha and the CN bandhead); (3) simultaneous radiative budget of the Earth, UV to IR, with an accuracy better than 1% in differential. The paper briefly outlines the mission and describes the five proposed instruments of the model payload: SUAVE (Solar Ultraviolet Advanced Variability Experiment), an optimized telescope for FUV (Lyman-Alpha) and MUV (200–220 nm Herzberg continuum) imaging (sources of variability); UPR (Ultraviolet Passband Radiometers), with 64 UV filter radiometers; a vector magnetometer; thermal plasma measurements and Langmuir probes; and a total and spectral solar irradiance and Earth radiative budget ensemble (SERB, Solar irradiance & Earth Radiative Budget). SWUSV is proposed as a small mission to CNES and to ESA for a possible flight as early as 2017–2018.
    Journal of Advanced Research. 05/2013; 4(3):235–251.
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    ABSTRACT: Atmospheric water vapour has a very important effect on the climate and the weather. Instruments developed last decades are providing total columns with a very good accuracy, usually of the order of less than 10% of relative value, but inter comparison between results has not been fully explored because of the diversity of the origin of the instruments (from astronomy to meteorology) and therefore, because of the diversity of scientific teams: tropospheric water vapour experts at "Meteo France", measurements of stratospheric minor constituents like ozone by UV visible spectrometry, astronomers, etc.... At Observatoire de Haute Provence, many instruments are able to measure atmospheric water vapour, total columns and/or vertical profiles as well as rain and clouds. A dedicated campaign DEMEVAP (DEvelopment of MEthods for remote sensing of water VAPor) has been organized at Observatoire de Haute Provence, South of France, in Octobre 2011 to compare and validate results of measurements. Ground based observations were compared to satellite observations and to meteorological analysis integrated amounts. Data from Sophie, the very high resolution spectrometer on the astronomical telescope of 1.96 cm; Schiamachy, GPS and SAOZ instruments as well as NCEP and ECMWF analysis are compared. This paper presents the instruments, followed by results as the agreement between instruments, discussion as the sources of differences, and the conclusion.
    04/2013;
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    ABSTRACT: Climate change is expected to increase winter rainfall and flooding in many extratropical regions as evaporation and precipitation rates increase, storms become more intense and storm tracks move polewards. Here, we show how changes in stratospheric circulation could play a significant role in future climate change in the extratropics through an additional shift in the tropospheric circulation. This shift in the circulation alters climate change in regional winter rainfall by an amount large enough to significantly alter regional climate change projections. The changes are consistent with changes in stratospheric winds inducing a change in the baroclinic eddy growth rate across the depth of the troposphere. A change in mean wind structure and an equatorward shift of the tropospheric storm tracks relative to models with poor stratospheric resolution allows coupling with surface climate. Using the Atlantic storm track as an example, we show how this can double the predicted increase in extreme winter rainfall over Western and Central Europe compared to other current climate projections. KeywordsClimate change–Europe–Stratosphere–Storm track
    Climate Dynamics 01/2012; · 4.23 Impact Factor
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    ABSTRACT: Stratospheric final warmings can be used to improve predictability of the NAOInterannual variability is seen in vertical profile of NH final warmingsMonthly mean data from GCMs reproduce these features well
    Journal of Geophysical Research Atmospheres 01/2011; 116(2011-09-29-D18113):1-11. · 3.44 Impact Factor
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    ABSTRACT: The project ORACLE-O3 ("Ozone layer and UV RAdiation in a changing CLimate Evaluated during IPY") is one of the coordinated international proposals selected for the International Polar Year (IPY). As part of this global project, LOLITA-PSC ("Lagrangian Observations with Lidar Investigations and Trajectories in Antarctica and Arctic, of PSC") is devoted to Polar Stratospheric Clouds (PSC) studies. Indeed, understanding the formation and evolution of PSC is an important issue to quantify the impact of climate changes on their frequency of formation and, further, on chlorine activation and subsequent ozone depletion. In this framework, three lidar stations performed PSC observations in Antarctica during the 2006, 2007, and 2008 winters: Davis (68.58°S, 77.97°E), McMurdo (77.86°S, 166.48°E) and Dumont D'Urville (66.67°S, 140.01°E). The data are completed with the lidar data from CALIOP ("Cloud-Aerosol Lidar with Orthogonal Polarization") onboard the CALIPSO ("Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation") satellite. Lagrangian trajectory calculations are used to identify air masses with PSCs sounded by several ground-based lidar stations with the same method, called MATCH, applied for the first time in Arctic to study the ozone depletion with radiosoundings. The evolution of the optical properties of the PSCs and thus the type of PSCs formed (supercooled ternary solution, nitric acid trihydrate particles or ice particles) could thus be linked to the thermodynamical evolution of the air mass deduced from the trajectories. A modeling with the microphysical model of the Danish Meteorological Institute allows assessing our ability to predict PSCs for various environmental conditions. Indeed, from pressure and temperature evolution, the model allows retrieving the types of particles formed as well as their mean radii, their concentrations and could also simulate the lidar signals. In a first step, a case in August 2007 around 17-18 km, involving the three ground-based lidar stations and CALIOP has been selected. Trajectories with different models (gscf and ecmwf), grids and initializations have been computed to test the robustness of the MATCH. Then the DMI model has been used with these different trajectories to test its ability to reproduce the observations. For a same case, the temperature differences (~2-3 K) between the trajectories have a strong impact on the number density of the particles formed (factor 1000). This case is presented here in detail and a statistical comparison is planned with the numerous MATCH cases identified during the three winters and which involve most of the time two ground-based lidar stations with CALIOP.
    05/2010;
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    ABSTRACT: Stratospheric aerosol optical depth: comparison of global model results with SAGE II and HALOE observations in the visible and near-, far-infrared channels G. Pitari (1), N. De Luca (1), E. Mancini (1), S. Bekki (2), M. Mills (3), C. Timmreck (4), D. Weisenstein (5) (1) Università degli Studi de L'Aquila, L'Aquila, Italy (2) Université Pierre e Marie Curie, Paris, France (3) University of Colorado, Boulder, CO, USA (4) Max-Planck Institut für Meteorologie, Hamburg, Germany (5) Atmospheric and Environmental Research, Inc., Lexington, MA, USA Stratospheric aerosols have been recognized to play an important role in the global climate system by influencing the Earth radiative balance and by providing a surface for heterogeneous chemistry. The accurate modeling of the shape and characteristics of the stratospheric aerosol layer requires the knowledge of their microphysical properties and the atmospheric distribution of their tropospheric precursor gases (SO2, OCS). The background aerosol distribution in the stratosphere may be sporadically perturbed for a time period of about five years after major explosive volcanic eruptions, that may inject in the stratosphere large amounts of SO2 and H2S. The most extensive coverage of the stratospheric aerosol distribution has been made using instruments on board of satellites (SAGE and HALOE in particular). Here we compare the distribution of stratospheric aerosols calculated by five global models with aerosol modules on-line against satellite observations. The results of two 3-D models (MPI and ULAQ) and three 2-D models (AER, LASP, UPMC) are used for this comparison, for both non-volcanic and volcanically perturbed conditions. The comparison is made in terms of aerosol extinction and optical depth: these are calculated using Mie scattering programs where the model calculated aerosol mass distribution is used as input as a function of the particle radius. The size distribution calculated in the models is the final product of several physical and chemical mechanisms (emission of gas precursors, large-scale transport, oxidation and photolysis of precursors, aerosol formation via homogeneous and heterogeneous nucleation, aerosol growth via coagulation and gas condensation and aerosol removal via gravitational settling and tropospheric washout. The comparison of stratospheric aerosol optical depth with satellite observations is used to evaluate the performances of the models and to identify gaps in our understanding of aerosol processes and/or deficiencies in their representation in models. The Pinatubo eruption of June 1991 is used as case study for the volcanically perturbed stratosphere.
    05/2010;
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    ABSTRACT: A multimodel assessment of the performance of chemistry‐climate models (CCMs) in the extratropical upper troposphere/lower stratosphere (UTLS) is conducted for the first time. Process‐oriented diagnostics are used to validate dynamical and transport characteristics of 18 CCMs using meteorological analyses and aircraft and satellite observations. The main dynamical and chemical climatological characteristics of the extratropical UTLS are generally well represented by the models, despite the limited horizontal and vertical resolution. The seasonal cycle of lowermost stratospheric mass is realistic, however with a wide spread in its mean value. A tropopause inversion layer is present in most models, although the maximum in static stability is located too high above the tropopause and is somewhat too weak, as expected from limited model resolution. Similar comments apply to the extratropical tropopause transition layer. The seasonality in lower stratospheric chemical tracers is consistent with the seasonality in the Brewer‐Dobson circulation. Both vertical and meridional tracer gradients are of similar strength to those found in observations. Models that perform less well tend to use a semi‐Lagrangian transport scheme and/or have a very low resolution. Two models, and the multimodel mean, score consistently well on all diagnostics, while seven other models score well on all diagnostics except the seasonal cycle of water vapor. Only four of the models are consistently below average. The lack of tropospheric chemistry in most models limits their evaluation in the upper troposphere. Finally, the UTLS is relatively sparsely sampled by observations, limiting our ability to quantitatively evaluate many aspects of model performance.
    Journal of Geophysical Research. 01/2010; 115(2010-D00M09):1-24.
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    ABSTRACT: The evolution of stratospheric ozone from 1960 to 2100 is examined in simulations from 14 chemistry-climate models, driven by prescribed levels of halogens and greenhouse gases. There is general agreement among the models that total column ozone reached a minimum around year 2000 at all latitudes, projected to be followed by an increase over the first half of the 21st century. In the second half of the 21st century, ozone is projected to continue increasing, level off, or even decrease depending on the latitude. Separation into partial columns above and below 20 hPa reveals that these latitudinal differences are almost completely caused by differences in the model projections of ozone in the lower stratosphere. At all latitudes, upper stratospheric ozone increases throughout the 21st century and is projected to return to 1960 levels well before the end of the century, although there is a spread among models in the dates that ozone returns to specific historical values. We find decreasing halogens and declining upper atmospheric temperatures, driven by increasing greenhouse gases, contribute almost equally to increases in upper stratospheric ozone. In the tropical lower stratosphere, an increase in upwelling causes a steady decrease in ozone through the 21st century, and total column ozone does not return to 1960 levels in most of the models. In contrast, lower stratospheric and total column ozone in middle and high latitudes increases during the 21st century, returning to 1960 levels well before the end of the century in most models.
    Journal of Geophysical Research D: Atmospheres. 01/2010;
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    ABSTRACT: The internal variability and coupling between the stratosphere and troposphere in CCMVal‐2 chemistry‐climate models are evaluated through analysis of the annular mode patterns of variability. Computation of the annular modes in long data sets with secular trends requires refinement of the standard definition of the annular mode, and a more robust procedure that allows for slowly varying trends is established and verified. The spatial and temporal structure of the models’ annular modes is then compared with that of reanalyses. As a whole, the models capture the key features of observed intraseasonal variability, including the sharp vertical gradients in structure between stratosphere and troposphere, the asymmetries in the seasonal cycle between the Northern and Southern hemispheres, and the coupling between the polar stratospheric vortices and tropospheric midlatitude jets. It is also found that the annular mode variability changes little in time throughout simulations of the 21st century. There are, however, both common biases and significant differences in performance in the models. In the troposphere, the annular mode in models is generally too persistent, particularly in the Southern Hemisphere summer, a bias similar to that found in CMIP3 coupled climate models. In the stratosphere, the periods of peak variance and coupling with the troposphere are delayed by about a month in both hemispheres. The relationship between increased variability of the stratosphere and increased persistence in the troposphere suggests that some tropospheric biases may be related to stratospheric biases and that a well‐simulated stratosphere can improve simulation of tropospheric intraseasonal variability.
    Journal of Geophysical Research Atmospheres 01/2010; 115(2010-D00M06):1-15. · 3.44 Impact Factor
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    ABSTRACT: The performance of 18 coupled Chemistry Climate Models (CCMs) in the Tropical Tropopause Layer (TTL) is evaluated using qualitative and quantitative diagnostics. Trends in tropopause quantities in the tropics and the extratropical Upper Troposphere and Lower Stratosphere (UTLS) are analyzed. A quantitative grading methodology for evaluating CCMs is extended to include variability and used to develop four different grades for tropical tropopause temperature and pressure, water vapor and ozone. Four of the 18 models and the multi‐model mean meet quantitative and qualitative standards for reproducing key processes in the TTL. Several diagnostics are performed on a subset of the models analyzing the Tropopause Inversion Layer (TIL), Lagrangian cold point and TTL transit time. Historical decreases in tropical tropopause pressure and decreases in water vapor are simulated, lending confidence to future projections. The models simulate continued decreases in tropopause pressure in the 21st century, along with ∼1K increases per century in cold point tropopause temperature and 0.5–1 ppmv per century increases in water vapor above the tropical tropopause. TTL water vapor increases below the cold point. In two models, these trends are associated with 35% increases in TTL cloud fraction. These changes indicate significant perturbations to TTL processes, specifically to deep convective heating and humidity transport. Ozone in the extratropical lowermost stratosphere has significant and hemispheric asymmetric trends. O3 is projected to increase by nearly 30% due to ozone recovery in the Southern Hemisphere (SH) and due to enhancements in the stratospheric circulation. These UTLS ozone trends may have significant effects in the TTL and the troposphere.
    Journal of Geophysical Research. 01/2010; 115(2010-D00M08):1-22.
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    ABSTRACT: The impact of stratospheric ozone on the tropospheric general circulation of the Southern Hemisphere (SH) is examined with a set of chemistry-climate models participating in the Stratospheric Processes and their Role in Climate (SPARC)/Chemistry-Climate Model Validation project phase 2 (CCMVal-2). Model integrations of both the past and future climates reveal the crucial role of stratospheric ozone in driving SH circulation change: stronger ozone depletion in late spring generally leads to greater poleward displacement and intensification of the tropospheric midlatitude jet, and greater expansion of the SH Hadley cell in the summer. These circulation changes are systematic as poleward displacement of the jet is typically accompanied by intensification of the jet and expansion of the Hadley cell. Overall results are compared with coupled models participating in the Intergovernmental Panel on Climate Change Fourth Assessment Report (IPCC AR4), and possible mechanisms are discussed. While the tropospheric circulation response appears quasi-linearly related to stratospheric ozone changes, the quantitative response to a given forcing varies considerably from one model to another. This scatter partly results from differences in model climatology. It is shown that poleward intensification of the westerly jet is generally stronger in models whose climatological jet is biased toward lower latitudes. This result is discussed in the context of quasi-geostrophic zonal mean dynamics.
    Journal of Geophysical Research. 01/2010; 115(2010-D00M07):1-18.
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    ABSTRACT: The atmospheric response to the 11-year solar cycle is studied using the fully interactive 3-D coupled chemistry-general circulation model LMDz-REPROBUS with a complete seasonal cycle. We will show results concerning a comparison between two series of 20-year runs, one in maximum of activity and the other in minimum. The stratosphere-troposphere system shows partly significant response to a solar cycle enhancement of UV radiation. We show how the changes in stratospheric ozone, temperature and zonal wind are connected.
    Proceedings of the International Astronomical Union 07/2009; 5:350 - 355.
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    ABSTRACT: The representation of the Tropical Tropopause Layer (TTL) in 13 different Chemistry Climate Models (CCMs) designed to represent the stratosphere is analyzed. Simulations for 1960–2005 and 1980–2100 are analyzed. Simulations for 1960–2005 are compared to reanalysis model output. CCMs are able to reproduce the basic structure of the TTL. There is a large (10 K) spread in annual mean tropical cold point tropopause temperatures. CCMs are able to reproduce historical trends in tropopause pressure obtained from reanalysis products. Simulated historical trends in cold point tropopause temperatures are not consistent across models or reanalyses. The pressure of both the tropical tropopause and the level of main convective outflow appear to have decreased (increased altitude) in historical runs as well as in reanalyses. Decreasing pressure trends in the tropical tropopause and level of main convective outflow are also seen in the future. Models consistently predict decreasing tropopause and convective outflow pressure, by several hPa/decade. Tropical cold point temperatures are projected to increase by 0.09 K/decade. Tropopause anomalies are highly orrelated with tropical surface temperature anomalies and with tropopause level ozone anomalies, less so with stratospheric temperature anomalies. Simulated stratospheric water vapor at 90 hPa increases by up to 0.5–1 ppmv by 2100. The result is consistent with the simulated increase in temperature, highlighting the correlation of tropopause temperatures with stratospheric water vapor.
    Atmospheric Chemistry and Physics. 01/2009; 9(2009):1621-1637.
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    ABSTRACT: A case study of a polar stratospheric cloud (PSC) is described using multiwavelength (355, 532, and 1064 nm) lidar measurements performed at the Arctic Lidar Observatory for Middle Atmosphere Research (ALOMAR) on 6 December 2005. Rotational Raman signals at 529 and 530 nm are used to derive a temperature field within the cloud using the rotational Raman technique (RRT). The PSC size distributions are retrieved between 1500 and 2000 UTC through a combination of statistical filtering and best match approaches. Several PSC types were detected between 22 and 26 km during the measurement session. Liquid ternary aerosols are identified before about 1600 and after 1900 UTC typically; their averaged retrieved size distribution parameters and associated errors at the backscatter peak are: No ≈ 1–10 cm−3 (50%), rm ≈ 0.15 μm (20%), and σ ≈ 1.2 (15%). A mode of much larger particles is detected between 1600 and 1900 UTC (No ≈ 0.04 cm−3 (30%), rm ≈ 1.50 μm (15%), and σ ≈ 1.37 (10%). The different PSC types are also identified using standard semiempirical classifications, based on lidar backscatter, temperature, and depolarization. Overall, the characteristics of the retrieved size distributions are consistent with these classifications. They all suggest that these very large particles are certainly nitric acid trihydrate that could have been generated by the strong gravity wave activity visible in the temperature profiles. The results demonstrate that multiwavelength lidar data coupled to both RRT temperatures and our size distribution retrieval can provide useful additional information for identification of PSC types and for direct comparisons with microphysical model simulations.
    Journal of Geophysical Research Atmospheres 01/2009; 114. · 3.44 Impact Factor
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    ABSTRACT: Simulations of the stratosphere from thirteen coupled chemistry-climate models (CCMs) are evaluated to provide guidance for the interpretation of ozone predictions made by the same CCMs. The focus of the evaluation is on how well the fields and processes that are important for determining the ozone distribution are represented in the simulations of the recent past. The core period of the evaluation is from 1980 to 1999 but long-term trends are compared for an extended period (1960–2004). Comparisons of polar high-latitude temperatures show that most CCMs have only small biases in the Northern Hemisphere in winter and spring, but still have cold biases in the Southern Hemisphere spring below 10 hPa. Most CCMs display the correct stratospheric response of polar temperatures to wave forcing in the Northern, but not in the Southern Hemisphere. Global long-term stratospheric temperature trends are in reasonable agreement with satellite and radiosonde observations. Comparisons of simulations of methane, mean age of air, and propagation of the annual cycle in water vapor show a wide spread in the results, indicating differences in transport. However, for around half the models there is reasonable agreement with observations. In these models the mean age of air and the water vapor tape recorder signal are generally better than reported in previous model intercomparisons. Comparisons of the water vapor and inorganic chlorine (Cly) fields also show a large intermodel spread. Differences in tropical water vapor mixing ratios in the lower stratosphere are primarily related to biases in the simulated tropical tropopause temperatures and not transport. The spread in Cly, which is largest in the polar lower stratosphere, appears to be primarily related to transport differences. In general the amplitude and phase of the annual cycle in total ozone is well simulated apart from the southern high latitudes. Most CCMs show reasonable agreement with observed total ozone trends and variability on a global scale, but a greater spread in the ozone trends in polar regions in spring, especially in the Arctic. In conclusion, despite the wide range of skills in representing different processes assessed here, there is sufficient agreement between the majority of the CCMs and the observations that some confidence can be placed in their predictions.
    Journal of Geophysical Research Atmospheres 01/2006; 111(2006-11-23):D22308. · 3.44 Impact Factor
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    ABSTRACT: The NO3 measurement by the GOMOS instrument on board the ENVISAT platform is the first satellite measurements of this species. The simultaneous measurements of O3 and NO2, which are strongly coupled chemically to NO3, allow us to test the self-consistency of the GOMOS measurements of the different species. In this paper, the self-consistency of the nighttime measurements by GOMOS of O3, NO2 and NO3 are tested using chemical data assimilation. Measurements obtained between 25 and 55 km during two distinct periods are assimilated. Analyzed NO3 (i.e., NO3 calculated by the model after assimilation of GOMOS O3 and NO2 data) are then compared to corresponding GOMOS NO3 measurements in correlation plots (GOMOS NO3 versus analyzed NO3). Overall, the differences between the NO3 measurements and corresponding analyzed NO3 are found to be small, about 10% on average. The linear regressions for both periods are also found to be close to the 1-to-1 line with small standard errors. This agreement indicates that O3, NO2 and NO3 GOMOS measurements are self consistent chemically and that there is no substantial bias in GOMOS NO3 data. It also suggests that the nighttime NO3 chemistry is well understood.
    Geophysical Research Letters. 01/2004; 31(10):L10107.
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    ABSTRACT: 1] The Modéle Isentropique de transport Mésoéchelle de l'Ozone Stratosphérique par Advection avec CHIMie (MIMOSA-CHIM) three-dimensional high-resolution chemical transport model has been developed to estimate the contribution of polar ozone destruction to the lower stratosphere ozone budget at midlatitudes. The ability of the model to reproduce the evolution of polar and midlatitude ozone during the 1999/2000 winter is first evaluated by comparisons against lidar and sonde measurements. The modeled potential vorticity (PV) fields are also compared with PV fields derived from ECMWF analyses and the chemical fields of the model are compared with the output of a large-scale chemical transport model in order to highlight the interest of a high-resolution model for resolving fine-scale structures such as polar filaments. A PV-based analysis is performed to estimate the area covered by polar air, vortex, and filaments in the 45°N– 55°N latitude band at 475K and their contribution to ozone loss. The polar air contribution was found to represent usually between 20% and 40% of the total ozone loss in this latitude band but can reach 50% during large vortex intrusions. At 475K, the total chemical ozone loss in nonpolar air between 45°N and 55°N increases from 1% in mid-December to 15% at the end of March. Several chemical ozone tracers are considered to investigate the origin of the ozone loss in nonpolar air. These tracers allow us to quantify the amount of chemical ozone destruction that occurred in the vortex, in the polar filamentary structures, and in the nonpolar air. Until February, the main contributor to the nonpolar ozone loss is in situ destruction at midlatitudes, but the contribution from the ozone destruction in the polar vortex increases steadily during the winter and represents about 50% of the total midlatitude ozone loss in April, after the vortex breakup. The contribution from the ozone destruction within filamentary structures is found to be quasi-negligible as a result of the limited number of filaments. INDEX TERMS: 3334 Meteorology and Atmospheric Dynamics: Middle atmosphere dynamics (0341, 0342); 0341 Atmospheric Composition and Structure: Middle atmosphere—constituent transport and chemistry (3334); 0340 Atmospheric Composition and Structure: Middle atmosphere—composition and chemistry; KEYWORDS: polar filament, midlatitude, ozone loss, irreversible transport, chemical ozone loss Citation:, Influence of polar ozone loss on northern midlatitude regions estimated by a high-resolution chemistry transport model during winter 1999/2000, J. Geophys. Res., 108(D5), 8326, doi:10.1029/2001JD000906, 2003.
    Journal of Geophysical Research. 01/2003; 108.
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    ABSTRACT: 1] We describe a method for assimilating sequentially tracer measurements in isentropic chemistry-transport models (CTMs) of the stratosphere. The parametrisation of the forecast error covariance and its evolution is largely based on simplifications described in Menard and Chang [2000] and Khattatov et al. [2000]. The model used here is a high resolution isentropic advection model which is driven by ECMWF (European Center for Medium range Weather Forcast) meteorological analyses. The assimilation on isentropic surfaces allow us to exploit the well-established correlation between tracer mixing ratio and potential vorticity in the formulation of the forecast error covariance. Multiple 20-day sequential assimilations of MLS (Microwave Limb Sounder onboard UARS satellite) ozone data during an ozone depletion event are performed. c 2 (chi-square) and OmF (observation minus forecast) statistics are used to optimise the assimilation system by adjusting parameters of the error covariance. The quality of the analysis is found to be significantly improved when the strong correlation between ozone and potential vorticity is taken into account.
    Geophysical Research Letters 05/2002; 29(10). · 3.98 Impact Factor

Publication Stats

419 Citations
43.97 Total Impact Points

Institutions

  • 2009–2012
    • UPMC
      Pittsburgh, Pennsylvania, United States
    • Université de Versailles Saint-Quentin
      Versailles, Île-de-France, France
    • Pierre and Marie Curie University - Paris 6
      Lutetia Parisorum, Île-de-France, France
  • 2010
    • LATMOS
      Guyancourt, Île-de-France, France