Letteratura scientifica selezionata sul tema "Troposphère – Dynamique"
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Articoli di riviste sul tema "Troposphère – Dynamique":
1
Caram, Cyril, Sophie Szopa, Anne Cozic, Slimane Bekki, Carlos A. Cuevas e Alfonso Saiz-Lopez. "Sensitivity of tropospheric ozone to halogen chemistry in the chemistry–climate model LMDZ-INCA vNMHC". Geoscientific Model Development 16, n. 14 (18 luglio 2023): 4041–62. http://dx.doi.org/10.5194/gmd-16-4041-2023.
Abstract (sommario):
Abstract. The atmospheric chemistry of halogenated species (Cl, Br, I) participates in the global chemical sink of tropospheric ozone and perturbs the oxidising capacity of the troposphere, notably by influencing the atmospheric lifetime of methane. Global chemistry–climate models are commonly used to assess the global budget of ozone and its sensitivity to emissions of its precursors, as well as to project its long-term evolution. Here, we report on the implementation of tropospheric sources and chemistry of halogens in the chemistry–climate model LMDZ-INCA (Laboratoire de Météorologie Dynamique general circulation model, LMDZ, and Interactions with Chemistry and Aerosols, INCA, version with Non-Methane HydroCarbon chemistry, vNMHC) and evaluate halogen effects on the tropospheric ozone budget. Overall, the results show that the model simulates satisfactorily the impact of halogens on the photo-oxidising system in the troposphere, in particular in the marine boundary layer. To quantify the effects of halogen chemistry in LMDZ-INCA, standard metrics representative of the behaviour of the tropospheric chemical system (Ox, HOx, NOx, CH4 and non-methane volatile organic compounds – NMVOCs) are computed with and without halogens. The addition of tropospheric halogens in the LMDZ-INCA model leads to a decrease of 22 % in the ozone burden, 8 % in OH and 33 % in NOx. Sensitivity simulations show for the first time that the inclusion of halogen chemistry makes ozone more sensitive to perturbations in CH4, NOx and NMVOCs. Consistent with other global model studies, the sensitivity of the tropospheric ozone burden to changes from pre-industrial to present-day emissions is found to be ∼20 % lower when tropospheric halogens are taken into account.
2
Folberth, G. A., D. A. Hauglustaine, J. Lathière e F. Brocheton. "Interactive chemistry in the Laboratoire de Météorologie Dynamique general circulation model: model description and impact analysis of biogenic hydrocarbons on tropospheric chemistry". Atmospheric Chemistry and Physics 6, n. 8 (21 giugno 2006): 2273–319. http://dx.doi.org/10.5194/acp-6-2273-2006.
Abstract (sommario):
Abstract. We present a description and evaluation of LMDz-INCA, a global three-dimensional chemistry-climate model, pertaining to its recently developed NMHC version. In this substantially extended version of the model a comprehensive representation of the photochemistry of non-methane hydrocarbons (NMHC) and volatile organic compounds (VOC) from biogenic, anthropogenic, and biomass-burning sources has been included. The tropospheric annual mean methane (9.2 years) and methylchloroform (5.5 years) chemical lifetimes are well within the range of previous modelling studies and are in excellent agreement with estimates established by means of global observations. The model provides a reasonable simulation of the horizontal and vertical distribution and seasonal cycle of CO and key non-methane VOC, such as acetone, methanol, and formaldehyde as compared to observational data from several ground stations and aircraft campaigns. LMDz-INCA in the NMHC version reproduces tropospheric ozone concentrations fairly well throughout most of the troposphere. The model is applied in several sensitivity studies of the biosphere-atmosphere photochemical feedback. The impact of surface emissions of isoprene, acetone, and methanol is studied. These experiments show a substantial impact of isoprene on tropospheric ozone and carbon monoxide concentrations revealing an increase in surface O3 and CO levels of up to 30 ppbv and 60 ppbv, respectively. Isoprene also appears to significantly impact the global OH distribution resulting in a decrease of the global mean tropospheric OH concentration by approximately 0.7×105 molecules cm-3 or roughly 8% and an increase in the global mean tropospheric methane lifetime by approximately seven months. A global mean ozone net radiative forcing due to the isoprene induced increase in the tropospheric ozone burden of 0.09 W m-2 is found. The key role of isoprene photooxidation in the global tropospheric redistribution of NOx is demonstrated. LMDz-INCA calculates an increase of PAN surface mixing ratios ranging from 75 to 750 pptv and 10 to 250 pptv during northern hemispheric summer and winter, respectively. Acetone and methanol are found to play a significant role in the upper troposphere/lower stratosphere (UT/LS) budget of peroxy radicals. Calculations with LMDz-INCA show an increase in HOx concentrations region of 8 to 15% and 10 to 15% due to methanol and acetone biogenic surface emissions, respectively. The model has been used to estimate the global tropospheric CO budget. A global CO source of 3019 Tg CO yr-1 is estimated. This source divides into a primary source of 1533 Tg CO yr-1 and secondary source of 1489 Tg CO yr-1 deriving from VOC photooxidation. Global VOC-to-CO conversion efficiencies of 90% for methane and between 20 and 45% for individual VOC are calculated by LMDz-INCA.
3
Bellus, Martin, Yong Wang e Florian Meier. "Perturbing Surface Initial Conditions in a Regional Ensemble Prediction System". Monthly Weather Review 144, n. 9 (settembre 2016): 3377–90. http://dx.doi.org/10.1175/mwr-d-16-0038.1.
Abstract (sommario):
Two techniques for perturbing surface initial conditions in the regional ensemble system Aire Limitée Adaptation Dynamique Développement International-Limited Area Ensemble Forecasting (ALADIN-LAEF) are presented and investigated in this paper. The first technique is the noncycling surface breeding (NCSB), which combines short-range surface forecasts driven by perturbed atmospheric forcing and the breeding method for generating the perturbations on surface initial conditions. The second technique, which is currently used in the ALADIN-LAEF operational version, applies an ensemble of surface data assimilations (ESDA) in which the observations are randomly perturbed. Both techniques are evaluated over a two-month period from late spring to summer. The results show that the evaluation is more favorable to ESDA. In general, the ensemble forecasts of the observed near-surface meteorological variables (screen-level variables) of ESDA are more skillful than NCSB, in particular for 2-m temperature they are statistically more consistent and reliable. A slightly better statistical reliability for 2-m relative humidity and 10-m wind has been found as well. This could be attributed to the introduction of surface data assimilation in ESDA, which provides more accurate surface initial conditions. Moreover, the observation perturbation in ESDA helps to better estimate the initial condition uncertainties. For the forecast of precipitation and the upper-air variables in the lower troposphere, both ESDA and NCSB perform very similarly, having neutral impact.
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Van Ginderachter, Michiel, Daan Degrauwe, Stéphane Vannitsem e Piet Termonia. "Simulating model uncertainty of subgrid-scale processes by sampling model errors at convective scales". Nonlinear Processes in Geophysics 27, n. 2 (16 aprile 2020): 187–207. http://dx.doi.org/10.5194/npg-27-187-2020.
Abstract (sommario):
Abstract. Ideally, perturbation schemes in ensemble forecasts should be based on the statistical properties of the model errors. Often, however, the statistical properties of these model errors are unknown. In practice, the perturbations are pragmatically modelled and tuned to maximize the skill of the ensemble forecast. In this paper a general methodology is developed to diagnose the model error, linked to a specific physical process, based on a comparison between a target and a reference model. Here, the reference model is a configuration of the ALADIN (Aire Limitée Adaptation Dynamique Développement International) model with a parameterization of deep convection. This configuration is also run with the deep-convection parameterization scheme switched off, degrading the forecast skill. The model error is then defined as the difference of the energy and mass fluxes between the reference model with scale-aware deep-convection parameterization and the target model without deep-convection parameterization. In the second part of the paper, the diagnosed model-error characteristics are used to stochastically perturb the fluxes of the target model by sampling the model errors from a training period in such a way that the distribution and the vertical and multivariate correlation within a grid column are preserved. By perturbing the fluxes it is guaranteed that the total mass, heat and momentum are conserved. The tests, performed over the period 11–20 April 2009, show that the ensemble system with the stochastic flux perturbations combined with the initial condition perturbations not only outperforms the target ensemble, where deep convection is not parameterized, but for many variables it even performs better than the reference ensemble (with scale-aware deep-convection scheme). The introduction of the stochastic flux perturbations reduces the small-scale erroneous spread while increasing the overall spread, leading to a more skillful ensemble. The impact is largest in the upper troposphere with substantial improvements compared to other state-of-the-art stochastic perturbation schemes. At lower levels the improvements are smaller or neutral, except for temperature where the forecast skill is degraded.
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Zhou, Tianjun, Rucong Yu, Jie Zhang, Helge Drange, Christophe Cassou, Clara Deser, Daniel L. R. Hodson et al. "Why the Western Pacific Subtropical High Has Extended Westward since the Late 1970s". Journal of Climate 22, n. 8 (15 aprile 2009): 2199–215. http://dx.doi.org/10.1175/2008jcli2527.1.
Abstract (sommario):
Abstract The western Pacific subtropical high (WPSH) is closely related to Asian climate. Previous examination of changes in the WPSH found a westward extension since the late 1970s, which has contributed to the interdecadal transition of East Asian climate. The reason for the westward extension is unknown, however. The present study suggests that this significant change of WPSH is partly due to the atmosphere’s response to the observed Indian Ocean–western Pacific (IWP) warming. Coordinated by a European Union’s Sixth Framework Programme, Understanding the Dynamics of the Coupled Climate System (DYNAMITE), five AGCMs were forced by identical idealized sea surface temperature patterns representative of the IWP warming and cooling. The results of these numerical experiments suggest that the negative heating in the central and eastern tropical Pacific and increased convective heating in the equatorial Indian Ocean/Maritime Continent associated with IWP warming are in favor of the westward extension of WPSH. The SST changes in IWP influences the Walker circulation, with a subsequent reduction of convections in the tropical central and eastern Pacific, which then forces an ENSO/Gill-type response that modulates the WPSH. The monsoon diabatic heating mechanism proposed by Rodwell and Hoskins plays a secondary reinforcing role in the westward extension of WPSH. The low-level equatorial flank of WPSH is interpreted as a Kelvin response to monsoon condensational heating, while the intensified poleward flow along the western flank of WPSH is in accord with Sverdrup vorticity balance. The IWP warming has led to an expansion of the South Asian high in the upper troposphere, as seen in the reanalysis.
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Behrendt, Andreas, Volker Wulfmeyer, Thorsten Schaberl, Hans-Stefan Bauer, Christoph Kiemle, Gerhard Ehret, Cyrille Flamant et al. "Intercomparison of Water Vapor Data Measured with Lidar during IHOP_2002. Part II: Airborne-to-Airborne Systems". Journal of Atmospheric and Oceanic Technology 24, n. 1 (1 gennaio 2007): 22–39. http://dx.doi.org/10.1175/jtech1925.1.
Abstract (sommario):
Abstract The dataset of the International H2O Project (IHOP_2002) gives the first opportunity for direct intercomparisons of airborne water vapor lidar systems and allows very important conclusions to be drawn for future field campaigns. Three airborne differential absorption lidar (DIAL) systems were operated simultaneously during some IHOP_2002 missions: the DIAL of Deutsches Zentrum für Luft- und Raumfahrt (DLR), the Lidar Atmospheric Sensing Experiment (LASE) of the National Aeronautics and Space Administration (NASA) Langley Research Center, and the Lidar Embarque pour l’etude des Aerosols et des Nuages de l’interaction Dynamique Rayonnement et du cycle de l’Eau (LEANDRE II) of the Centre National de la Recherche Scientifique (CNRS). Data of one formation flight with DLR DIAL and LEANDRE II were investigated, which consists of 54 independent profiles of the two instruments measured with 10-s temporal average. For the height range of 1.14–1.64 km above sea level, a bias of (−0.41 ± 0.16) g kg−1 or −7.9% ± 3.1% was found for DLR DIAL compared to LEANDRE II (LEANDRE II drier) as well as root-mean-square (RMS) deviations of (0.87 ± 0.18) g kg−1 or 16.9% ± 3.5%. With these results, relative bias values of −9.3%, −1.5%, +2.7%, and +8.1% result for LEANDRE II, DLR DIAL, the scanning Raman lidar (SRL), and LASE, respectively, using the mutual bias values determined in Part I for the latter three sensors. From the three possible profile-to-profile intercomparisons between DLR DIAL and LASE, one case cannot provide information on the system performances due to very large inhomogeneity of the atmospheric water vapor field, while one of the two remaining two cases showed a difference of −4.6% in the height range of 1.4–3.0 km and the other of −25% in 1.3–3.8 km (in both cases DLR DIAL was drier than LASE). The airborne-to-airborne comparisons showed that if airborne water vapor lidars are to be validated down to an accuracy of better than 5% in the lower troposphere, the atmospheric variability of water vapor has to be taken into account down to scales of less than a kilometer unless a sufficiently large number of intercomparison cases is available to derive statistically solid biases and RMS deviations. In conclusion, the overall biases between the water vapor data of all three airborne lidar systems operated during IHOP_2002 are smaller than 10% in the present stage of data evaluation, which confirms the previous estimates of the instrumental accuracies for all the systems.
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Horvath, Kristian, Alica Bajić e Stjepan Ivatek-Šahdan. "Dynamical Downscaling of Wind Speed in Complex Terrain Prone To Bora-Type Flows". Journal of Applied Meteorology and Climatology 50, n. 8 (agosto 2011): 1676–91. http://dx.doi.org/10.1175/2011jamc2638.1.
Abstract (sommario):
AbstractThe results of numerically modeled wind speed climate, a primary component of wind energy resource assessment in the complex terrain of Croatia, are given. For that purpose, dynamical downscaling of 10 yr (1992–2001) of the 40-yr ECMWF Re-Analysis (ERA-40) was performed to 8-km horizontal grid spacing with the use of a spectral, prognostic full-physics model Aire Limitée Adaptation Dynamique Développement International (ALADIN; the “ALHR” version). Then modeled data with a 60-min frequency were refined to 2-km horizontal grid spacing with a simplified and cost-effective model version, the so-called dynamical adaptation (DADA). The statistical verification of ERA-40-, ALHR-, and DADA-modeled wind speed on the basis of data from measurement stations representing different regions of Croatia suggests that downscaling was successful and that model accuracy generally improves as horizontal resolution is increased. The areas of the highest mean wind speeds correspond well to locations of frequent and strong bora flow as well as to the prominent mountain peaks. The best results are achieved with DADA and contain bias of 1% of the mean wind speed for eastern Croatia while reaching 10% for complex coastal terrain, mainly because of underestimation of the strongest winds. Root-mean-square errors for DADA are significantly smaller for flat terrain than for complex terrain, with relative values close to 12% of the mean wind speed regardless of the station location. Spectral analyses suggest that the shape of the kinetic energy spectra generally relaxes from k−3 at the upper troposphere to the shape of orographic spectra near the surface and shows no seasonal variability. Apart from the buildup of energy on smaller scales of motions, it is shown that mesoscale simulations contain a considerable amount of energy related to near-surface and mostly divergent meso-β-scale (20–200 km) motions. Spectral decomposition of measured and modeled data in temporal space indicates a reasonable performance of all model datasets in simulating the primary maximum of spectral power related to synoptic and larger-than-diurnal mesoscale motions, with somewhat increased accuracy of mesoscale model data. The primary improvement of dynamical adaptation was achieved for cross-mountain winds, whereas mixed results were found for along-mountain wind directions. Secondary diurnal and tertiary semidiurnal maxima are significantly better simulated with the mesoscale model for coastal stations but are somewhat more erroneous for the continental station. The mesoscale model data underestimate the spectral power of motions with less-than-semidiurnal periods.
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Massart, S., A. Agusti-Panareda, I. Aben, A. Butz, F. Chevallier, C. Crevoisier, R. Engelen, C. Frankenberg e O. Hasekamp. "Assimilation of atmospheric methane products in the MACC-II system: from SCIAMACHY to TANSO and IASI". Atmospheric Chemistry and Physics Discussions 14, n. 2 (27 gennaio 2014): 2553–99. http://dx.doi.org/10.5194/acpd-14-2553-2014.
Abstract (sommario):
Abstract. The Monitoring Atmospheric Composition and Climate Interim Implementation (MACC-II) delayed-mode (DM) system has been producing an atmospheric methane (CH4) analysis 6 months behind real time since June 2009. This analysis used to rely on the assimilation of the CH4 product from the SCanning Imaging Absorption spectroMeter for Atmospheric CHartographY (SCIAMACHY) instrument on board Envisat. Recently the \\textit{Laboratoire de Météorologie Dynamique} (LMD) CH4 products from the Infrared Atmospheric Sounding Interferometer (IASI) and the SRON Netherlands Institute for Space Research CH4 products from the Thermal And Near-infrared Sensor for carbon Observation (TANSO) were added to the DM system. With the loss of Envisat in April 2012, the DM system has to now rely on the assimilation of methane data from TANSO and IASI. This paper documents the impact of this change in the observing system on the methane tropospheric analysis. It is based on four experiments: one free run and three analyses from respectively the assimilation of SCIAMACHY, TANSO and a combination of TANSO and IASI CH4 products in the MACC-II system. The period between December 2010 and April 2012 is studied. This corresponds to a period during which the performance of SCIAMACHY was deteriorating. The SCIAMACHY experiment globally underestimates the tropospheric methane by 35 part per billion (ppb) compared to the HIAPER Pole-to-Pole Observations (HIPPO) data and the methane column by 23 ppb compared the Total Carbon Column Observing Network (TCCON) data, when the global bias of the free run against the same HIPPO and TCCON data is respectively −5 ppb and 4 ppb. The assimilated TANSO product changed in October 2011 from version v.1 to version v.2.0. The analysis of version v.1 globally underestimates the tropospheric methane by 18 ppb compared to the HIPPO data and the column by 11 ppb compared to the TCCON data. In contrast, the analysis of version v.2.0 globally overestimates the column by 10 ppb. When the high density IASI data are added in the tropical region between 30° N and 30° S, the resulting analysis is slightly less biased in the troposphere than the TANSO analysis when compared to the HIPPO data. In the meantime, this IASI plus TANSO analysis presents the worst correlation with the HIPPO data. In terms of column, the addition of the IASI data to the version v.2.0 of the TANSO data has a significant impact, mainly over extratropical regions, reducing the global bias to 6 ppb. The analysis based on the assimilation of the combination of TANSO and IASI products as well as the SCIAMACHY analysis should nevertheless be used with caution when looking at the seasonal cycle or inter-hemispheric gradient because of the unavailability of the measurements over large regions during the local winter period.
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Milcareck, Gwenaël, Sandrine Guerlet, Franck Montmessin, Aymeric Spiga, Jérémy Leconte, Ehouarn Millour, Noé Clément et al. "Radiative-convective models of the atmospheres of Uranus and Neptune: Heating sources and seasonal effects". Astronomy & Astrophysics, 18 aprile 2024. http://dx.doi.org/10.1051/0004-6361/202348987.
Abstract (sommario):
The observations made during the Voyager 2 flyby have shown that the stratosphere of Uranus and that of Neptune are warmer than expected by previous models. In addition, no seasonal variability of the thermal structure has been observed on Uranus since Voyager 2 era and significant subseasonal variations have been revealed on Neptune. In this paper, we evaluate different realistic heat sources that can induce sufficient heating to warm the atmosphere of these planets and we estimate the seasonal effects on the thermal structure. The seasonal radiative-convective model developed by the Laboratoire de Météorologie Dynamique was used to reproduce the thermal structure of these planets. Three hypotheses for the heating sources were explored separately: aerosol layers, a higher methane mole fraction, and thermospheric conduction. Our modelling indicates that aerosols with plausible scattering properties can produce the requisite heating for Uranus, but not for Neptune. Alternatively, greater stratospheric methane abundances can provide the missing heating on both planets, but the large values needed are inconsistent with current observational constraints. In contrast, adding thermospheric conduction cannot warm the stratosphere of both planets alone. The combination of these heat sources is also investigated. In the upper troposphere of both planets, the meridional thermal structures produced by our model are found inconsistent with those retrieved from Voyager 2/IRIS data. Furthermore, our models predict seasonal variations should exist within the stratospheres of both planets while observations showed that Uranus seems to be invariant to meridional contrasts and only subseasonal temperature trends are visible on Neptune. However, a warm south pole is seen in our simulations of Neptune as observed since 2003.
Tesi sul tema "Troposphère – Dynamique":
1
Leroy, Céline. "Analyse dynamique de la pollution de l'air dans la troposphère". Littoral, 2008. http://www.theses.fr/2008DUNK0206.
Abstract (sommario):
La caractérisation et la prévision des épisodes de pollution de l’air nécessitent une approche à la fois chimique et météorologique. Dans ce travail, nous nous sommes donc attachés à mettre en évidence les relations entre les phénomènes météorologiques et la pollution de l’air. Pour cela, nous avons mis en œuvre, dans l’agglomération dunkerquoise, une campagne de mesures de six mois, associant des mesures météorologiques, micro-météorologiques et de composés de type BTEX (Benzène, Toluène, Ethyl-Benzène et Xylènes). Des mesures de flux turbulents ont permis d’évaluer la capacité dispersive de l’atmosphère lors de périodes anticycloniques, dépressionnaires, de passages de front et d’épisodes de brises côtières. Cette étude a montré en particulier le rôle majeur de la brise, à l’origine des plus importants épisodes de pollution de la campagne. Afin d’appréhender l’aspect dynamique tridimensionnel de la brise et par conséquent, le devenir des polluants en altitude, nous avons caractérisé la structure d’un épisode de brise à partir d’instruments de télédétection optique et acoustique et de simulations numériques. L’étude de la pollution de fond a été menée à proximité du site de surveillance du Pic du Midi de Bigorre (PDM) dans les Pyrénées. Des études climatologiques précédentes ont révélé un comportement atypique du cycle d’ozone en période estivale, se traduisant par une diminution d’ozone en milieu de journée. A l’aide d’un lidar à absorption différentielle, nous avons pu mesurer au voisinage du PDM les profils verticaux de l’ozone et du coefficient d’extinction afin d’étudier in situ le rôle des phénomènes météorologiques locaux de brises de pentesThe characterization and the forecast of air pollution episodes require a combined chemical and weather approach. So, in this work the relations between the meteorological situation and the air pollution. Thereby, a field campaign associating weather, micrometeorological and BTEX (Benzene, Toluene, Ethyl-Benzene and Xylenes) compounds was carried out during six months in Dunkirk. Measurements of turbulent flows were used to evaluate the dispersive capacity of the atmosphere during anticyclonic and depressionary periods, front passages and sea breeze episodes. This study showed in particular that the sea breeze was responsible of the most important pollution episodes of the measurements period. In order to apprehend the three-dimensional dynamic aspect of the breeze and consequently, the pollution behaviour in altitude, the structure of a sea breeze episode was characterized from optical and acoustic teledetection instruments and numerical simulations. The study of the background pollution occured in the neighbouring of the monitoring site of the “Pic du Midi de Bigorre” (PDM) in the Pyrenees (France). Previous studies revealed an atypical behavior of the ozone cycle in summer period, resulting in a decline of ozone in the middle of day. In order to study experimentally the role of the local weather phenomena, the vertical profiles of the ozone and of the extinction coefficient were measured with a differential absorption lidar in the vicinity of the PDM
2
Radola, Bastien. "Modélisation à l'échelle moléculaire des aérosols carbonés dans la troposphère". Thesis, Bourgogne Franche-Comté, 2017. http://www.theses.fr/2017UBFCD080/document.
Abstract (sommario):
Dans ce travail de thèse, des méthodes de simulation numérique ont été utilisées afin de modéliser, à l’échelle moléculaire,l’interaction entre des aérosols carbonés et diverses molécules de l’atmosphère.L’objectif était de caractériser les propriétés physico-chimiques de ces aérosols, qui jouent un rôle majeur dans le climat, en particulier via leur capacité à former des noyaux de condensation pour les molécules d’eau. En premier lieu, les techniques de la dynamique moléculaire ont été appliquées à la détermination de l’organisation d’agrégats d’acide carboxylique sur lesquels sont adsorbées des molécules d’eau. Les résultats montrent une influence à la fois de la température, du taux d’humidité et du type d’acide considéré sur le comportement global des agrégats. Par contre, il a été montré qu’un mélange binaire d’acides n’a que peu d’influence sur ce comportement. En second lieu, des techniques de simulation moléculaires quantiques, à la fois statiques et dynamiques, ont été appliquées à l’étude de la chloration de surfaces de suie, modélisées par de grands HAP, ainsi qu’à la caractérisation de leur affinité pour les molécules d’eau. Les résultats ont montré une forte propension de Cl, Cl2 et HCl à former des HAP chlorés à la faveur de la présence de défauts structurels. Ces structures chlorées présentent une forte hydrophilicité, ce qui pourrait expliquer la nature fortement hygroscopique de suies émises lors d’incendies industrielsIn this PhD work, molecular simulation methods have been used in order to model, at the molecular scale, the interaction between carbonaceous aerosols andvarious atmospheric species. The aim wasto characterize the physico-chemical properties of these aerosols, which play a major role in climate forcing, in particular through their ability to act as cloud condensation nuclei.First, molecular dynamics techniques have been applied to determine the structure of carboxylic acid aggregates on which water molecules are adsorbed. The results of our simulations show an influence of the temperature, of the humidity and of the type of carboxylic acid considered on the global behavior of the aggregates. By contrast,a mixture of different types of acid molecules has no influence on this behavior. Secondly, quantum molecular simulation techniques have been applied to study the chlorination of soot surfaces, modeled by large PAHs, and their behavior with respect to water molecules adsorption. The results show a strong propensity of Cl, Cl2and HCl species to form chlorinated PAHsthanks to the presence of structural defects.These chlorinated structures show as trong hydrophilicity, which may explain the strong hygroscopic nature of soots emitted by industrial fires
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Canneaux, Sébastien. "Etude théorique de processus atmosphériques : réaction du radical OH avec l'acétone et capture d'un composé organique volatil par une goutte d'eau : thèse pour le doctorat en sciences spécialité Chimie Informatique et Théorique". Reims, 2004. http://theses.univ-reims.fr/exl-doc/GED00000053.pdf.
Abstract (sommario):
"La pollution de l'air devient de plus en plus un sujet d'actualité. Il est devenu nécessaire de comprendre les causes et les conséquences de cette pollution. Ce travail de thèse s'intègre totalement dans cette thématique. Une introduction dresse un tableau des principaux processus atmosphériques, et des méthodes de calculs quantiques ou classiques utilisées. Ce travail de thèse comporte tout d'abord une contribution à la réalisation du logiciel KISTHEP pour le calcul de propriétés thermodynamiques, à partir de données issues de calculs ab initio. Ensuite, une étude concernant une des voies de dégradation atmosphérique de l'acétone (réaction avec le radical OH) est présentée. Cette étude a pour but de contribuer à la réalisation d'un modèle cinétique impliquant un grand nombre de processus réactionnels couplés. Le comportement " non-Arrhénius " de cette réaction laissait supposer la concurrence de plusieurs voies de dégradation. Enfin dans une dernière partie, une étude concernant la capture de Composés Organiques Volatils par une goutte d'eau a été effectuée. La présence de gouttes d'eau troposphériques entraîne une chimie de type multiphasique. Cette chimie est encore mal connue. Ce travail a consisté à importer et à tester les logiciels nécessaires au calcul du coefficient ''d'accommodation'' massique"The air pollution becomes more and more a topical question. It is now necessary to understand the causes and the consequences of this pollution. This PhD's work becomes integrated in this filed. An introduction shows the main atmospheric processes, and quantum or classical calculation methods which are used. First, this PhD's work includes a contribution to the writting of the KISTHEP software for thermodynamic properties calculations, which are computed from ab initio calculations. Then, a study concerning one of the acetone atmospheric decomposition pathway (reaction with the OH radical) is presented. The purpose of this study is to contribute to the development of a kinetic model implying a great number of coupled reactional processes. The " non-Arrhenius " behaviour of this reaction suggested the competition of several degradation pathways. Finally in a last part, a study concerning the uptake of Volatil Organic Compounds by a water droplet was carried out. The presence of water droplets in the troposphere involves a multiphasic chemistry. This chemistry is still badly known. This work consisted in importing and testing the softwares necessary to the calculation of mass accommodation coefficient
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Donnadille, Jérôme. "Dynamique d'altitude dans un cas de cyclogenèse au Nord du courant-jet polaire pendant Fastex : étude diagnostique et numérique". Toulouse 3, 2000. http://www.theses.fr/2000TOU30164.
5
Morel, Béatrice. "Impact de la troposphère sur le transport isentropique dans la stratosphère via les ondes planétaires de Rossby". Paris 6, 2004. http://www.theses.fr/2004PA066566.
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Semane, Noureddine. "Etude par simulation et assimilation de la composition chimique et des échanges dans la haute troposphère-basse stratosphère". Toulouse 3, 2008. http://thesesups.ups-tlse.fr/893/.
Abstract (sommario):
Comme en météorologie et en océanographie, l'assimilation de données permet de combiner de façon optimale les modèles décrivant l'évolution de la composition chimique et la variété des observations disponibles. Elle est utilisée dans ce travail pour caractériser les distributions de l'ozone (O3) et du protoxyde d'azote (N2O) dans le but d'en tirer une information sur les phénomènes couplés de chimie et de dynamique dans la région de la haute troposphère et basse stratosphère (UTLS). Ce travail s'appuie sur deux outils complémentaires à Météo-France : l'un est basé sur le modèle global de chimie-transport MOCAGE et le logiciel d'assimilation multi-méthodes PALM du CERFACS exploité pour mettre en oeuvre une méthode d'assimilation variationnelle 3D-FGAT; l'autre est une extension du système opérationnel d'assimilation météorologique ARPEGE utilisant la méthode variationnelle incrémentale 4D-Var. D'une part, les champs assimilés (analyses de MOCAGE-PALM) sont utilisés pour l'étude de la chimie et la dynamique stratosphérique polaire ainsi que pour le suivi du transport méridien et des échanges entre la troposphère et la stratosphère. D'autre part, l'assimilation couplée chimie-dynamique dans ARPEGE est utilisée pour évaluer l'impact dynamique des observations d'ozone dans la région de l'UTLSAs in meteorology and oceanography, data assimilation combines in an optimal way chemistry-transport models and observations. In this work, the assimilation of remote-sensing chemical measurements of ozone (O3) and nitrous oxide (N2O) aims at better characterizing their three-dimensional distributions. The objective is to get insight into the coupled chemical and dynamical phenomena in the upper troposphere - lower stratosphere (UTLS). This work uses two complementary tools in Météo-France: one is based on the three dimensional chemistry and transport model MOCAGE and the PALM software of CERFACS using the 3D-FGAT variational technique; the other is an extension of the operational suite of the numerical weather prediction ARPEGE using the 4D-Var variational technique. On one hand, the assimilated fields (MOCAGE-PALM analyses) are used for the study of the polar stratospheric chemistry and dynamics and also for the meridional transport and stratosphere-troposphere exchanges. On the other hand, the chemistry-dynamics coupled assimilation in ARPEGE is used to assess the dynamical impact of ozone observation in the UTLS region
7
Augustin, Patrick. "Analyse par lidar de la dynamique spatiotemporelle de la basse troposphère au cours d'évènements météorologiques locaux : impact sur la qualité de l'air". Littoral, 2004. http://www.theses.fr/2004DUNK0131.
Abstract (sommario):
Les circulations locales des masses d'air jouent un rôle primordial sur la qualité de l'air en zone côtière, urbaine et industrielle. La compréhension de la dynamique de la basse troposphère est nécessaire à la prévision des épisodes de pollution atmosphérique. Dans ce contexte, la combinaison de dispositifs de télédétection et de stations de mesure au sol, apporte une meilleure compréhension de la structure et de la dynamique de la basse troposphère au cours d'évènements météorologiques locaux. La campagne ESCOMPTE a pu documenter les émissions polluantes, la dynamique et la chimie de l'atmosphère de la région de Marseille-Berre afin de tester et de valider les modèles de pollution, en les confrontant aux données expérimentales au sol, aéroportées et par télédétection (lidar UV et IR, radar UHF, sodar). Le lidar de l'Université du Littoral-Côte d'Opale a mesuré la distribution verticale de l'ozone et de l'extinction à proximité de Marseille, zone soumise aux influences de la côte, du relief et de la zone urbaine dense. L'analyse de la structure fine de la stratification complexe observée au cours d'épisodes de pollution photochimique, a mis en évidence un mécanisme de confrontation de brises déterminant pour la couche limite urbaine et le transport des polluants. Dans le cas de la zone littorale fortement industrialisée de la région Nord-Pas-de-Calais, l'analyse de la dynamique de la basse troposphère par le lidar UV, un sodar et des stations de mesure au sol, au cours d'évènements de brise de mer, a permis de déterminer de manière fine la structure verticale de la brise, son évolution temporelle ainsi que son impact sur la dispersion horizontale et verticale des polluantsThe circulations of local air masses play a primordial role on the air quality in coastal, urban and industrial areas. The understanding of the lower troposphere dynamic is necessary to predict atmospheric pollution events. In this context, the combination of remote sensing devices aund ground stations gives a better understanding of the structure and dynamic of the lower troposphere during local meteorological events. The ESCOMPTE campaign was able to characterise polluants emission, dynamic and the atmospheric chemistry composition of Marseille-Berre region in order to test and validate photochemical models by the comparison of experimental data set obtained at ground level, from airborne measurement platform and by ground based remote sensing devices ( UV and IR lidar, UHF radar, sodar). The lidar of the University du Littoral-Côte d'Opale measured the vertical distribution of ozone and extinction coefficient near Marseille which is influenced by the coastline, the relief and the dense urban area. The analysis of the fine structure of the complex stratification observedduring photochemical pollution events, highlighted the importance of the confrontation between the sea breezes, influencing the urban boundary layer pollutant transport. The sea breeze of the highly industrialised coastline of the Nord-Pas-de-Calais region was characterised by the use of the UV lidar, a sodar and ground based measurements. This permitted the determination of the sharp vertical structure and the temporal evolution of the sea breeze demonstrating its influence on the vertical and horizontal pollution dispersion
8
Boissinot, Alexandre. "Modélisation de la dynamique atmosphérique de Jupiter". Electronic Thesis or Diss., Sorbonne université, 2021. http://www.theses.fr/2021SORUS075.
Abstract (sommario):
Jupiter possède une atmosphère extrêmement dynamique caractérisée par des courants-jets alternés, une activité convective intense et un jet équatorial en super-rotation : autant de phénomènes dont les mécanismes de formation restent mal connus. Dans cette thèse nous cherchons à mieux cerner ces mécanismes grâce à la modélisation numérique de la couche météorologique de Jupiter. Pour cela nous utilisons le modèle global de climat DYNAMICO-giant qui a permis pour la première fois de simuler l'écoulement atmosphérique à haute résolution spatiale tout en le forçant avec un transfert radiatif réaliste. Afin d'enrichir la représentation des forçages de l'écoulement dans notre modèle, nous avons adapté le "modèle du thermique", une paramétrisation terrestre de la convection humide, au cas de Jupiter. Nos simulations reproduisent alors spontanément des caractéristiques essentielles de l'atmosphère de Jupiter y compris des jets alternés, un écoulement zonostrophique et une cascade inverse d'énergie traduisant le forçage des jets par la turbulence de moyenne échelle. En revanche, la simulation d'un jet équatorial en super-rotation n'est pas systématique et semble nécessiter la présence d'une activité convective suffisamment humide. Les résultats optimaux sont obtenus pour une abondance atmosphérique en eau de Jupiter proche de celle mesurée récemment par la mission JunoThe extremely dynamic atmosphere of Jupiter is characterised by alternated jets, a strong convective activity and an equatorial super-rotation whose formation mechanisms are poorly understood. In this thesis, we adopt a numerical modelling approach of the jovian weather layer to investigate those formation mechanisms. We use the global climate model DYNAMICO-giant which allows for simulating the atmospheric flow at high resolution with a realistic radiative transfer. In order to improve our model by way of more realistic forcings of the flow, we adapted the "thermal plume model", a terrestrial parametrization of the moist convection, to Jupiter's atmosphere. Thus our simulations recreate spontaneously some of the most essential features of the jovian atmosphere such as alternated jets, the zonostrophic regime of the flow and an inverse cascade of energy which shows jets forcing by the mesoscale turbulence. On the other hand, an equatorial superrotation is not systematically reproduced and seems to require a sufficiently high water atmospheric abundance. Optimal results are obtained for a jovian atmospheric abundance of water close to the one which was measured by the Juno mission
9
Vancassel, Xavier. "Modélisation microphysique de la formation et de l'évolution d'aérosols et de leurs précurseurs dans les sillages d'avions". Université Louis Pasteur (Strasbourg) (1971-2008), 2003. http://www.theses.fr/2003STR13023.
Abstract (sommario):
L'aviation civile connaît depuis maintenant plusieurs années et principalement dans les pays développés une croissance hors normes. Celle-ci s'accompagne malheureusement d'une augmentation des nuisances associées, dont parmi les plus préoccupantes, les émissions qualifiées de "polluantes". L'avion comme tout véhicule propulsé par un système à combustion émet des résidus divers tels que du dioxyde de carbone, des oxydes d'azote et de soufre, de l'eau etc. L'intérêt porté à ces émissions gazeuses, notamment dans le cadre du médiatique "effet de serre" tend pourtant à masquer des conséquences moins directes, comme les effets potentiels des aérosols formés dans les panaches (les traînées de condensation par exemple). Les basses températures rencontrées aux altitudes typiques de vol provoquent effectivement une condensation rapide de certaines espèces en phase gazeuse qui, dans un panache en expansion, sont susceptibles de former de nouvelles particules ayant potentiellement un impact chimique et radiatif susceptible de bouleverser l'équilibre local de la basse stratosphère et de la haute troposphère. Afin de déterminer les caractéristiques de ces particules et d'en favoriser les prédictions, les multiples processus de formation et d'évolution d'aérosols (nucléation, croissance etc. ) ont été considérés dans un modèle numérique, basé sur des mécanismes de collision. Le système étudié a été simplifié au cas d'un mélange binaire gazeux formé d'eau, d'acide sulfurique et d'un aérosol primaire (suies). Le modèle a ainsi été appliqué aux panaches d'avions réels (le Concorde par exemple) mais aussi à une simple chambre de combustion montée sur un banc d'essai expérimental. Les résultats, provenant notamment de nombreuses études de sensibilité, devraient permettre d'une part d'améliorer notre compréhension des phénomènes microphysiques et d'autre part de contribuer à établir des corrélations entre la nature des émissions aériennes et leurs impacts sur l'équilibre atmosphériqueCivil aviation has known for years and mainly in the developed countries an exceptional growth. This one has unfortunately been followed by an increase in the associated harmful effects, especially polluting emissions. Aircraft as any vehicle propelled by a system with combustion emits various residues such as carbon dioxide, nitrogen and sulphur oxides, water etc. The main interest carried to these gas emissions, in particular within the framework of "the greenhouse effect" studies tends to mask less direct consequences, in particular the potential effects of the aerosols formed in plumes. The low temperatures reached at typical altitudes of flight (approximately 10000 m) cause indeed a fast condensation of certain species in gas phase which, in an expanding plume, are likely to form new particles having potentially chemical and radiative impacts which could modify the stratospheric equilibrium. In order to determine the features of these particles (size distribution, concentration etc. ) and to make predictions, the main processes of formation and evolution of aerosols (nucleation, growth etc. ) have been considered in a model, based on collision mechanisms. The system we have studied has been simplified by considering a gas phase water and sulphuric acid binary mixture and a primary aerosol (soot particles). The model has thus been applied to real aircraft plumes (Concorde for instance) but also to a combustion chamber on a test rig. The results, coming in particular from many sensitivity studies, should improve our understanding of the microphysical processes occurring in a plume and should also make us contribute to establish correlations between aircraft emissions and their impacts on the atmospheric equilibrium
10
Charnay, Benjamin. "Dynamique troposphérique et évolution climatique de Titan et de la Terre primitive". Electronic Thesis or Diss., Paris 6, 2014. http://www.theses.fr/2014PA066034.
Abstract (sommario):
Cette thèse porte sur l'étude des atmosphères de Titan et de la Terre primitive avec des modèles de circulation générale (GCM). Tout d'abord, j'ai analysé la structure thermique et la dynamique de la basse troposphère de Titan. Cette étude a abouti à une caractérisation complète de la couche limite et a révélé l'existence d'une circulation de couche limite, qui impacte tous les aspects de la météorologie titanienne (régimes de vents, ondes, formation des dunes et des nuages, échanges de moment cinétique et superrotation). A partir de cette analyse, j'ai proposé une nouvelle hypothèse pour expliquer l'orientation vers l'est des dunes de Titan grâce à un couplage entre les orages tropicaux et la superrotation. Ceci a été validé par des simulations méso-échelles et a permis de proposer un schéma global expliquant la formation des dunes et leurs différentes caractéristiques. J'ai ensuite participé au développement d'un GCM générique, conçu pour étudier tout type d'atmosphère. Je l'ai appliqué aux paléoclimats de Titan pour simuler une période où l'atmosphère a pu être dépourvue de méthane. Dans ce cas, le climat devait être différent d'aujourd'hui avec potentiellement des conséquences géologiques fondamentales notamment pour l'érosion et l'âge de la surface. Finalement, j'ai appliqué ce GCM générique au cas de la Terre primitive. J'ai montré que, malgré un soleil moins lumineux qu'aujourd'hui et des quantités de gaz à effet de serre contraintes par les archives minéralogiques, le climat de la Terre Archéenne a pu être tempérée. En particulier, grâce à une rétro-action nuageuse, la Terre aurait pu éviter une glaciation globale et rester propice au développement de la vieThis thesis focuses on the study of the atmospheres of Titan and the early Earth with Global Climate Models (GCM). First, I analysed the thermal structure and the dynamics of Titan's lower troposphere. This analysis allowed a full caracterization of the planetary boundary layer and revealed the existence of a boundary layer circulation which impacts every aspect of Titan's weather (wind patterns, atmospheric waves, dune and cloud formation, exchange of momentum with the surface, and development of the superrotation). Thanks to this study, I proposed a new hypothesis to explain the eastward orientation of Titan's dunes that implies a coupling between tropical storms and the superrotation. This has been validated with mesoscale simulations and provided a general framework to explain Titan's dune formation and features. Then, I participated to the development of a generic GCM, designed to study any kind of atmosphere. I applied it to Titan's paleoclimates, when the atmosphere was depleted of methane. In such a case, the climate should have been different from today, with potentially fundamental geological consequences, in particular for the erosion and the age of the surface. Finally, I applied this GCM to the case of the early Earth using greenhouse gas abundances constrained by mineralogical data. I showed that despite a weaker solar insolation, the Archean Earth's climate may have been temperate. In particular, the Earth may have avoided a full glaciation and remained suitable for the development of life thanks to cloud feedback, even assuming a amount of CO2 just a little larger than today