Publications

2016

• Evaluation des émissions et de la modélisation de la qualité de l'air sur Beyrouth et le Liban
  
  • Abdallah Charbel
  , 2016. Face aux problèmes sanitaires et environnementaux liés à la pollution atmosphérique au Liban, les études se multiplient pour permettre une bonne compréhension de la situation, dont des mesures de la qualité de l’air et des études sur les émissions de polluants et sur la modélisation des concentrations dans l’atmosphère à l’aide du modèle de chimie transport (CTM) de WRF/Polyphemus. Pour modéliser la qualité de l’air au Liban, les études précédentes se sont heurtées à différentes difficultés dont : une surestimation des concentrations d’ozone d’un facteur 2 dans les résultats de la modélisation WRF/Polyphemus pour l’été 2012, un profil d’émission des COV issus du transport routier différent de ceux que l’on trouve dans les pays développés. De cela dérivent les objectifs de cette thèse : améliorer les performances de Polyphemus pour le Liban, notamment en améliorant la représentation des conditions aux limites du modèle, évaluer le modèle pour l’année 2014 vis-à-vis des nouvelles observations du réseau national de la qualité de l’air, mesurer les facteurs d’émissions du transport routier dans un tunnel à Beyrouth et les comparer aux données des pays développés. Afin d’améliorer les performances du CTM pour le Liban, cette thèse compare les concentrations simulées avec deux inventaires d’émissions différents et avec différentes méthodes de calcul des conditions aux limites. Pour les émissions, deux inventaires sont comparés : un inventaire récemment mise en place pour le Liban et l’inventaire d’émission global EDGAR-HTAP, qui combine des émissions mesurées pour les pays développés et des émissions modélisées pour les autres pays. Bien que cet inventaire soit couramment utilisé dans les modèles globaux de qualité de l’air d’importantes différences d’estimation et de distribution spatiale sont identifiées par rapport à l’inventaire spécifique du Liban. Dans les simulations des études précédentes réalisées sur le Liban, les conditions aux limites étaient obtenues à partir de simulations globales avec le modèle MOZART-4. Un domaine régional sur le Moyen-Orient est introduit dans la chaine de modélisation afin d’amortir le changement de résolution entre les résultats le modèle global (≥ 1°) et le domaine du Liban (0.055°). Ce changement a permis d’améliorer considérablement les résultats de la modélisation des polluants au Liban, surtout pour l’ozone. Cette nouvelle configuration de modélisation (domaines emboités, Moyen Orient puis Liban) est ensuite employée pour la modélisation de l’année 2014 et évaluée vis-à-vis des observations faites par le réseau national de mesure de la qualité de l’air. Les performances du modèle pour la représentation des polluants de qualité de l’air sont satisfaisantes par rapport aux indicateurs disponibles dans la littérature. Cependant, la modélisation météorologique pourrait être améliorée, et il serait souhaitable de prendre en compte l’impact sur les émissions des changements démographiques entre l’année pour laquelle l’inventaire a été conçu (2011) et l’année modélisée (2014) en raison du déplacement de population suite à la guerre en Syrie.En ce qui concerne des facteurs d’émission (FE) du transport routier, nous avons effectué une campagne de mesure au tunnel Salim Slam à Beyrouth en 2014. Les facteurs d’émissions de différents polluants (CO, NOx, PM2.5, COV) ont été mesurés pour l’ensemble du trafic. En comparaison à la littérature, les FE locaux sont toujours supérieurs aux FE des pays développés même s’ils ont tendances à être réduits par rapport aux valeurs mesurés en 2000 suites aux changements du parc automobile et son évolution (10.70675/a671a315z83cfz4ab2z8b2cz55f6181d0250)
  DOI : 10.70675/a671a315z83cfz4ab2z8b2cz55f6181d0250
• Environmental quality at district scale: A transdisciplinary approach within the EUREQUA project
  
  • Gauvreau Benoit
  • Guillaume Gwenaël
  • Can Arnaud
  • Gaudio Noémie
  • Julien Le Bras
  • Lemonsu Aude
  • Masson Valéry
  • Carissimo Bertrand
  • Richard Isabelle
  • Haouès-Jouve Sinda
  , 2016, pp.13p. This paper presents a research project entitled EUREQUA (Multidisciplinary Assessment and Environmental Requalification of districts) that adopts an original methodological approach relying on a multidisciplinary team of researchers in physics, environmental, human and social sciences (geographers, sociologists, atmospheric physicists, acousticians, architects, etc.) in collaboration with officials of urban living. The EUREQUA project (2012-2017) implements a transdisciplinary approach because it focuses on 3 main observables (climate comfort, air quality and sound environment) and because it combines experimental, numerical and statistical methods. This paper focuses on one district particularly studied within the EUREQUA project, both experimentally and numerically. This paper also briefly expose the methodology and how qualitative and quantitative results are jointly processed and combined in order to make environmental criteria emerge in scenarii conception, through statistical data cross-analysis, feedback meetings with inhabitants and participative workshops
• Using the Wasserstein distance to compare fields of pollutants: application to the radionuclide atmospheric dispersion of the Fukushima-Daiichi accident
  
  • Farchi Alban
  • Bocquet Marc
  • Roustan Yelva
  • Mathieu Anne
  • Quérel Arnaud
  Tellus B - Chemical and Physical Meteorology, Taylor & Francis, 2016, 68 (1). The verification of simulations against data and the comparison of model simulation of pollutant fields rely on the critical choice of statistical indicators. Most of the scores are based on point-wise, that is, local, value comparison. Such indicators are impacted by the so-called double penalty effect. Typically, a misplaced blob of pollutants will doubly penalise such a score because it is predicted where it should not be and is not predicted where it should be. The effect is acute in plume simulations where the concentrations gradient can be sharp. A non-local metric that would match concentration fields by displacement would avoid such double penalty. Here, we experiment on such a metric known as the Wasserstein distance, which tells how penalising moving the pollutants is. We give a mathematical introduction to this distance and discuss how it should be adapted to handle fields of pollutants. We develop and optimise an open Python code to compute this distance. The metric is applied to the dispersion of cesium-137 of the Fukushima-Daiichi nuclear power plant accident. We discuss of its application in model-to-model comparison but also in the verification of model simulation against a map of observed deposited cesium-137 over Japan. As hoped for, the Wasserstein distance is less penalising, and yet retains some of the key discriminating properties of the root mean square error indicator. (10.3402/tellusb.v68.31682)
  DOI : 10.3402/tellusb.v68.31682
• Distribution, optical properties, and radiative effect of pollution aerosols in the western mediter- ranean basin from TRAQA and SAFMED airborne observations.
  
  • Di Biagio Claudia
  • Gaimoz Cécile
  • Grand Noël
  • Ancellet Gérard
  • Attié Jean-Luc
  • Beekmann Matthias
  • Borbon Agnès
  • Bucci Silvia
  • Doppler Lionel
  • Dubuisson Philippe
  • Fierli Federico
  • Mallet Marc
  • Raut Jean-Christophe
  • Ravetta François
  • Sartelet Karine
  • Formenti Paola
  , 2016, pp.p1-aas-aap-050. Pollution aerosols strongly influence the composition of the western Mediterranean basin, but at present little is known on their distribution, optical properties and radiative effects. We report in this study in situ observations of pollution aerosol plumes obtained over the sea in the western Mediterranean during the TRAQA (TRansport and Air QuAlity) and the SAFMED (Secondary Aerosol Formation in the MEDiterranean) airborne campaigns in summers 2012 and 2013 (Di Biagio et al, 2015). The TRAQA and SAFMED flights explored an extended region of the western Mediterranean between 40°-45°N latitude and 2°W-12°E longitude including the Gulf of Genoa, Southern France, the Gulf of Lion, and the Spanish coasts. Measurements were performed over the sea at various distances from the coastline and up to 5000 m altitude. TRAQA and SAFMED successfully measured a wide range of meteorological conditions which favoured the pollution export from different sources around the basin.
• Modeling of the atmospheric dispersion of heavy metals over Poland
  
  • Zysk Janusz
  , 2016. Modelling of atmospheric transport of heavy metals emitted from Polish power sectorMany studies have been conducted to investigate the atmospheric heavy metals contamination and its deposition to ecosystems. The increasing attention to mercury pollution has been mainly driven by the growing evidence of its negative impacts on wildlife, ecosystems and particularly human health. Lead and cadium are also toxics which are being emitted into the atmosphere by anthropogenic as well as natural sources. The harmful influence of these three heavy metals was underlined in the Aarhus Protocol on Heavy Metals of 1998. The Parties of this protocol (including Poland) are obligated to reduce emissions, observe the transport and the amounts of lead, mercury and cadmium in the environment.Poland is one of the biggest emitter of mercury, lead and cadmium in Europe mainly due to emission from coal combustion processes. Therefore in Poland, research efforts to study the heavy metals emission, atmospheric transport, concentration and deposition are extremely important. The objectives of this work were twofold:• The practical objective was to develop and run a model to represent the atmospheric dispersion of mercury and to implement it in the air quality modelling platform Polyphemus.• The scientific objective was to perform heavy metals dispersion studies over Europe and detailed studies of the impact of the polish power sector on the air quality regarding mercury, cadmium and lead.To meet the declared aim, a new mercury chemical model was implemented into the Polyphemus air quality system. The scientific literature was reviewed regarding mercury chemistry and mercury chemical models. It can be concluded that the chemistry of mercury is still not well known. The models also differ in the way of calculating the dry and wet deposition of mercury. The elemental gaseous mercury ambient concentrations are evenly distributed, on the contrary, high variations in the spatial gradients of reactive gaseous and particulate forms of mercury air concentrations and deposition fluxes were noted.This study shows that many components of the developed model have crucial impacts on the results. In the model of mercury chemistry, the most effective pathway in the gaseous phase are the oxidation of gaseous elemental mercury by hydroxyl radical, ozone and most of all bromine oxide radicals, while in the aqueous phase the reduction reactions of elemental mercury dominate. These reactions have a crucial influence on the mass balance of reactive mercury, but a rather low influence on gaseous elemental mercury (GEM). In this model, dry deposition of gaseous elemental mercury is the prevailing process for removing mercury from the atmosphere. Dry deposition of GEM over land is equally distributed, due to almost uniform ambient concentrations. The relatively high dry deposition flux of gaseous elemental mercury has a huge influence on the presented results and differs significantly from other models where the dry deposition of GEM is often not taken into account. It was also shown that a change in the calculation of the scavenging coefficients or representative raindrop diameter for in-cloud scavenging has a significant impact on the amount of wet deposited mercury.The detailed results show that the Polish power sector can be responsible for up to 80% of wet deposited mercury near large emission sources. The contribution from national sources over whole Poland reaches 21% during the winter heating season when large quantities of coal are burned in the domestic sector and additionally the power sector activity is at its highest. The impact of emissions of cadmium and lead from the power sector is lower compared to the obtained results for mercury. The modelling results showed maximal impacts of 30% and 10% for cadmium and lead near large power sector sources on the ambient concentrations and deposition. Wider measurements of heavy metals are very much needed (10.70675/83b5f8a5zf358z445fz81d7z9c54c0ffea46)
  DOI : 10.70675/83b5f8a5zf358z445fz81d7z9c54c0ffea46
• Impact of changing the wet deposition schemes in ldx on 137-cs atmosperic deposits after the fukushima accident
  
  • Quérel Arnaud
  • Quélo Denis
  • Roustan Yelva
  • Mathieu Anne
  • Kajino Mizuo
  • Sekiyama Thomas
  • Adachi Kouji
  • Didier Damien
  • Igarashi Yasuhito
  • Maki Takashi
  , 2018, 2016, pp.598-602. The Fukushima-Daiichi release of radioactivity is a relevant event to study the atmospheric dispersion modelling of radionuclides. Actually, the atmospheric deposition onto the ground may be studied through the map of measured Cs-137 established consecutively to the accident. The limits of detection were low enough to make the measurements possible as far as 250km from the nuclear power plant. This large scale deposition has been modelled with the Eulerian model ldX. However, several weeks of emissions in multiple weather conditions make it a real challenge. Besides, these measurements are accumulated deposition of Cs-137 over the whole period and do not inform of deposition mechanisms involved: in-cloud, below-cloud, dry deposition. In a previous study (Quérel et al., 2016), a comprehensive sensitivity analysis was performed in order to understand wet deposition mechanisms. It has been shown that the choice of the wet deposition scheme has a strong impact on assessment of deposition patterns. Nevertheless, a “best” scheme could not be highlighted as it depends on the selected criteria: the ranking differs according to the statistical indicators considered (correlation, figure of merit in space and factor 2). A possibility to explain the difficulty to discriminate between several schemes was the uncertainties in the modelling, resulting from the meteorological data for instance. Since the move of the plume is not properly modelled, the deposition processes are applied with an inaccurate activity concentration in the air. In the framework of the SAKURA project, an MRI-IRSN collaboration, new meteorological fields at higher resolution (Sekiyama et al., 2013) were provided and allow to reconsider the previous study. An update including these new meteorology data is presented. In addition, the focus is put on the deposition schemes commonly used in nuclear emergency context.
• Impact of a laser pulse on HfO2-based RRAM cells reliability and integrity
  
  • Krakovinsky A.
  • Bocquet M.
  • Wacquez R.
  • Coignus J.
  • Deleruyelle Damien
  • Djaou C.
  • Reimbold G.
  • Portal J-M.
  , 2016, pp.152-156. Several NVM technologies have emerged during the last 10 years. These technologies offer solutions for the replacement of the Flash technology, which is facing downsizing limits [1]. Moreover these solutions propose lower switching energy and faster operations compared to the state of the art for Flash, and thus, are seen as an opportunity for the rise of the IoT market. But one of the main concerns regarding IoT is the protection of the data. Contrary to Flash, security of the data in emerging NVM is yet to be evaluated. In order to verify capability of the technology in terms of data integrity, we propose to investigate reliability and integrity of HfO2-based Resistive RAM (OxRRAM). This paper details the experimental protocol defined for laser-based attacks, shows that a laser pulse can affect the information stored in a single OxRRAM bit. The occurring phenomenon is then explained by mean of thermal and electrical simulations. (10.1109/ICMTS.2016.7476196)
  DOI : 10.1109/ICMTS.2016.7476196
• Experimental and numerical study of atmospheric turbulence and dispersion in stable conditions and in near field at a complex site
  
  • Wei Xiao
  , 2016. An experimental program has been designed in order to study pollutants dispersion at a complex site with a focus on stable conditions, which are still challenging for numerical modelling. This experimental program is being conducted at the SIRTA site in a southern suburb of Paris and consists in measuring, in near field, the turbulence and the pollutants dispersion. The aim of this program is to characterize the fine structure of turbulence and associated dispersion through high temporal and spatial resolution measurements. Then, these measurements allow to validate and improve the performance of CFD simulation for turbulence and dispersion in a heterogeneous field. The instrumental set up includes 12 ultrasonic anemometers measuring continuously wind velocity and temperature at 10 Hz, and 6 photo-ionization detectors (PIDs) measuring gas concentration at 50 Hz during tracer tests. Intensive observations periods (IOPs) with gas releases have been performed since March 2012.First of all, a detailed study of flow on the site is made, because it must be characterised and properly simulated before attempting to simulate the pollutants dispersion. This study is based on two years of continuous measurements and on measurements performed during IOPs. Turbulence strong anisotropy in the surface layer is characterized by calculating variances, integral length scales and power spectra of the three wind velocity components. Propagation of turbulent structures between sensors has been characterized with velocity correlations. Energy spectra show several slopes in different frequency regions. Also, data analyses show impact of terrain heterogeneity on the measurements. The forest to the north of experimental field modifies wind velocity and direction for a large northerly sector. It induces a strong directional wind shear and a wind deceleration below the forest height. Numerical simulations are carried out using the CFD code Code_Saturne in RANS mode with a standard k-ε closure adapted for atmospheric flows and a canopy model for the forest. These simulations are shown to reproduce correctly the characteristics of the mean flow on the measurements site, especially the impact of the forest for different wind directions, in both neutral and stable stratification. Simulations results also show the directional wind shear and the turbulent kinetic energy increase induced by the forest. A sensitivity study has been made for various values of forest density and shows that the typical features of canopy flow become more pronounced as canopy density increases. Pollutants dispersion study are made for several IOPs. Concentration data analysis shows a consistency with previous measurements made in a near-source region where the plume scale is smaller than the large-scale turbulence eddies. Concentration fluctuations are characterized through concentration time series, histogram and statistical analysis. The internal subrange can be observed in the concentration spectra. Next, pollutants dispersion are modelled by transport equations for concentration and its variance. The mean concentrations show a good agreement with measurements in values for all the IOPs studied, except that the position of the concentration peak depends on the accuracy of simulated wind rotation below the forest height. The concentration fluctuations obtained from simulations seem to be affected significantly by the initial condition and the modelling of the dissipation term. A sensitivity study to the parameterisation is then presented (10.70675/56c85fd0z7a97z42a5zbe7fz62b6420b8cb0)
  DOI : 10.70675/56c85fd0z7a97z42a5zbe7fz62b6420b8cb0
• Localization and the iterative ensemble Kalman smoother
  
  • Bocquet Marc
  Quarterly Journal of the Royal Meteorological Society, Wiley, 2016, 142 (695), pp.1075 - 1089. The iterative ensemble Kalman smoother (IEnKS) is a data assimilation method meant for tracking the state of nonlinear geophysical models efficiently. It combines an ensemble of model states to estimate the errors similarly to the ensemble square-root Kalman filter, with a four-dimensional variational analysis performed within the ensemble space. As such, it belongs to the class of four-dimensional ensemble variational methods. It could require the use of localization of the analysis when the state-space dimension is high. However, its localization needs to be defined across time and to be as consistent as possible with the dynamical flow within the data assimilation window where the four-dimensional variational analysis is performed. We show that a Liouville equation governs the time evolution of the localization operator, which is linked to the evolution of the error correlations. It is argued that the time evolution of the localization operator depends strongly on the forecast dynamics. Using either covariance localization or domain localization, we propose and test several localization strategies meant to address the issue: (i) a static and uniform localization, (ii) propagation through the window of a restricted set of dominant modes of the error covariance matrix and (iii) the approximate propagation of the localization operator using covariant local domains that are moved in accordance with the dynamical flow. These schemes are illustrated with the one-dimensional Lorenz 40 variable model and with a two-dimensional barotropic vorticity model. In both cases, local analysis based on the covariant local domains leads to a systematic improvement of the data assimilation performance. (10.1002/qj.2711)
  DOI : 10.1002/qj.2711
• A low-order coupled chemistry meteorology model for testing online and offline data assimilation schemes: L95-GRS (v1.0)
  
  • Haussaire M.
  • Bocquet Marc
  Geoscientific Model Development Discussions, Copernicus Publ, 2016, 9 (1), pp.393 - 412. Bocquet and Sakov (2013) introduced a low-order model based on the coupling of the chaotic Lorenz-95 (L95) model, which simulates winds along a mid-latitude circle, with the transport of a tracer species advected by this zonal wind field. This model, named L95-T, can serve as a playground for testing data assimilation schemes with an online model. Here, the tracer part of the model is extended to a reduced photochemistry module. This coupled chemistry meteorology model (CCMM), the L95-GRS (generic reaction set) model, mimics continental and transcontinental transport and the photochemistry of ozone, volatile organic compounds and nitrogen oxides. Its numerical implementation is described. The model is shown to reproduce the major physical and chemical processes being considered. L95-T and L95-GRS are specifically designed and useful for testing advanced data assimilation schemes, such as the iterative ensemble Kalman smoother (IEnKS), which combines the best of ensemble and variational methods. These models provide useful insights prior to the implementation of data assimilation methods into larger models. We illustrate their use with data assimilation schemes on preliminary yet instructive numerical experiments. In particular, online and offline data assimilation strategies can be conveniently tested and discussed with this low-order CCMM. The impact of observed chemical species concentrations on the wind field estimate can be quantitatively assessed. The impacts of the wind chaotic dynamics and of the chemical species non-chaotic but highly nonlinear dynamics on the data assimilation strategies are illustrated. (10.5194/gmd-9-393-2016)
  DOI : 10.5194/gmd-9-393-2016
• Études fines des échanges énergétiques entre les bâtiments et l'atmosphère urbaine
  
  • Daviau Noëlie
  , 2016. Le travail réalisé dans le cadre de cette thèse porte sur l'effet que les bâtiments exercent sur l'atmosphère urbaine et notamment sur les échanges énergétiques qui s'opèrent entre les deux systèmes. Afin de modéliser plus finement les effets thermiques du bâtiment sur les écoulements atmosphériques lors de simulations réalisées par le logiciel de CFD Code_Saturne, nous procédons au couplage de cet outil avec le modèle de bâtiment BuildSysPro. Cette bibliothèque fonctionne sous Dymola et peut calculer des matrices descriptives du bâtiment utilisables ensuite en dehors du logiciel. Ce sont donc ces matrices qui sont utilisées pour le couplage par l'intermédiaire d'un code assurant l'échange de données entre les calculs de thermique du bâtiment et ceux de CFD. Après une revue des phénomènes physiques en lien avec l'atmosphère urbaine et des modèles existants, nous nous intéressons aux interactions entre l'atmosphère et le milieu urbain, notamment les bâtiments. Ceux-ci peuvent avoir un impact sur les écoulements aussi bien dynamique, en tant qu'obstacles, que thermique, via leurs températures de parois. Parallèlement à la mise en place du couplage entre les deux logiciels, nous étudions les données de la campagne de mesures EM2PAU que nous utilisons pour notre validation. EM2PAU, réalisée en 2011 à Nantes, représente une rue canyon idéalisée par deux rangées de conteneurs. La campagne a pour spécificité de prendre simultanément les mesures de températures d'air et de parois ainsi que les vitesses du vent de référence et des écoulements dans le canyon par un anémomètre sonique placé à 10 m d'altitude et six autres positionnés en six emplacements dans le canyon. Nous cherchons donc à mettre en évidence les effets dynamiques et thermiques des bâtiments sur les écoulements à partir des résultats de cette campagne, pour ensuite les simuler. Puis la modélisation numérique des écoulements sur le domaine de EM2PAU est réalisée. L'objectif de ce travail est de mettre en évidence l'influence des effets thermiques des parois sur les flux atmosphériques. Nous comparons des simulations avec différentes méthodes pour donner les valeurs des températures de surface des conteneurs. La première méthode consiste à imposer ces températures d'après les mesures ; ainsi la température de chaque paroi sera fixée à la température de surface mesurée lors de l'instrumentation de EM2PAU. Quant à la deuxième méthode, on impose la température de l'air extérieur mesurée à l'instant simulé à toutes les parois des conteneurs, afin de créer un cas où l'on n'observe que peu ou pas d'échanges de chaleur. Enfin la troisième méthode est la simulation couplée de Code_Saturne et BuildSysPro. Les résultats des différentes simulations sont alors comparés afin de distinguer les effets thermiques des parois des bâtiments sur les écoulements d'air. Nous observons que les effets dynamiques sont primordiaux et peuvent engendrer des vitesses verticales de l'écoulement dans le canyon de l'ordre plusieurs mètres par seconde, tandis que des écarts de températures de surface de l'ordre de 15°C peuvent modifier les vitesses verticales du vent de moins de 0, 5 mètres par seconde. Si ces effets thermiques sont difficiles à isoler sur des mesures en raison des autres phénomènes susceptibles d'influencer les écoulements atmosphériques, les études numériques peuvent toutefois mieux quantifier ces différences (10.70675/f3e4b071z6d4cz4613zbfd8zc0fb2df3ae89)
  DOI : 10.70675/f3e4b071z6d4cz4613zbfd8zc0fb2df3ae89
• Data assimilation: methods, algorithms, and applications
  
  • Asch Mark
  • Bocquet Marc
  • Nodet Maëlle
  , 2016, pp.xviii + 306. Data assimilation is an approach that combines observations and model output, with the objective of improving the latter. This book places data assimilation into the broader context of inverse problems and the theory, methods, and algorithms that are used for their solution. It provides a framework for, and insight into, the inverse problem nature of data assimilation, emphasizing “why” and not just “how.” Methods and diagnostics are emphasized, enabling readers to readily apply them to their own field of study. Readers will find <ul> <li>a comprehensive guide that is accessible to nonexperts; <li>numerous examples and diverse applications from a broad range of domains, including geophysics and geophysical flows, environmental acoustics, medical imaging, mechanical and biomedical engineering, economics and finance, and traffic control and urban planning; <li>and the latest methods for advanced data assimilation, combining variational and statistical approaches. </ul>
• Oligomer formation in the troposphere : from experimental knowledge to 3-D modeling
  
  • Lemaire Vincent
  • Coll Isabelle
  • Couvidat Florian
  • Mouchel-Vallon Camille
  • Seigneur Christian
  • Siour Guillaume
  Geoscientific Model Development, European Geosciences Union, 2016, 9, pp.1361-1382. The organic fraction of atmospheric aerosols has proven to be a critical element of air quality and climate issues. However, its composition and the aging processes it undergoes remain insufficiently understood. This work builds on laboratory knowledge to simulate the formation of oligomers from biogenic secondary organic aerosol (BSOA) in the troposphere at the continental scale. We compare the results of two different modeling approaches, a first-order kinetic process and a pH-dependent parameterization, both implemented in the CHIMERE air quality model (AQM) (www.lmd.polytechnique.fr/chimere), to simulate the spatial and temporal distribution of oligomerized secondary organic aerosol (SOA) over western Europe. We also included a comparison of organic carbon (OC) concentrations at two EMEP (European Monitoring and Evaluation Programme) stations. Our results show that there is a strong dependence of the results on the selected modeling approach: while the irreversible kinetic process leads to the oligomerization of about 50 % of the total BSOA mass, the pH-dependent approach shows a broader range of impacts, with a strong dependency on environmental parameters (pH and nature of aerosol) and the possibility for the process to be reversible. In parallel, we investigated the sensitivity of each modeling approach to the representation of SOA precursor solubility (Henry's law constant values). Finally, the pros and cons of each approach for the representation of SOA aging are discussed and recommendations are provided to improve current representations of oligomer formation in AQMs. (10.5194/gmd-9-1361-2016)
  DOI : 10.5194/gmd-9-1361-2016
• Organic aerosol molecular composition and gas–particle partitioning coefficients at a Mediterranean site (Corsica)
  
  • Rossignol Stéphanie
  • Couvidat Florian
  • Rio Caroline
  • Fable Sébastien
  • Grignion Guillaume
  • Savelli Jean-Luc
  • Pailly Olivier
  • Leoz-Garziandia Eva
  • Doussin Jean-François
  • Chiappini Laura
  Journal of Environmental Sciences, Elsevier, 2016, 40, pp.92-104. Molecular speciation of atmospheric organic matter was investigated during a short summer field campaign performed in a citrus fruit field in northern Corsica (June 2011). Aimedat assessing the performance on the field of newly developed analytical protocols, this work focuses on the molecular composition of both gas and particulate phases and provides an insight into partitioning behavior of the semi-volatile oxygenated fraction. Limonene ozonolysis tracers were specifically searched for, according to gas chromatography–mass spectrometry (GC–MS) data previously recorded for smog chamber experiments. A screening of other oxygenated species present in the field atmosphere was also performed. About sixty polar molecules were positively or tentatively identified in gas and/or particle phases. These molecules comprise a wide range of branched and linear, mono and di-carbonyls (C3–C7), mono and di-carboxylic acids (C3–C18), and compounds bearing up to three functionalities. Among these compounds, some can be specifically attributed to limonene oxidation and others can be related to α- or β-pinene oxidation. This provides an original snapshot of the organic matter composition at a Mediterranean site in summer. Furthermore, for compounds identified and quantified in both gaseous and particulate phases, an experimental gas/particle partitioning coefficient was determined. Several volatile products, which are not expected in the particulate phase assuming thermodynamic equilibrium, were nonetheless present in significant concentrations. Hypotheses are proposed to explain these observations, such as the possible aerosol viscosity that could hinder the theoretical equilibrium to be rapidly reached. (10.1016/j.jes.2015.11.017)
  DOI : 10.1016/j.jes.2015.11.017
• Evaluation of some SOA formation schemes for the oxidation of anthropogenic gases against experiments in two outdoor chambers
  
  • Vivanco Marta G.
  • Couvidat Florian
  • Seigneur Christian
  • Jang Myoseon
  • Santiago Manuel
  • Bessagnet Bertrand
  International Journal of Environment and Pollution, Inderscience, 2016, 59 (1), pp.43-55. Secondary organic aerosol (SOA) formation remains a challenge for the air quality modelling community. Gaps in the current knowledge of certain processes involved in SOA formation and evolution, as well as the large number of uncertainties in many parameters involved, affect the accuracy of the simulation of atmospheric SOA concentrations. We present here an evaluation of several published SOA schemes by simulating experiments conducted in two outdoor chambers, EUPHORE (Ceam, Valencia, Spain) and UF (University of Florida, Gainesville, USA). The experiments focused on the oxidation of selected anthropogenic volatile organic compounds. We compare model estimates for one-step, two-step and multi-step gas-phase oxidation schemes with SOA concentrations measured in the chambers. For all schemes, some modifications were needed to obtain a better agreement between model simulations and observations. (10.1504/IJEP.2016.078062)
  DOI : 10.1504/IJEP.2016.078062
• Three-dimensional modeling of the mixing state of particles over Greater Paris: 3-D MIXING STATE MODELING
  
  • Zhu Shupeng
  • Sartelet Karine
  • Zhang Yang
  • Nenes Athanasios
  Journal of Geophysical Research: Atmospheres, American Geophysical Union, 2016, 121 (10), pp.5930-5947. (10.1002/2015jd024241)
  DOI : 10.1002/2015jd024241
• Experimental and Numerical Study of Wind and Turbulence in a Near-Field Dispersion Campaign at an Inhomogeneous Site
  
  • Wei Xiao
  • Dupont Eric
  • Gilbert Eric
  • Musson-Genon Luc
  • Carissimo Bertrand
  Boundary-Layer Meteorology, Springer Verlag, 2016, 160 (3), pp.475-499. (10.1007/s10546-016-0148-7)
  DOI : 10.1007/s10546-016-0148-7
• A New Method for Fast Computation of Three-Dimensional Atmospheric Infrared Radiative Transfer in a Nonscattering Medium, with an Application to Dynamical Simulation of Radiation Fog in a Built Environment
  
  • Makké Laurent
  • Musson-Genon Luc
  • Carissimo Bertrand
  • Plion Pierre
  • Milliez Maya
  • Douce Alexandre
  Journal of the Atmospheric Sciences, American Meteorological Society, 2016, 73 (10), pp.4137-4149. (10.1175/jas-d-15-0012.1)
  DOI : 10.1175/jas-d-15-0012.1
• Effect of measurement protocol on organic aerosol measurements of exhaust emissions from gasoline and diesel vehicles
  
  • Kim Youngseob
  • Sartelet Karine
  • Seigneur Christian
  • Charron Aurélie
  • Besombes Jean-Luc
  • Jaffrezo Jean-Luc
  • Marchand Nicolas
  • Polo Lucie
  Atmospheric Environment, Elsevier, 2016, 140, pp.pp. 176-187. h i g h l i g h t s Differences in the measured concentrations of organic carbon (OC) are observed. The differences are mainly due to different times elapsed during sampling. Semi-volatile organic compounds (SVOC) are not at equilibrium for short elapsed times. Gas-phase fraction of emitted SVOC leads to an underestimation of emitted OC. Estimated gas-phase SVOC suggest an underestimation of gas þ particle SVOC by 60%. (10.1016/j.atmosenv.2016.05.045)
  DOI : 10.1016/j.atmosenv.2016.05.045
• L'expertise est-elle soluble dans la modélisation intégrée ?
  
  • Commenges Hadrien
  • Tomasoni L.
  • Seigneur Christian
  • Bonin Olivier
  • Leurent Fabien
  • Bonhomme Céline
  • Deroubaix José-Frédéric
  , 2016. La question des relations entre les dispositifs d'évaluation et l'élaboration de politiques publiques a été largement étudiée en sciences politiques et dans le domaine des STS (sciences-technologie-société). Cependant, peu d'études portent spécifiquement sur le rôle de la modélisation numérique. Certains auteurs ont affirmé le rôle de la modélisation comme pont entre connaissance et action mais cette affirmation reste souvent une profession de foi. D'un côté, les modélisateurs se concentrent principalement sur les aspects techniques de la modélisation et s'intéressent peu à son utilisation pour l'élaboration des politiques publiques. De leur côté, les politistes s'intéressent bien à l'utilisation des connaissances pour l'élaboration des politiques publiques, mais ils se focalisent rarement sur les techniques de modélisation comme mode de production spécifique de connaissances. Ce travail explore l'usage et l'utilité des modèles urbains pour la mise en place d'instruments d'action publique, en particulier dans le domaine de l'aménagement urbain.
• Simulation of particle diversity and mixing state over Greater Paris: a model–measurement inter-comparison
  
  • Zhu Shupeng
  • Sartelet Karine N.
  • Healy Robert M.
  • Wenger John C.
  Faraday Discussions, Royal Society of Chemistry, 2016, 189, pp.547-566. (10.1039/c5fd00175g)
  DOI : 10.1039/c5fd00175g