Top Stories at CEREA

• Friday 5 April, 2013 at 9:30 am: Karine Sartelet will defend her « habilitation à diriger des recherches » (HDR)

  Title:: Regional air quality modeling

  Location: 19, rue Alfred Nobel, FR-77420 Champs-sur-Marne, in Freyssinet amphitheater (Nobel buildings)

  Jury:

  • Pr Hiroshi Hayami, CRIEPI, Japan (reviewer)
  • Dr Céline Mari, Laboratoire d’aérologie, Toulouse (reviewer)
  • Pr Robert Rosset, Laboratoire d’aérologie, Université de Toulouse (reviewer)
  • Dr Matthias Beekmann, LISA, UPEC (examiner)
  • Dr Solène Turquety, LMD (examiner)
  • Pr Christian Seigneur, CEREA, Université Paris-Est (HDR director)

• On December 20th, 2012 at 14h00: Mohammad Reza Koohkan will defend his PhD thesis

  Title: Multiscale data assimilation approaches and error characterisation applied to the inverse modelling of atmospheric constituent emission fields.

  Location: 19, rue Alfred Nobel, FR-77420 Champs-sur-Marne, in Freyssinet amphitheater (Nobel buildings)

  Jury:

  • Dr. Olivier Talagrand, CNRS/LMD (president)
  • Dr. Frédéric Chevallier, CEA/LSCE (referee)
  • Dr. Slimane Bekki, CNRS/LATMOS (referee)
  • Dr. Gilles Forêt, UPEC/LISA (reviewer)
  • Dr. Sébastien Massart, ECMWF (reviewer)
  • Dr. Marc Bocquet, École des Ponts ParisTech/CEREA (thesis director)

  Summary: Data assimilation in geophysical sciences aims at optimally estimating the state of the system or some parameters of the system?s physical model. To do so, data assimilation needs three types of information : observations and background information, a physical/numerical model, and some statistical description that prescribes uncertainties to each componenent of the system. In my dissertation, new methodologies of data assimilation are used in atmospheric chemistry and physics : the joint use of a 4D-Var with a subgrid statistical model to consistently account for representativeness errors, accounting for multiple scale in the BLUE estimation principle, and a better estimation of prior errors using objective estimation of hyperparameters. These three approaches will be specifically applied to inverse modelling problems focussing on the emission fields of tracers or pollutants.

  First, in order to estimate the emission inventories of carbon monoxide over France, in-situ stations which are impacted by the representativeness errors are used. A subgrid model is introduced and coupled with a 4D-Var to reduce the representativeness error. Indeed, the results of inverse modelling showed that the 4D-Var routine was not fit to handle the representativeness issues. The coupled data assimilation system led to a much better representation of the CO concentration variability, with a significant improvement of statistical indicators, and more consistent estimation of the CO emission inventory.

  Second, the evaluation of the potential of the IMS (International Monitoring System) radionuclide network is performed for the inversion of an accidental source. In order to assess the performance of the global network, a multiscale adaptive grid is optimised using a criterion based on degrees of freedom for the signal (DFS). The results show that several specific regions remain poorly observed by the IMS network.

  Finally, the inversion of the surface fluxes of Volatile Organic Compounds (VOC) are carried out overWestern Europe using EMEP stations. The uncertainties of the background values of the emissions, as well as the covariance matrix of the observation errors, are estimated according to the maximum likelihood principle. The prior probability density function of the control parameters is chosen to be Gaussian or semi-normal distributed. Grid-size emission inventories are inverted under these two statistical assumptions. The two kinds of approaches are compared. With the Gaussian assumption, the departure between the posterior and the prior emission inventories is higher than when using the semi-normal assumption, but that method does not provide better scores than the semi-normal in a forecast experiment.

• On December 14th, 2012 at 14h00: Hilel Dergaoui will defend his PhD thesis

  Title: Coagulation d'une population d'aérosols en mélange externe: modélisation et expériences.

  Location: at ENSG school, 6-8 avenue Blaise Pascal, FR-77455 Champs-sur-Marne, in Picard amphitheater (access ENSG hallway)

  Jury:

  • Pr. Laurence LE COQ, École des Mines de Nantes (referee)
  • Dr. Laurent MENUT, Laboratoire de Météorologie Dynamique (referee)
  • Pr. Robert ROSSET, Laboratoire d'Aérologie, Université de Toulouse (reviewer)
  • Pr. Jean-François DOUSSIN, LISA, Université Paris-Est (reviewer)
  • Dr. Olivier LE BIHAN, INERIS (reviewer)
  • Dr. Édouard DEBRY, INERIS (thesis co-supervisor)
  • Dr. Karine SARTELET, École des Ponts ParisTech, CEREA (thesis co-supervisor)
  • Pr. Christian SEIGNEUR, École des Ponts ParisTech, CEREA (thesis director)

• On November 23th, 2012 at 14h00: Marion Devilliers will defend his PhD thesis

  Title: Modeling and numerical simulation of the dynamics of nanoparticles applied to free and confined atmospheres.

  Location: at ENSG school, 6-8 avenue Blaise Pascal, FR-77455 Champs-sur-Marne, in Picard amphitheater (access ENSG hallway)

  Jury:

  • Robert ROSSET, LA, Toulouse (president)
  • Virginie MARECAL, CNRM-GAME, Toulouse (referee)
  • Olivier SIMONIN, INPT/IMFT, Toulouse (referee)
  • Matthias BEEKMANN, LISA, Créteil (reviewer)
  • Didier HAUGLUSTAINE, LSCE/LIVE, Gif-sur-Yvette (reviewer)
  • Pr. Christian SEIGNEUR, École des Ponts ParisTech, CEREA, Marne-La-Vallée (thesis director)
  • Edouard DEBRY, INERIS, Verneuil-en-Halatte (thesis supervisor)

  Summary: Nanoparticle technology is undergoing constant development in the industry and air quality measurements reveal an increasing presence of nanoparticles in the ambient air. These particles, which have a characteristic dimension lower than 100 nm, are also called ultra fine particles (UFPs). Current scientific knowledge regarding nanoparticles is still incomplete, which raises new questions for human health and the environment.

  These particles constitute the lower part of the size distribution of atmospheric particles. They contribute little to the mass concentrations of PM_2.5 and PM₁₀ (atmospheric particles which aerodynamic diameter is lower than 2.5 or 10 microns, respectively), but they represent the quasi-totality of the number concentration.

  Several studies have identified various emission and formation sources of nanoparticles in indoor and outdoor air. Studies have also shown that, because of their small size, these particles can cross the physiological lung barrier and subsequently penetrate very deeply into the human body. Furthermore, by penetrating fungal, animal, plant or microbial bodies, nanoparticles may change via bioaccumulation the evolution of ecosystems. Effects on the properties of clouds have also been brought to light.

  Currently, most indicators and air quality models focus on the mass concentration. However, the forthcoming regulatory indicators with respect to nanoparticles are likely to consider the number concentration, their relevant quantity. Thus, it is necessary to adapt existing models in order to simulate the number concentration, and correctly account for nanoparticles, in both free and confined atmospheres.

  A model of particle dynamics capable of following accurately the number as well as the mass concentration of particles, with an optimal calculation time, has been developed.

  The dynamics of particles depends on various processes, the most important ones being condensation/evaporation, followed by nucleation, coagulation, and deposition phenomena. These processes are well-known for fine and coarse particles, but some additional phenomena must be taken into account when applied to nanoparticles, such as the Kelvin effect for condensation/evaporation and the van der Waals forces for coagulation.

  This work focused first on condensation/evaporation, which is the most numerically challenging process. Particles were assumed to be of spherical shape. The Kelvin effect has been taken into account as it becomes significant for particles with diameter below 50 nm. The numerical schemes are based on a sectional approach: the particle size range is discretized in sections characterized by a representative diameter. A redistribution algorithm is used, after condensation/evaporation occurred, in order to keep the representative diameter between the boundaries of the section. The redistribution can be conducted in terms of mass or number. The key point in such algorithms is to choose which quantity has to be redistributed over the fixed sections. We have developed a hybrid algorithm that redistributes the relevant quantity for each section. This new approach has been tested and shows significant improvements with respect to most existing models over a wide range of conditions.

  The process of coagulation for nanoparticles has also been solved with a sectional approach. Coagulation is monitored by the brownian motion of nanoparticles. This approach is shown to be more efficient if the coagulation rate is evaluated using the representative diameter of the section, rather than being integrated over the whole section. Simulations also reveal that the van der Waals interactions greatly enhance coagulation of nanoparticles.

  Nucleation has been incorporated into the newly developed model through a direct source of nanoparticles in the first size section, beginning at one nanometer. The formulation of this rate of nucleation corresponds to that of sulfuric acid but the treatment of the numerical interactions between nucleation, coagulation and condensation/evaporation is generic.

  Various strategies aiming to solve separately or jointly these three processes are discussed. In order to provide recommendations, several numerical splitting methods have been implemented and evaluated regarding their CPU times and their accuracy in terms of number and mass concentrations.

• On November 16th, 2012 at 9h30: Régis Briant will defend his PhD thesis

  Title: Multi-scale modeling of roadway traffic impact on air quality.

  Location: 19, rue Alfred Nobel, FR-77420 Champs-sur-Marne, in Freyssinet amphitheater (Nobel buildings)

  Jury:

  • Emeritus Pr. Robert Rosset, Laboratoire d'Aérologie OMP (referee and jury president)
  • Pr. Akula Venkatram, University of California Riverside (referee)
  • Dr. Lionel Soulhac, École Centrale de Lyon (reviewer)
  • Dr. Korsakissok, IRSN (reviewer)
  • Pr. Christian Seigneur, École des Ponts ParisTech, CEREA (thesis director)

  Summary: Roadway traffic contributes to atmospheric pollution near roads, with pollutants such as nitrogen dioxide (NO₂), particles (PM) along with some volatile organic compounds (VOC), as well as at larger spatial scales (urban and regional background pollution) with pollutants formed in the atmosphere such as ozone (O₃) and the secondary fraction of PM. Because of interactions between local and background pollutants, it is desirable to combine into a single computational tool, regional and local scale models. This multi-scale modeling method has been widely used to simulate the impact of chimney emissions (point sources) with a sub-grid treatment of plume or puff models instead within a 3-dimensional Eulerian model. However, such a method is not applicable to a road network because of the prohibitive computations associated with the line source discretization into a set of point sources. Thus, a new multi-scale modeling method was developed, which treats the plumes emitted from line sources as sub-grid components of an Eulerian model. First, an improved formulation of a Gaussian plume model for line sources was developed. This new model was then subject to a detailed evaluation with near roadway measurements along with other Gaussian models. The incorporation of the Gaussian plume model into an Eulerian model (Polair3D) was implemented as part of the modeling platform Polyphemus. The performance (computational effectiveness and precision) of the new multi-scale model (Plume-in-Grid) was evaluated and compared to those of a stand-alone Gaussian and Eulerian models. The multi-scale model treats nitrogen oxide (NO_x) chemistry along with major VOC. The multi-scale treatment has an important effect on the concentration of some pollutants in terms of local and urban background pollution.

• On November 15th, 2012 at 9h30: Florian Couvidat will defend his PhD thesis

  Title: Organic aerosols modelization in atmosphere.

  Location: 5, boulevard Descartes, FR-77420 Champs-sur-Marne, in François Rablais building, A3 amphitheater

  Jury:

  • Dr. Céline MARI, Université de Toulouse (president)
  • Pr. Spyros PANDIS, Patras University, Greece and Carnegie-Mellon University, USA (referee, absent)
  • Pr. Anne MONOD, Université de Aix-Marseille (referee)
  • Dr. Isabelle COLL, LISA, UPEC (reviewer)
  • Dr. Nathalie POISSON, ADEME (reviewer)
  • Pr. Christian SEIGNEUR, CEREA (thesis supervisor)

  Summary: Organic aerosol formation in the atmosphere is investigated via the development of a new model named H²O (Hydrohilic/Hydrophobic Organics). First, a parametrization is developed to take into account secondary organic aerosol formation from isoprene oxidation. It takes into account the effect of nitrogen oxides on organic aerosol formation and the hydrophilic properties of the aerosols. This parametrization is then implemented in H²O along with some other developments and the results of the model are compared to organic carbon measurements over Europe. Model performance is greatly improved by taking into account emissions of primary semi-volatile compounds, which can form secondary organic aerosols after oxidation or can condense when temperature decreases. If those emissions are not taken into account, a significant underestimation of organic aerosol concentrations occurs in winter. The formation of organic aerosols over an urban area was also studied by simulating organic aerosols concentration over the Paris area during the summer campaign of Megapoli (July 2009). H²O gives satisfactory results over the Paris area, although a peak of organic aerosol concentrations from traffic, which does not appear in the measurements, appears in the model simulation during rush hours. It could be due to an underestimation of the volatility of organic aerosols. It is also possible that primary and secondary organic compounds do not mix well together and that primary semi volatile compounds do not condense on an organic aerosol that is mostly secondary and highly oxidized. Finally, the impact of aqueous-phase chemistry was studied. The mechanism for the formation of secondary organic aerosol includes in-cloud oxydation of glyoxal, methylglyoxal, methacrolein and methylvinylketone, formation of methyltetrols in the aqueous phase of particles and cloud droplets, and the in-cloud aging of organic aerosols. The impact of wet deposition is also studied to better estimate the impact of clouds on organic aerosol concentrations.

• On September 28th, 2012: Antoine Waked has successfully defended his PhD thesis, a pioneering work on air quality at Beirut, Lebanon capital:

  Thesis Title: Organic aerosol characterization at Beirut, Lebanon (In french: Caractérisation des aérosols organiques à Beyrouth, Liban)

  Location: 19, rue Alfred Nobel, FR-77420 Champs-sur-Marne, Freyssinet amphitheater (Nobel buildings)

  Jury:

  • Pr. José Maria Baldasano, Barcelona Supercomputing Centre, Barcelona, Spain (president)
  • Dr. Jean-Luc Jaffrezo, research director at LGGE, Université Joseph Fourrier (referee)
  • Pr. Catherine Liousse, Laboratoire d'Aérologie, Université Paul Sabatier (reviewer)
  • Dr. Jean-Luc Ponche, LMSPC, Université de Strasbourg (reviewer)
  • Pr. Christian Seigneur, CEREA, École des ponts ParisTech (thesis co-director)
  • Dr. Charbel Afif, Centres d'analyses et de recherche, Faculté des Sciences, Université Saint Joseph, Beirut, Lebanon (thesis co-director)

  Summary: Study of air quality in Beirut (the capital city of Lebanon) with a focus on organic aerosols:

  • Development of an air pollutant emission inventory for Lebanon with a spatial resolution of 5 km x 5 km and for Beirut with a spatial resolution of 1 km x 1 km.
  • Characterization of air pollutant concentrations thanks to two intensive 15-day measurement campaigns conducted at a semi-urban site located in a Beirut suburb.
  • Air pollutant concentrations simulation in Beirut for July 2011 with Polyphemus/Polair3D chemical-transport model (CTM). The emission inventory mentioned above was used as input to the model.

• Marie Dumont, registered at Cerea for her Ph.D., has been awarded one of the "Prix solennels de Chancellerie" given by the Chancelor Office of the Universities of Paris : the Science Prize - Aguirre-Basualdo Prize, for her thesis titled "Determination by remote sensing of the albedo of snow surfaces - Application to the reconstruction of the mass budget of the Saint Sorlin glacier", performed at the Laboratoire de Glaciologie et Géophysique de l'Environnement in Grenoble.

• On December 15th, 2011: Youngseob KIM has successfully defended his PhD thesis.

  Title: Evaluation of chemical and meteorological parameterizations

  Location: 19, rue Alfred Nobel, FR-77420 Champs-sur-Marne, in Freyssinet amphitheater (Nobel buildings)

  Jury:

  • Pr. Bernard Aumont, Université Paris-Est (president)
  • Dr. Olivier Boucher, CNRS, Université Pierre et Marie Curie (reviewer)
  • Emeritus Pr. Robert, Rosset Université Paul Sabatier (reviewer)
  • Dr. Yves Balkanski, IPSL/LSCE (referee)
  • Dr. Sylvain Dupont, INRA (referee)
  • Mme Deborah Luecken US EPA (reviewer)
  • Dr. Karine Sartelet, CEREA (thesis co-supervisor)
  • Pr. Christian Seigneur École des Ponts ParisTech, CEREA (thesis supervisor)

  Summary: The influence of chemical mechanisms and meteorological parameterizations on pollutant concentrations calculated with an air quality model is studied. The influence of the differences between two gas-phase chemical mechanisms on the formation of ozone and aerosols in Europe is low on average. For ozone, the large local differences are mainly due to the uncertainty associated with the kinetics of nitrogen monoxide (NO) oxidation reactions on the one hand and the representation of different pathways for the oxidation of aromatic compounds on the other hand. The aerosol concentrations are mainly influenced by the selection of all major precursors of secondary aerosols and the explicit treatment of chemical regimes corresponding to the nitrogen oxides (NOx) levels. The influence of the meteorological parameterizations on the concentrations of aerosols and their vertical distribution is evaluated over the Paris region in France by comparisons to lidar data. The influence of the parameterization of the dynamics in the atmospheric boundary layer is important; however, it is the use of an urban canopy model that improves significantly the modeling of the pollutant vertical distribution.

• On December 14th, 2011: Damien Garaud has successfully defended his PhD thesis.

  Thesis Title: Uncertainty estimation and risk prediction in air quality

  Location: 19, rue Alfred Nobel, FR-77420 Champs-sur-Marne, Freyssinet amphitheater (Nobel buildings)

  Jury:

  • Pr. Matthias Beekmann, CNRS (president)
  • Pr. Serge Guillas, University College London (referee)
  • Dr. Jean-Luc Ponche, Université de Strasbourg (referee)
  • Dr.Frédérik Meleux, INERIS (reviewer)
  • Dr. Isabelle Herlin, INRIA (thesis supervisor)
  • Dr. Vivien Mallet, INRIA (thesis co-supervisor)

  Summary: This work is about uncertainty estimation and risk prediction in air quality. Firstly, we need to build an ensemble of air quality simulations which can take into account all uncertainty sources related to air quality modeling. Ensembles of photochemical simulations at continental and regional scales are automatically built. Then, these generated ensemble are calibrated with a combinatorial optimization method. It selects a sub-ensemble which is representative of uncertainty or has good resolution and reliability of probabilistic forecasts. Thus, this work show that it is possible to estimate and forecast uncertainty fields related to ozone and nitrogen dioxide concentrations or to improve reliability related to the threshold exceedance prediction. This approach is compared with Monte Carlo ensemble calibration. This ensemble is less representative of uncertainty. Finally, we can estimate the part of the measure error, representativity error and modeling error in air quality.

• On November 18th, 2011: Yongfeng Qu defended his Ph.D. thesis successfully!

• On November 18th, 2011 at 2:00pm: Yongfeng Qu will defend his PhD thesis

  Title: Three-dimensional modeling of radiative and convective exchanges in the urban atmosphere

  Location : 19, rue Alfred Nobel, FR-77420 Champs-sur-Marne, dans l'amphithéatre Freyssinet (bâtiments Nobel)

  Defense comittee:

  • Dr. Majorie MUSY, CERMA (reviewer)
  • Dr. Valéry MASSON, Météo-France (reviewer)
  • Pr. Jean François SINI - École Centrale de Nantes (examinator)
  • Pr. Jean Philippe GASTELLU-ETCHEGORRY, CESBIO (examinator)
  • Pr. Marina K.A. NEOPHYTOU, University of Cyprus (examinator)
  • Dr. Patrice G. MESTAYER, IRSTV (examinator)
  • Dr. Bertrand CARISSIMO, CEREA (advisor)
  • Dr. Maya MILLIEZ, CEREA (co-advisor)
  • Dr. Luc MUSSON-GENON, CEREA (co-advisor)

  Abstract : In many micrometeorological studies, building resolving models usually assume a neutral atmosphere. Nevertheless, urban radiative transfers play an important role because of their influence on the energy budget. In order to take into account atmospheric radiation and the thermal effects of the buildings in simulations of atmospheric flow and pollutant dispersion in urban areas, we have developed a three-dimensional (3D) atmospheric radiative scheme, in the atmospheric module of the Computational Fluid Dynamics model Code_Saturne. The radiative scheme was previously validated with idealized cases, using as a first step, a constant 3D wind field. In this work, the full coupling of the radiative and thermal schemes with the dynamical model is evaluated. The aim of the first part is to validate the full coupling with the measurements of the simple geometry from the Mock Urban Setting Test (MUST) experiment. The second part discusses two different approaches to model the radiative exchanges in urban area with a comparison between Code_Saturne and SOLENE. The third part applies the full coupling scheme to show the contribution of the radiative transfer model on the airflow pattern in low wind speed conditions in a 3D urban canopy. In the last part we use the radiative-dynamics coupling to simulate a real urban environment and validate the modeling approach with field measurements from the Canopy and Aerosol Particle Interactions in TOulouse Urban Layer (CAPITOUL).

• October 2011: Florian Couvidat, Ph.D. student at Cerea, received the Jean Bricart Award from the French Association for Aerosol Research (ASFERA) for his work on atmospheric organic aerosols.

• May 2010: Summary of the China's Cerea's tour (download here - in french)

• 29th March 2010: Publication of the final version of the AERES report comittee (in french)

• On February 19, 2010: Rachid Abida defended his Ph.D. thesis successfully!

• On February 19, 2010 at 2:00pm: Rachid Abida will defend his PhD thesis

  Title (in french): Construction optimale de réseaux fixes et mobiles pour la surveillance opérationnelle des rejets atmosphériques accidentels

  Location : 19, rue Alfred Nobel, FR-77420 Champs-sur-Marne, dans l'amphithéatre Freyssinet (bâtiments Nobel)

  Defense comittee:

  • M. Philippe Naveau (reviewer)
  • M. Hans Wackernagel (reviewer)
  • M. Olivier Isnard (referee)
  • M. Anda Ionescu (referee)
  • M. Werner G. Müller (Thesis supervisor)
  • M. Marc Bocquet (Thesis supervisor)

  Summary (in french) :

• On January 21, 2010: Hossein Malakooti defended his Ph.D. thesis successfully!

• On January 21, 2010 at 2:00pm: Hossein Malakooti will defend his PhD thesis

  Title: Meteorology and air-quality in a mega-city: application to Tehran, Iran

  Location : 19, rue Alfred Nobel, FR-77420 Champs-sur-Marne, dans l'amphithéatre Freyssinet (bâtiments Nobel)

  Defense comittee:

  • M. Alain Clappier (reviewer)
  • M. Abbas-Ali Ali-Akbari Bidokhti (reviewer)
  • M. Matthias Beekmann (referee)
  • M. Sylvain Dupont (referee)
  • M. Maya Milliez (referee)
  • M. Bruno Sportisse (Thesis supervisor)

  Summary : Tehran, capital of Iran, is located over a complex terrain with moderate to dry climate. The environmental problem that affects people more than any other in Tehran mega-city is air pollution. Sources of error in chemical-transport modeling processes may be grouped in three main categories, (I) emissions, (II) transport (including deposition) and (III) chemistry (including phase change). In this work, we tried to improve the quality of emission databases (part 1) and also meteorological simulations (part 2) in order to improvements of Tehran air quality calculations.

  1) Development and Evaluation of high resolution Emission Inventory An emission inventory of air pollutants and an inventory of heat generation were developed and updated for 2005 in this work. Emissions from on-road motor vehicles constitute a major portion of the emission inventory and play the most important role in terms of contributions of air pollutants to the atmosphere in Tehran. By using a detailed methodology, we calculated spatial and temporal distributions of the anthropogenic heat flux (Qf) for Tehran during 2005. Wintertime Qf is larger than summertime Qf, which reflects the importance of heating emissions from buildings and traffic during cold and warm period respectively.

  2) Local Meteorology and Urbanization Effects The influence of a mega-city on the atmospheric boundary layer and surface conditions was examined in Tehran region using the Pennsylvania State University/National Center for Atmospheric Research fifth-generation Mesoscale Model (MM5) during a high pollution period. In addition, model sensitivity studies were conducted to evaluate the performance of the urban canopy and urban soil model "SM2-U (3D)" parameterization on the meteorological fields. The topographic flows and urban effects were found to play important roles in modulating the wind and temperature fields, and the urbanized areas exerted important local effects on the boundary layer meteorology. Different urban parameterizations were used as a tool to investigate the modifications induced by the presence of an urban area in the area of interest. It was found that, for local meteorological simulations, the drag-force approach coupled with an urban soil model (DA-SM2-U) is preferable to the roughness approach (RA-SLAB). The comparisons indicated that the most important features of the wind, temperature and turbulent fields in urban areas are well reproduced by the DA-SM2-U configuration with the anthropogenic heat flux being taken into account (i.e., "DA-SM2-U Qf: On" option). This modeling option showed that the suburban part of the city is dominated by topographic flows whereas the center and south of Tehran are more affected by urban heat island (UHI) forcing especially during the night.

  3) Sensitivity and improvements of Tehran air quality calculations using different meteorological urban parameterization * The chemical transport modeling, including a model sensitivity study, was used to investigate the impact of the different urban parameterization on the dispersion and formation of pollutants over the Tehran region. Results show that applying DA approaches leads to significant improvements in the simulated spatial and temporal distribution of air pollutant concentrations in the city area and affects significantly the size of the urban plumes.

• On January 12, 2010: Xiaojing Zhang defended his Ph.D. thesis successfully!

• On January 12, 2010 at 2:00pm: Xiaojing Zhang will defend his Ph.D. thesis.

  Thesis title (in french): Modélisation du brouillard durant la campagne ParisFog : approche prédictive et étude de l'effet des hétérogénéités spatiales

  Location : 19, rue Alfred Nobel, FR-77420 Champs-sur-Marne, amphithéatre Freyssinet (bâtiments Nobel )

  Jury:

  • M. Jean-Pierre Chollet, Université Joseph Fourier (rapporteur)
  • M. Yves Brunet, INRA Bordeaux (rapporteur)
  • Mme. Andréa Flossmann, Université Blaise Pascal (examinatrice)
  • M. Patrick J. Mascart, Université Paul Sabatier (examinateur)
  • M. Martial Haeelin, IPSL (examinateur)
  • M. Thierry Bergot, Météo-France (directeur de thèse)
  • M. Luc Musson-Genon, EDF R&D (co-directeur de thèse)

• On December 15, 2009: Irène Bourdin-Korsakissok defended his Ph.D. thesis successfully!

• On December 15, 2009 at 2:30pm: Irène Bourdin-Korsakissok will defend her Ph.D. thesis.

  Thesis title: Multi-scale methods in air quality modeling, and estimation of the related uncertainties.

  Location : 19, rue Alfred Nobel, FR-77420 Champs-sur-Marne, amphithéatre Freyssinet (bâtiments Nobel )

  Jury:

  • M. Richard Perkins (rapporteur)
  • M. Robert Rosset (rapporteur)
  • M. Serge Guillas (examinateur)
  • M. Olivier Isnard (examinateur)
  • M. Vivien Mallet (co-directeur de thèse)
  • M. Bruno Sportisse (directeur de thèse)
  • M. Philippe Lameloise (invité)
  • Mme Laurence Rouïl (invitée)

• 13th August 2009: Publication of the report of activities for 2008

• On February 17, 2009: Christian Seigneur defended his HDR (Habilitation à Diriger des Recherches) successfully!

• On February 17, 2009 at 14:00: Christian Seigneur will defend his HDR (Habilitation à Diriger des Recherches).

  HDR's title: Modelling of atmospheric mercury

  Location : at 19, rue Alfred Nobel, FR-77420 Champs-sur-Marne, in the lecture hall Freyssinet (Nobel buildings)

  Jury:

  • Professor Lyatt Jaeglé, Université de Washington
  • Dr. Laurier Poissant, Environnement Canada
  • Professor Christophe Ferrari, Université de Grenoble
  • Professor Robert Rosset, Université de Toulouse
  • Professor Bernard Aumont, Université Paris 12 / Paris-Est

• February 2009: Publication of the dossier related to the assessment of the CEREA by the AERES (february 2009)

  • Presentation of the CEREA's summary report and scientific project (in french) .
  • CEREA's summary report for 2004-2008 period (in french/english) .
  • CEREA's scientific project for the 2010-2013 period (in french/english) .

• On December 12, 2008: Laurent Laporte defended his Ph.D. thesis successfully!

• April 2008: Publication in french of the CEREA's research dossier of the Ecole des Ponts (april 2008)

  Download it here .

• On March 28, 2008: Solen Queguiner defended her Ph.D. thesis successfully!

• On March 28, 2008 at 14:00: Solen Queguiner will defend her Ph.D. thesis.

  Thesis title: Coupled modelling of atmosphere-soil-vegetation in order to assess the effects of atmospheric emissions of heavy metals and persistent organic pollutants

  Location : au 19, rue Alfred Nobel, FR-77420 Champs-sur-Marne, dans l'amphithéatre Freyssinet (bâtiments Nobel )

  Jury:

  • M. Pierre Cellier (rapporteur)
  • M. Dimosthenis Sarigiannis (rapporteur)
  • Mme. Evelyne Gehin (examinatrice)
  • Mme. Laurence Rouil (examinatrice)
  • M. Philippe Ciffroy (examinateur)
  • M. Jean-Marie Mouchel (directeur de thèse)
  • M. Luc Musson-Genon (examinateur invité)

• On December 18, 2007: Marc Bocquet defended his HDR (Habilitation à Diriger des Recherches) successfully!

• On December 18, 2007 at 14:00: Marc Bocquet will defend his HDR (Habilitation à Diriger des Recherches).

  HDR's title: Modélisation inverse et assimilation de données non-gaussiennes pour les traceurs atmosphériques. Application à ETEX, Algésiras et Tchernobyl

  Location : au 19, rue Alfred Nobel, FR-77420 Champs-sur-Marne, dans l'amphithéatre Freyssinet (bâtiments Nobel )

  Jury:

  • M. Philippe Ciais (examinateur)
  • M. Hendrik Elbern (examinateur)
  • M. Nicolas Florsch (examinateur)
  • M. François-Xavier Le Dimet (rapporteur)
  • M. Bruno Sportisse (invité)
  • M. Olivier Talagrand (rapporteur)
  • M. Albert Tarantola (rapporteur)

• On November 30, 2007: Emmanuel Demaël defended his PhD successfully!

• On November 30, 2007 at 14h: Emmanuel Demaël will defend his PhD thesis.

  Thesis title: Modelling of atmospheric dispersion in complex areas and linked uncertainties

  Location : au 19, rue Alfred Nobel, FR-77420 Champs-sur-Marne, dans l'amphithéatre Freyssinet (bâtiments Nobel )

  Jury:

  • M. Jean-Pierre Chollet (rapporteur)
  • M. Jean-François Sini (rapporteur)
  • M. Richard Perkins (examinateur)
  • M. Olivier Isnard (examinateur)
  • M. Pierre Roubin (examinateur)
  • M. Bertrand Carissimo (directeur de thèse)

  Abstract: Nowadays, risk assessment studies of atmospheric industrial releases require the use of numerical tools. At local scale, Gaussian models are extensively used by operational units, because of their low computational coast. However, they may be partially or totally unsuitable in such cases where both buildings and complex terrain are involved. Atmospheric CFD (Computational Fluid Dynamics) models, among them RANS models, propose an interesting alternative but increase the computational coast. The purpose of this PhD work is to discuss the advantages given by CFD models with RANS approach for modelling near-field dispersion in complex areas. In a first step, these different approaches are compared on the Prairie Grass dispersion field experiment which consists in near-ground releases over a flat terrain. Here, Briggs (1973) and Doury (1976) Gaussian parameterisations are compared to Mercure_Saturne CFD model. In a second step, Mercure_Saturne is compared to ADMS (Atmospheric Dispersion Modelling System) for the modelling of dispersion on the Bugey nuclear power plant area wherebuildings have a great influence on dispersion processes due to their orientation relative to the main wind directions. This study is based on a wind-tunnel experiment conducted by the Fluid Mechanics and Acoustic Laboratory (LMFA, Ecole Centrale de Lyon). In a last step, the comparison is extended to the modelling of dispersion around the Flamanville nuclear power plant area which is in direct proximity of a stiff cliff. Finally, a last expectation concerns the evaluation of the predicted results variability due to input uncertainties. For this purpose, two approaches are proposed and applied to the modelling of the dispersion on the Bugey nuclear power plan area with Mercure_Saturne. The first one is the well-known Monte-Carlo method which may quantify in the same time the overall uncertainty on ground level concentrations and the influence of each input factor. The second one, the Morris' method, aims to rank these input factors in term of importance by a qualitative approach.

• On November 16, 2007: Marilyne Tombette defended her PhD thesis successfully.

• On November 16, 2007 at 14:00: Marilyne Tombette will defend her PhD thesis.

  Thesis title: Modélisation des aérosols et de leurs propriétés optiques sur l'Europe et l'Ile de France: validation, sensibilité et assimilation de données

  Location : au 19, rue Alfred Nobel, FR-77420 Champs-sur-Marne, dans l'amphithéatre Freyssinet (bâtiments Nobel )

  Jury:

  • M. Matthias Beekmann (rapporteur)
  • M. Robert Rosset (rapporteur)
  • M. Kees Cuvelier (examinateur)
  • M. Olivier Boucher (examinateur)
  • M. Patrick Chazette (directeur de thèse)
  • M. Bruno Sportisse (co-directeur de thèse)

  Abstract : Aerosols are a key component for studying the atmospheric composition. Actually, they have harmful sanitary consequences, modify the visibility and impact the radiative balance with a direct effect (absorption/scattering of light), a semi-direct effect (change of the temperature vertical profile) and a indirect effect (acting as cloud condensation nuclei). Aerosol modeling is a challenging issue, both at the physical and numerical levels. The objective of the PhD work is to evaluate the performances and the limitations of aerosol modeling systems at regional and continental scales. What is the robustness of the models and the comparisons with measured data? What could be the contribution of data assimilation methods? In a first part, a size-resolved aerosol model embedded in the Polyphemus platform is evaluated though a few regional cases (Europe and Ile-de-France) and for a few databases. The indicators are the PM10 (particles with a diameter lower than 10 micrometers), chemical composition and granulometry. The model outputs have also been extended in order to enable comparisons with optical data (optical thickness, extinction coefficient) measured by photometers or lidars. A second part investigates the sensitivity of the aerosol model with respect to physical parametrizations and numerical methods. This sensitivity analysis is the preliminary step before the use of ensemble method for aerosol forecasts, which appears to be a promising approach. A last part deals with the possible improvement induced by with a data assimilation system. The optimal interpolation method has then been implemented to assimilate PM10 data at ground level. The impact of data assimilation for forecast is also evaluated.

  
  
  

• 15th June 2007: Scientific Committee Meeting

  The Scientific Committee of CEREA aims at assessing the scientific quality of research projects carried out at CEREA. The meeting is the final evaluation meeting of CEREA for 2003-2007. Available reports: Prospective report 2008-2011 and Summary report 2003-2007 .

• June 2007: Publication of the Report of activities for year 2006

• november 2006-april 2007: PARISFOG

  The instrumental team of CEREA is involved in the equipment of the ground-based atmospheric observatory SIRTA and the measurement campaign PARISFOG.

• 15th September 2006: Scientific Committee meeting. "Planning".

  This meeting is the first step towards CEREA evaluation, which will take place next year. Each CEREA researcher made a short presentation to the scientific committee of his main results and actions during past year as well as his future works. Some of them are currently available on the meeting page .