Atmospheric composition forecasting in Europe

The atmospheric composition is a societal issue and, following new European directives, its forecast is now recommended to quantify the air quality. It concerns both gaseous and particles species, identified as potential problems for health. In Europe, numerical systems providing daily air quality forecasts are numerous and, mostly, operated by universities. Following recent European research projects (GEMS, PROMOTE), an organization of the air quality forecast is currently under development. But for the moment, many platforms exist, each of them with strengths and weaknesses. This overview paper presents all existing systems in Europe and try to identify the main remaining gaps in the air quality forecast knowledge. As modeling systems are now able to reasonably forecast gaseous species, and in a lesser extent aerosols, the future directions would concern the use of these systems with ensemble approaches and satellite data assimilation. If numerous improvements were recently done on emissions and chemistry knowledge, improvements are still needed especially concerning meteorology, which remains a weak point of forecast systems. Future directions will also concern the use of these forecast tools to better understand and quantify the air pollution impact on health

Presentation of the EURODELTA III intercomparison exercise – evaluation of the chemistry transport models' performance on criteria pollutants and joint analysis with meteorology

Abstract. The EURODELTA III exercise has facilitated a comprehensive intercomparison and evaluation of chemistry transport model performances. Participating models performed calculations for four 1-month periods in different seasons in the years 2006 to 2009, allowing the influence of different meteorological conditions on model performances to be evaluated. The exercise was performed with strict requirements for the input data, with few exceptions. As a consequence, most of differences in the outputs will be attributed to the differences in model formulations of chemical and physical processes. The models were evaluated mainly for background rural stations in Europe. The performance was assessed in terms of bias, root mean square error and correlation with respect to the concentrations of air pollutants (NO2, O3, SO2, PM10 and PM2.5), as well as key meteorological variables. Though most of meteorological parameters were prescribed, some variables like the planetary boundary layer (PBL) height and the vertical diffusion coefficient were derived in the model preprocessors and can partly explain the spread in model results. In general, the daytime PBL height is underestimated by all models. The largest variability of predicted PBL is observed over the ocean and seas. For ozone, this study shows the importance of proper boundary conditions for accurate model calculations and then on the regime of the gas and particle chemistry. The models show similar and quite good performance for nitrogen dioxide, whereas they struggle to accurately reproduce measured sulfur dioxide concentrations (for which the agreement with observations is the poorest). In general, the models provide a close-to-observations map of particulate matter (PM2.5 and PM10) concentrations over Europe rather with correlations in the range 0.4–0.7 and a systematic underestimation reaching −10 µg m−3 for PM10. The highest concentrations are much more underestimated, particularly in wintertime. Further evaluation of the mean diurnal cycles of PM reveals a general model tendency to overestimate the effect of the PBL height rise on PM levels in the morning, while the intensity of afternoon chemistry leads formation of secondary species to be underestimated. This results in larger modelled PM diurnal variations than the observations for all seasons. The models tend to be too sensitive to the daily variation of the PBL. All in all, in most cases model performances are more influenced by the model setup than the season. The good representation of temporal evolution of wind speed is the most responsible for models' skillfulness in reproducing the daily variability of pollutant concentrations (e.g. the development of peak episodes), while the reconstruction of the PBL diurnal cycle seems to play a larger role in driving the corresponding pollutant diurnal cycle and hence determines the presence of systematic positive and negative biases detectable on daily basis

Former à l'enseignement de l'étude de la langue Que nous disent les pratiques déclarées des professeurs d'école débutants ? (2010). In CDROM du colloque Enseigner la grammaire en Francophonie : curricula, pratiques observées, formation des enseignants. Toulouse, 16-18 février 2010.

Notre communication rend compte d'un volet de la recherche INRP " L'enseignement de la langue dans les plans de formation initiale des enseignants du premier degré : comparaison entre IUFM et pays de la Francophonie " (2007-2010) co-dirigée par C. Garcia-Debanc et V. Paolacci et menée à l'IUFM de Midi-Pyrénées-Ecole interne de Toulouse II Le Mirail. Elle concerne les enseignants débutants en formation initiale et leur rapport avec l'enseignement de l'étude de la langue. Quelles représentations se font les stagiaires de l'enseignement grammatical ? Comment sont déclinés les curricula par des professeurs des Ecoles en formation initiale ? Que peut-on dire du curriculum effectivement enseigné par ces enseignants entrant dans le métier

Extraction de termes, reconnaissance et labellisation de relations dans un th\'esaurus

Within the documentary system domain, the integration of thesauri for indexing and retrieval information steps is usual. In libraries, documents own rich descriptive information made by librarians, under descriptive notice based on Rameau thesaurus. We exploit two kinds of information in order to create a first semantic structure. A step of conceptualization allows us to define the various modules used to automatically build the semantic structure of the indexation work. Our current work focuses on an approach that aims to define an ontology based on a thesaurus. We hope to integrate new knowledge characterizing the territory of our structure (adding "toponyms" and links between concepts) thanks to a geographic information system (GIS)

Comment intégrer des logiciels issus de la recherche en EIAH ?

Cet article aborde le problème de la ré-utilisation, dans un but de recherche, de logiciels EIAH sous forme de prototypes ou d'environnements développés dans d'autres équipes de recherche. En nous appuyant sur des travaux traitant des problèmes d'interopérabilité et d'intégration, nous tentons d'illustrer cette problématique étudiée collectivement au sein de l'AS " Plates-formes technologiques pour la recherche en EIAH ". Après avoir analysé les besoins d'intégrer des logiciels EIAH pour construire une activité d'apprentissage, nous argumentons autour d'une proposition d'architecture d'intégration. Notre analyse des besoins débouche sur une présentation des différentes dimensions d'intégration possible. Au regard de ces dimensions d'intégration, nous présentons cinq études de cas issus de la communauté française. Nous concluons en proposant un guide des bonnes pratiques pour l'intégration

Simulation numérique de la condensation / évaporation et de la coagulation des nanoparticules

National audienceAware of the risks related to nanoparticles (particles which present at least one dimension less than 100 nanometers), INERIS decided in 2009 to create a research program in order to develop a model that would be able to simulate the dynamic of nanoparticles in both confined and free atmospheres. The distinction with usual models is that we need to follow the evolution of the number of particles together with their the mass : in order to simulate the evolution of nanoparticles, the number is much more relevant. A comparative review of algorithms currently used in air quality models and new algorithms adapted to nanoparticles is presented. This first study addresses condensational growth, evaporation and coagulation. The model is to be integrated in chemistry-transport models (CHIMERE) and in CFD models (code_Saturne EdF).Conscient des risques liés aux nanoparticules (particules dont au moins une des dimensions est inférieure à 100 nanomètres), l'INERIS(1) a engagé en 2009 un programme de recherche en collaboration avec le CEREA(2) afin de développer un modèle capable de simuler les transformations des nanoparticules dans les ambiances intérieures (espaces confinés) comme dans l'atmosphère. En effet, les nanoparticules sont notamment susceptibles de coaguler, de grossir par condensation, et de se déposer sur les parois; ce qui modifie leur granulométrie. Une des problématiques liée à la modélisation des nanoparticules est que leur nombre est déterminant devant leur masse, tout au contraire des particules étudiées jusqu'à présent (particules fines ou grossières dont une des dimensions est supérieure à 100 nanomètre). Différents schémas numériques ont été développés pour simuler la condensation/évaporation d'une population de particules, et un noyau de coagulation issu d'algorithmes usuels a été intégré. L'inter-comparaison de ces schémas met en évidence que certains sont plus adaptés que d'autres pour les nanoparticules. Les algorithmes qui sont appropriés pour toutes les tailles de particules sont présentés. A terme, ce modèle de dynamique des nanoparticules a vocation à être intégré dans des modèles de dispersion atmosphérique (CHIMERE) et des modèles CFD (code_Saturne EdF

On the impact of the vertical resolution on chemistry-transport modelling

International audienceThis paper presents a sensitivity analysis of the modelling of air pollutant concentrations in the surface layer with the WRF/CHIMERE models. The influence of the vertical resolution near the surface is studied. The simulations are carried out over two periods (winter and summer 2009) over the Paris area. Three model configurations are used: (i) the CHIMERE mesh used for the PREVAIR forecast (8 levels from 995 to 500 hPa), (ii) a mesh refined along the whole vertical axis (20 levels from 995 to 500 hPa) and (iii) a mesh with a refinement near the surface (9 levels from 999 to 500 hPa). The results are discussed in terms of differences on surface concentrations between the reference case and an improved resolution. Adding a point close to the surface appears to be important mainly for high nocturnal concentrations in very stable boundary layers. Refining the vertical mesh, with 20 levels instead of 8, enables to model new structures in the well mixed boundary layer, but with a moderate impact at the surface. It is shown that the different model configurations lead to changes of a few mu g m(-3) at most, showing that the vertical mesh is not the most sensitive factor in chemistry-transport modelling when results are compared to surface measurements. This finding validates the fact that a simplified vertical mesh is suitable for air quality forecasting even if an improved vertical resolution close to the ground is important to take into account the urban increment

Evolution de la surveillance des PM10 en France : épisodes de pollution par les particules au printemps 2007

National audienceSince the 1st January 2007, PM10 monitoring network in France has evolved, in order to account for volatile fraction of PM10. This evolution permitted the observation of high peaks of PM10 during spring 2007. Concentrations during these peaks would have been largely underestimated with measuring techniques used before 2007. A study, coupling chemical and modelling approach of the phenomenon has been launched by LCSQA (Laboratoire Central de Surveillance de la Qualité de l'Air), in collaboration with several AASQA (Association Agrée de Surveillance de la Qualité de l'Air, air monitoring network). Chemical analysis of PM10 show that ammonium nitrate is the component at the origin of the observed peaks. The French forecasting system for air quality Prév'Air (www.prevair.org) largely underestimated the peaks, and especially ammonium nitrate concentrations. A sensibility study shows that emissions due to agricultural practices seem to be at the origin of the peaks. The necessity of reconsidering these emissions as a function of meteorological conditions (especially the temperature) is highlightedDepuis le 1er janvier 2007, le dispositif de surveillance des PM10 en France a évolué, de façon à prendre en compte la fraction volatile des particules. Une conséquence de cette évolution est l'observation, au printemps 2007, d'importants pics de particules : ces pics auraient été largement sous-évalués avec les techniques précédemment utilisées. Le LCSQA (Laboratoire Central de Surveillance de la Qualité de l'Air), en collaboration avec plusieurs AASQA (Association Agrée de Surveillance de la Qualité de l'Air) a entrepris un travail de compréhension de l'origine des pics, couplant mesures de terrain et modélisation Les résultats expérimentaux montrent que, pour la plupart des pics étudiés, la fraction volatile est généralement supérieure à la fraction non-volatile. Des analyses chimiques ont permis de mettre en évidence la présence prépondérante du nitrate d'ammonium dans la plupart des cas, expliquant ponctuellement les larges fractions volatiles mesurées. Sur le plan de la modélisation, le modèle CHIMERE utilisé dans le système Prév'Air (www.prevair.org) a sous-estimé ces fortes concentrations, et en particulier les concentrations en nitrate d'ammonium. Les émissions d'espèces azotées lors des épandages massifs d'engrais à cette période de l'année, mal prises en compte, pourraient en grande partie expliquer les résultats. La nécessité de reconsidérer dans le modèle la dépendance de ces émissions aux conditions météorologiques (notamment les températures élevées qui favorisent l'évaporation) a été mise en évidenc

Impact of Surface Roughness and Soil Texture on Mineral Dust Emission Fluxes Modeling

Dust production models (DPM) used to estimate vertical fluxes of mineral dust aerosols over arid regions need accurate data on soil and surface properties. The Laboratoire Inter-Universitaire des Systemes Atmospheriques (LISA) data set was developed for Northern Africa, the Middle East, and East Asia. This regional data set was built through dedicated field campaigns and include, among others, the aerodynamic roughness length, the smooth roughness length of the erodible fraction of the surface, and the dry (undisturbed) soil size distribution. Recently, satellite-derived roughness length and high-resolution soil texture data sets at the global scale have emerged and provide the opportunity for the use of advanced schemes in global models. This paper analyzes the behavior of the ERS satellite-derived global roughness length and the State Soil Geographic data base-Food and Agriculture Organization of the United Nations (STATSGO-FAO) soil texture data set (based on wet techniques) using an advanced DPM in comparison to the LISA data set over Northern Africa and the Middle East. We explore the sensitivity of the drag partition scheme (a critical component of the DPM) and of the dust vertical fluxes (intensity and spatial patterns) to the roughness length and soil texture data sets. We also compare the use of the drag partition scheme to a widely used preferential source approach in global models. Idealized experiments with prescribed wind speeds show that the ERS and STATSGO-FAO data sets provide realistic spatial patterns of dust emission and friction velocity thresholds in the region. Finally, we evaluate a dust transport model for the period of March to July 2011 with observed aerosol optical depths from Aerosol Robotic Network sites. Results show that ERS and STATSGO-FAO provide realistic simulations in the region

Trace gas/aerosol boundary concentrations and their impacts on continental-scale AQMEII modeling domains

Copyright 2011 Elsevier B.V., All rights reserved.Over twenty modeling groups are participating in the Air Quality Model Evaluation International Initiative (AQMEII) in which a variety of mesoscale photochemical and aerosol air quality modeling systems are being applied to continental-scale domains in North America and Europe for 2006 full-year simulations for model inter-comparisons and evaluations. To better understand the reasons for differences in model results among these participating groups, each group was asked to use the same source of emissions and boundary concentration data for their simulations. This paper describes the development and application of the boundary concentration data for this AQMEII modeling exercise. The European project known as GEMS (Global and regional Earth-system Monitoring using Satellite and in-situ data) has produced global-scale re-analyses of air quality for several years, including 2006 (http://gems.ecmwf.int). The GEMS trace gas and aerosol data were made available at 3-hourly intervals on a regular latitude/longitude grid of approximately 1.9° resolution within 2 "cut-outs" from the global model domain. One cut-out was centered over North America and the other over Europe, covering sufficient spatial domain for each modeling group to extract the necessary time- and space-varying (horizontal and vertical) concentrations for their mesoscale model boundaries. Examples of the impact of these boundary concentrations on the AQMEII continental simulations are presented to quantify the sensitivity of the simulations to boundary concentrations. In addition, some participating groups were not able to use the GEMS data and instead relied upon other sources for their boundary concentration specifications. These are noted, and the contrasting impacts of other data sources for boundary data are presented. How one specifies four-dimensional boundary concentrations for mesoscale air quality simulations can have a profound impact on the model results, and hence, this aspect of data preparation must be performed with considerable care.Peer reviewedFinal Accepted Versio