Publications

2015

• Modeling of particle mixing in the atmosphere
  
  • Zhu Shupeng
  , 2015. This thesis present a newly developed size-composition resolved aerosol model (SCRAM), which is able to simulate the dynamics of externally-mixed particles in the atmosphere, and it evaluates its performance in three-dimensional air-quality simulations. The main work is split into four parts. First, the research context of external mixing and aerosol modelling is introduced. Secondly, the development of the SCRAM box model is presented along with validation tests. Each particle composition is defined by the combination of mass-fraction sections of its chemical components or aggregates of components. The three main processes involved in aerosol dynamic (nucleation, coagulation, condensation/evaporation) are included in SCRAM. The model is first validated by comparisons with published reference solutions for coagulation and condensation/evaporation of internally-mixed particles. The particle mixing state is investigated in a 0-D simulation using data representative of air pollution at a traffic site in Paris. The relative influence on the mixing state of the different aerosol processes and of the algorithm used to model condensation/evaporation (dynamic evolution or bulk equilibrium between particles and gas) is studied. Then, SCRAM is integrated into the Polyphemus air quality platform and used to conduct simulations over Greater Paris during the summer period of 2009. This evaluation showed that SCRAM gives satisfactory results for both PM2.5/PM10 concentrations and aerosol optical depths, as assessed from comparisons to observations. Besides, the model allows us to analyze the particle mixing state, as well as the impact of the mixing state assumption made in the modelling on particle formation, aerosols optical properties, and cloud condensation nuclei activation. Finally, two simulations are conducted during the winter campaign of MEGAPOLI (Megacities : Emissions, urban, regional and Global Atmospheric POLlution and climate effects, and Integrated tools for assessment and mitigation) in January 2010 where the composition of individual particles was measured. One simulation assumes that particles are internally mixed, while the other explicitly models the mixing state with SCRAM. The simulation results of both bulk concentrations of chemical species and concentrations of individual particle classes are compared with the measurements. Then, the single particle diversity and the mixing-state index are computed using a quantification approach based on information-theoretic entropy, and they are compared to those derived from the measurements at a urban site in Paris: the simulated mixing-state index is equal to 69% against 59% from the measurements, indicating that particles are not internally mixed over Paris (10.70675/a88c530bz1400z46dcz8e69z080b8a96ad7a)
  DOI : 10.70675/a88c530bz1400z46dcz8e69z080b8a96ad7a
• Ensemble forecast of solar radiation using TIGGE weather forecasts and HelioClim database
  
  • Thorey Jean
  • Mallet Vivien
  • Chaussin Christophe
  • Descamps Laurent
  • Blanc Philippe
  Solar Energy, Elsevier, 2015, 120, pp.232–243. Medium-range forecasts (one day to two weeks) of solar radiation are commonly assessed with a single forecast at a given location. In this paper, we forecast maps of surface solar irradiance, using ensembles of forecasts from the THORPEX Interactive Grand Global Ensemble (TIGGE) with a 6-h timestep. We compare our forecasts with observations derived from MeteoSat Second Generation (MSG) and provided by the HelioClim-3 database as gridded observations over metropolitan France. First, we study the ensembles from six meteorological centers. Second, we use sequential aggregation to linearly combine all the forecasts with weights that vary in space and time. Sequential aggregation updates the weights before any forecast, using available observations. We use the global numerical weather prediction from the European Center for Medium-range Weather Forecasts (ECMWF) as a reference forecast. The issue of spatial resolution is discussed because the low resolution forecasts from TIGGE are compared to high resolution irradiance estimated from MSG data. We found that the TIGGE ensembles are under-dispersed but rather different from one to another. Aggregation decreases the forecast error by 20%, and produces a more realistic spatial pattern of predicted irradiance. (10.1016/j.solener.2015.06.049)
  DOI : 10.1016/j.solener.2015.06.049
• Spatial variability, horizontal anisotropy and diurnal evolution of measured infra-red fluxes in a city neighborhood of Toulouse
  
  • Carissimo Bertrand
  • Qu Yongfeng
  • Bresson Raphaël
  • Daviau Noelie
  • Gaudio Noémie
  • Milliez Maya
  , 2015.
• Modélisation tridimensionnelle du rayonnement infrarouge atmosphérique utilisant l'approximation en émissivité : application à la formation du brouillard radiatif
  
  • Makke Laurent
  , 2015. Afin de modéliser l'absorption dans le traitement des transferts radiatifs en milieu atmosphérique, de nombreuses méthodes plus précises et plus rapides ont été développées. La modélisation de la formation du brouillard, où le rayonnement infrarouge joue un rôle très important, nécessite des méthodes numériques suffisamment précises pour calculer le taux de refroidissement. Le brouillard radatif se forme après des conditions de ciel clair, où l'absorption est le processus radiatif dominant, en raison d'un fort refroidissement nocturne. Avec l'augmentation des ressources de calcul et le développement du Calcul Haute Performance, les modèles à bandes, pour effectuer l'intégration sur la longueur des grandeurs radiométriques, sont les plus utilisés. Toutefois, le couplage entre les transferts radiatifs 3-D et la dynamique des fluides reste très coûteux en temps de calcul. Le rayonnement augmente d'environ cinquante pourcent le temps de la simulation pour la dynamique des fluides uniquement. Pour réduire le temps passé dans une itération radiative, une nouvelle paramétrization basée sur les modèles en émissivité a été développée. Cette approche nécessite seulement une résolution de l'ETR contre N_{bandes} x N_{gauss} pour un modèle à N_{bandes} avec N_{gauss} points de quadratures sur chaque bande. Une comparaison avec des données de simulation a été effectuée et cette nouvelle paramétrisation de l'absorption infrarouge a montré sa capacité à prendre en compte les variations des concentrations gazeuses et d'eau liquide. Une étude à travers le couplage entre le modèle développé et le code de CFD Code_Saturne a été réalisée afin valider dynamiquement notre paramétrisation. Enfin une simulation exploratoire a été effectuée sur un domaine 3-D en présence de bâti idéalisé, pour capter les effets radiatifs 3-D dûs aux hétérogénéités horizontales du champ d'eau liquide et des bâtiments (10.70675/fa85cd82z0608z4af2z9b60z77f6d249e997)
  DOI : 10.70675/fa85cd82z0608z4af2z9b60z77f6d249e997
• Urbanisme et qualité de l'air; des territoires qui respirent. Brochure ADEME.Connaître pour agir.
  
  • Benoît Bulliot
  • Thill Marion
  • Crohas Jean-Baptiste
  • Volokoff Aurélie
  • Evrard Benoït
  • Lepesant Benoît
  • Peyet Claire
  • Harpet Cyrille
  • Marseille Fabienne
  • Bretagne Geneviève
  • Coll Isabelle
  • Szerman Jacques
  • Muller-Perriand Karine
  • Cuzin Ysaline
  • Milliez Maya
  , 2015.
• ParisFog : observations brouillard au SIRTA et études de processus associées
  
  • Dupont Jean-Charles
  • Haeffelin Martial
  • Elias Thierry
  • Burnet Frédéric
  • Delanoë Julien
  • Musson-Genon Luc
  • Dupont E.
  • Sciare Jean
  • Crenn V.
  , 2015.
• Modelling atmospheric dry deposition in urban areas using an urban canopy approach
  
  • Chérin N.
  • Roustan Y.
  • Musson-Genon L.
  • Seigneur C.
  Geoscientific Model Development, European Geosciences Union, 2015, 8 (3), pp.893-910. Atmospheric dry deposition is typically modelled using an average roughness length, which depends on land use. This classical roughness-length approach cannot account for the spatial variability of dry deposition in complex settings such as urban areas. Urban canopy models have been developed to parametrise momentum and heat transfer. We extend this approach here to mass transfer, and a new dry deposition model based on the urban canyon concept is presented. It uses a local mixing-length parametrisation of turbulence within the canopy, and a description of the urban canopy via key parameters to provide spatially distributed dry deposition fluxes. Three different flow regimes are distinguished in the urban canyon depending on the height-to-width ratio of built areas: isolated roughness flow, wake interference flow and skimming flow. Differences between the classical roughness-length model and the model developed here are investigated. Sensitivity to key parameters are discussed. This approach provides spatially distributed dry deposition fluxes that depend on surfaces (streets, walls, roofs) and flow regimes (recirculation and ventilation) within the urban area. (10.5194/gmd-8-893-2015)
  DOI : 10.5194/gmd-8-893-2015
• Modelling chain for the effect of road traffic on air and water quality: Techniques, current status and future prospects
  
  • Fallah Shorshani Masoud
  • Andre Michel
  • Bonhomme Céline
  • Seigneur Christian
  Environmental Modelling and Software, Elsevier, 2015, 64, pp.pp. 102-123. Modelling approaches for simulating air and stormwater pollution due to on-road vehicles are reviewed and discussed. Models for traffic, emissions, atmospheric dispersion, and stormwater contamination are studied with particular emphasis on their couplings to create a modelling chain. The models must be carefully selected according to the requirements and level of detail of the integrated modelling chain. Although a fair amount of research has been conducted to link air pollution and road traffic, many questions related to spatio-temporal scales, domains of validity, consistency among models, un- certainties of model simulation results, and interfaces between models remain open. The aim of this work is to review the current status of the relationships between traffic, emissions, air quality, and water quality models, to recommend modelling approaches and to propose some directions for improving the state of the science. The difficulties and challenges associated with model coupling are illustrated with specific examples. (10.1016/j.envsoft.2014.11.020)
  DOI : 10.1016/j.envsoft.2014.11.020
• Atmospheric dispersion modeling near a roadway under calm meteorological conditions
  
  • Fallah Shorshani Masoud
  • Seigneur Christian
  • Polo Rehn Lucie
  • Chanut Hervé
  • Pellan Yann
  • Jaffrezo Jean-Luc
  • Charron Aurélie
  • Andre Michel
  Transportation Research Part D: Transport and Environment, Elsevier, 2015, 34, pp.pp. 137-154. Atmospheric pollutant dispersion near sources is typically simulated by Gaussian models because of their efficient compromise between reasonable accuracy and manageable com- putational time. However, the standard Gaussian dispersion formula applies downwind of a source under advective conditions with a well-defined wind direction and cannot calculate air pollutant concentrations under calm conditions with fluctuating wind direction and/or upwind of the emission source. Attempts have been made to address atmospheric disper- sion under such conditions. This work evaluates the performance of standard and modified Gaussian plume models using measurements of NO2, PM10, PM2.5, five inorganic ions and seven metals conducted near a freeway in Grenoble, France, during 11-27 September 2011. The formulation for calm conditions significantly improves model performance. However, it appears that atmospheric dispersion due to vehicle-induced turbulence is still underestimated. Furthermore, model performance is poor for particulate species unless road dust resuspension by traffic is explicitly taken into account. (10.1016/j.trd.2014.10.013)
  DOI : 10.1016/j.trd.2014.10.013
• Continental pollution in the western Mediterranean basin: vertical profiles of aerosol and trace gases measured over the sea during TRAQA 2012 and SAFMED 2013
  
  • Di Biagio Claudia
  • Doppler Lionel
  • Gaimoz Cécile
  • Grand Noël
  • Ancellet Gérard
  • Raut Jean-Christophe
  • Beekmann Matthias
  • Borbon Agnès
  • Sartelet Karine
  • Attié Jean-Luc
  • Ravetta François
  • Formenti Paola
  Atmospheric Chemistry and Physics, European Geosciences Union, 2015, 15 (16), pp.9611-9630. In this study we present airborne observations of aerosol and trace gases obtained over the sea in the Western Mediterranean Basin during the TRAQA (TRansport and Air QuAlity) and SAFMED (Secondary Aerosol Formation in the MEDiterranean) campaigns in summers 2012 and 2013. A total of 23 vertical profiles were measured up to 5000 m a.s.l. over an extended area (40–45° N latitude and 2° W–12° E longitude) including the Gulf of Genoa, Southern France, the Gulf of Lion, and the Spanish coast. TRAQA and SAFMED successfully measured a wide range of meteorological conditions which favoured the pollution export from different sources located around the basin. Also, several events of dust outflows were measured during the campaigns. Observations from the present study indicate that continental pollution largely affects the Western Mediterranean both close to coastal regions and in the open sea as far as ~250 km from the coastline. Aerosol layers not specifically linked with Saharan dust outflows are distributed ubiquitously which indicates quite elevated levels of background pollution throughout the Western Basin. The measured aerosol scattering coefficient varies between ~20 and 120 M m−1, while carbon monoxide (CO) and ozone (O3) mixing ratios are in the range of 60–170 and 30–85 ppbv, respectively. Pollution reaches 3000–4000 m in altitude and presents a very complex and highly stratified structure characterized by fresh and aged layers both in the boundary layer and in the free troposphere. Within pollution plumes the measured particle concentration in the Aitken (0.004–0.1 μm) and accumulation (0.1–1.0 μm) modes is between $\sim 100$ and 5000–6000 s cm−3 (standard cm−3), which is comparable to the aerosol concentration measured in continental urban areas. Additionally, our measurements indicate the presence of highly concentrated Aitken layers (10 000–15 000 s cm−3) observed both close to the surface and in the free troposphere, possibly linked to the influence of new particle formation (NPF) episodes over the basin. (10.5194/acp-15-9611-2015)
  DOI : 10.5194/acp-15-9611-2015
• Modelling of the atmospheric dispersion of mercury emitted from the power sector in Poland
  
  • Zysk J.
  • Roustan Y.
  • Wyrwa A.
  Atmospheric Environment, Elsevier, 2015, 112, pp.246-256. Poland belongs to the group of EU countries with the highest levels of mercury emissions, with a large portion of these emissions being related to coal combustion. This paper presents a modelling analysis of the impact that the Polish power sector has on the atmospheric concentrations of mercury. A detailed mercury emission inventory is used to analyse the concentration and deposition of mercury. For this study, a chemical scheme devoted to mercury transformations in the atmosphere was implemented into the Polyphemus air quality system. The system was then used to perform simulations for 2008 in two domains i.e. over Europe and over Poland. The impact of various parameters on concentration and wet scavenging of mercury has been analysed. The results of the mercury ambient concentrations and depositions, are presented. Additionally, the contribution of natural and anthropogenic sources to mercury deposition in Poland is shown. The performed works showed that the national sources have low impact to overall deposition, however local contribution in wet deposition of big emitters may reach 50%. Sensitive analysis showed a significant impact of reaction with bromine compound and scavenging coefficient on modelled results of mercury concentration and deposition. (C) 2015 Elsevier Ltd. All rights reserved. (10.1016/j.atmosenv.2015.04.040)
  DOI : 10.1016/j.atmosenv.2015.04.040
• Assessment of source contributions to air pollution in Beirut, Lebanon: a comparison of source-based and tracer-based modeling approaches
  
  • Waked A.
  • Afif C.
  • Seigneur C.
  Air Quality, Atmosphere & Health, Springer, 2015, 8 (5), pp.495-505. A chemical-transport model (CTM), Polyphemus/Polair3D, is used to investigate the contributions of various anthropogenic and biogenic sources to total organic carbon (OC) in PM2.5 in Beirut, Lebanon, during the summer of 2011. Those results are compared to a tracer-based source apportionment of OC at an ambient site in Beirut where a measurement campaign was conducted in July 2011. The results obtained from the CTM in the base simulation S1 suggest contributions to total simulated OC mass (3.24 mu g/m(3)) of 66 % (2.14 +/- 1.07 mu g/m(3)) from fossil fuel burning (FFB) and 8 % (0.27 +/- 0.135 mu g/m(3)) from biogenic secondary organic carbon (BSOC). The tracer-based approach leads to contribution estimates to total measured OC mass (5.6 mu g/m(3)) of 16 % (0.9 mu g/m(3) +/- 0.22) from FFB, 53 % (2.9 +/- 1.7 mu g/m(3)) from BSOC, and 32 % (1.8 +/- 0.88 mu g/m(3)) from cooking activities. In a second CTM simulation S2, emissions related to cooking activities were added to the emission inventory, monoterpene and sesquiterpene secondary organic aerosol (SOA) surrogate species were added to the boundary conditions, and a lower ratio of semi-volatile organic compounds to primary organic aerosols (SVOC/POA) was used. The S2 results obtained showed contributions to total simulated OC mass (3.01 mu g/m(3)) of 33 % (0.98 +/- 0.49 mu g/m(3)) from FFB, 18 % (0.53 +/- 0.27 mu g/m(3)) from BSOC, and 39 % (1.2 +/- 0.6 mu g/m(3)) from cooking activities. The differences between these two methods are discussed in terms of their uncertainties and biases. The comparison of both approaches showed that the model underestimates the secondary fraction of OC, which may be due to underestimations of some biogenic volatile organic compound (VOC) emissions and/or boundary concentrations as well as the use of SOA yields that may not be representative of the eastern Mediterranean region. Concerning the tracer-based approach, the use of tracer/OC ratios that are not specific to Lebanon because of a lack of data could represent a limitation of this methodology. Nevertheless, this comparative analysis suggests that on-road transportation and diesel generators used for electricity production are major sources of atmospheric PM and should be targeted for emission reduction. Finally, cooking activities, which were identified as a significant source of PM with the tracer-based approach, should be studied further. (10.1007/s11869-014-0298-z)
  DOI : 10.1007/s11869-014-0298-z
• The Secondary Organic Aerosol Processor (SOAP v1.0) model: a unified model with different ranges of complexity based on the molecular surrogate approach
  
  • Couvidat F.
  • Sartelet K.
  Geoscientific Model Development, European Geosciences Union, 2015, 8 (4), pp.1111-1138. In this paper the Secondary Organic Aerosol Processor (SOAP v1.0) model is presented. This model determines the partitioning of organic compounds between the gas and particle phases. It is designed to be modular with different user options depending on the computation time and the complexity required by the user. This model is based on the molecular surrogate approach, in which each surrogate compound is associated with a molecular structure to estimate some properties and parameters (hygroscopicity, absorption into the aqueous phase of particles, activity coefficients and phase separation). Each surrogate can be hydrophilic (condenses only into the aqueous phase of particles), hydrophobic (condenses only into the organic phases of particles) or both (condenses into both the aqueous and the organic phases of particles). Activity coefficients are computed with the UNIFAC (UNI-versal Functional group Activity Coefficient; Fredenslund et al., 1975) thermodynamic model for short-range interactions and with the Aerosol Inorganic-Organic Mixtures Functional groups Activity Coefficients (AIOMFAC) parameterization for medium-and long-range interactions between electrolytes and organic compounds. Phase separation is determined by Gibbs energy minimization. The user can choose between an equilibrium representation and a dynamic representation of organic aerosols (OAs). In the equilibrium representation, compounds in the particle phase are assumed to be at equilibrium with the gas phase. However, recent studies show that the organic aerosol is not at equilibrium with the gas phase because the organic phases could be semi-solid (very viscous liquid phase). The condensation-evaporation of organic compounds could then be limited by the diffusion in the organic phases due to the high viscosity. An implicit dynamic representation of secondary organic aerosols (SOAs) is available in SOAP with OAs divided into layers, the first layer being at the center of the particle (slowly reaches equilibrium) and the final layer being near the interface with the gas phase (quickly reaches equilibrium). Although this dynamic implicit representation is a simplified approach to model condensation-evaporation with a low number of layers and short CPU (central processing unit) time, it shows good agreements with an explicit representation of condensation-evaporation (no significant differences after a few hours of condensation). (10.5194/gmd-8-1111-2015)
  DOI : 10.5194/gmd-8-1111-2015
• Data assimilation in atmospheric chemistry models: Current status and future prospects for coupled chemistry meteorology models
  
  • Bocquet Marc
  • Elbern H.
  • Eskes H.
  • Hirtl M.
  • Aabkar R.
  • Carmichael G. R.
  • Flemming J.
  • Inness A.
  • Pagowski M.
  • Pérez Camaño J. L.
  • Saide P. E.
  • San Jose R.
  • Sofiev M.
  • Vira J.
  • Baklanov A.
  • Carnevale C.
  • Grell G.
  • Seigneur C.
  Atmospheric Chemistry and Physics, European Geosciences Union, 2015, 15 (10), pp.5325-5358. Data assimilation is used in atmospheric chemistry models to improve air quality forecasts, construct re-analyses of three-dimensional chemical (including aerosol) concentrations and perform inverse modeling of input variables or model parameters (e.g., emissions). Coupled chemistry meteorology models (CCMM) are atmospheric chemistry models that simulate meteorological processes and chemical transformations jointly. They offer the possibility to assimilate both meteorological and chemical data; however, because CCMM are fairly recent, data assimilation in CCMM has been limited to date. We review here the current status of data assimilation in atmospheric chemistry models with a particular focus on future prospects for data assimilation in CCMM. We first review the methods available for data assimilation in atmospheric models, including variational methods, ensemble Kalman filters, and hybrid methods. Next, we review past applications that have included chemical data assimilation in chemical transport models (CTM) and in CCMM. Observational data sets available for chemical data assimilation are described, including surface data, surface-based remote sensing, airborne data, and satellite data. Several case studies of chemical data assimilation in CCMM are presented to highlight the benefits obtained by assimilating chemical data in CCMM. A case study of data assimilation to constrain emissions is also presented. There are few examples to date of joint meteorological and chemical data assimilation in CCMM and potential difficulties associated with data assimilation in CCMM are discussed. As the number of variables being assimilated increases, it is essential to characterize correctly the errors; in particular, the specification of error cross-correlations may be problematic. In some cases, offline diagnostics are necessary to ensure that data assimilation can truly improve model performance. However, the main challenge is likely to be the paucity of chemical data available for assimilation in CCMM. © Author(s) 2015. CC Attribution 3.0 License. (10.5194/acp-15-5325-2015)
  DOI : 10.5194/acp-15-5325-2015
• Expanding the validity of the ensemble Kalman filter without the intrinsic need for inflation
  
  • Bocquet Marc
  • Raanes P. N.
  • Hannart A.
  Nonlinear Processes in Geophysics, European Geosciences Union (EGU), 2015, 22 (6), pp.645-662. The ensemble Kalman filter (EnKF) is a powerful data assimilation method meant for high-dimensional nonlinear systems. But its implementation requires somewhat ad hoc procedures such as localization and inflation. The recently developed finite-size ensemble Kalman filter (EnKF-N) does not require multiplicative inflation meant to counteract sampling errors. Aside from the practical interest in avoiding the tuning of inflation in perfect model data assimilation experiments, it also offers theoretical insights and a unique perspective on the EnKF. Here, we revisit, clarify and correct several key points of the EnKF-N derivation. This simplifies the use of the method, and expands its validity. The EnKF is shown to not only rely on the observations and the forecast ensemble, but also on an implicit prior assumption, termed hyperprior, that fills in the gap of missing information. In the EnKF-N framework, this assumption is made explicit through a Bayesian hierarchy. This hyperprior has so far been chosen to be the uninformative Jeffreys prior. Here, this choice is revisited to improve the performance of the EnKF-N in the regime where the analysis is strongly dominated by the prior. Moreover, it is shown that the EnKF-N can be extended with a normal-inverse Wishart informative hyperprior that introduces additional information on error statistics. This can be identified as a hybrid EnKF-3D-Var counterpart to the EnKF-N. © Author(s) 2015. (10.5194/npg-22-645-2015)
  DOI : 10.5194/npg-22-645-2015
• Hints to discriminate the choice of wet deposition models applied to an accidental radioactive release
  
  • Quérel Arnaud
  • Roustan Yelva
  • Quelo Denis
  • Benoit Jean Pierre
  International Journal of Environment and Pollution, Inderscience, 2015, 58 (4), pp.268 - 279. In nuclear emergency management, wet deposition modelling is of crucial importance for correctly evaluating soil contamination after an atmospheric release. Wet deposition is generally divided into two main processes: in-cloud scavenging (rainout) and below-cloud scavenging (washout). The large number of schemes proposed in the literature for both processes reflects the uncertainties in our current understanding of these phenomena. There is presently no scientific consensus to discriminate between the two processes. In order to improve our understanding of the magnitude of modelling uncertainties, a comprehensive sensitivity analysis was performed by focusing on representation of wet deposition fluxes. A large number of model configurations involving different deposition schemes and modelling options were evaluated by comparison with available observations of soil contamination. The objective is to establish a priority rank order of wet deposition schemes for soil contamination modelling. (10.1504/IJEP.2015.077457)
  DOI : 10.1504/IJEP.2015.077457
• Decadal simulation and comprehensive evaluation of CESM/CAM5.1 with advanced chemistry, aerosol microphysics, and aerosol-cloud interactions
  
  • He J.
  • Zhang Y.
  • Glotfelty T.
  • He R. Y.
  • Bennartz R.
  • Rausch J.
  • Sartelet K.
  Journal of Advances in Modeling Earth Systems, American Geophysical Union, 2015, 7 (1), pp.110-141. Earth system models have been used for climate predictions in recent years due to their capabilities to include biogeochemical cycles, human impacts, as well as coupled and interactive representations of Earth system components (e.g., atmosphere, ocean, land, and sea ice). In this work, the Community Earth System Model (CESM) with advanced chemistry and aerosol treatments, referred to as CESM-NCSU, is applied for decadal (2001-2010) global climate predictions. A comprehensive evaluation is performed focusing on the atmospheric component-the Community Atmosphere Model version 5.1 (CAM5.1) by comparing simulation results with observations/reanalysis data and CESM ensemble simulations from the Coupled Model Intercomparison Project phase 5 (CMIP5). The improved model can predict most meteorological and radiative variables relatively well with normalized mean biases (NMBs) of -14.1 to -9.7% and 0.7-10.8%, respectively, although temperature at 2 m (T2) is slightly underpredicted. Cloud variables such as cloud fraction (CF) and precipitating water vapor (PWV) are well predicted, with NMBs of -10.5 to 0.4%, whereas cloud condensation nuclei (CCN), cloud liquid water path (LWP), and cloud optical thickness (COT) are moderately-to-largely underpredicted, with NMBs of -82.2 to -31.2%, and cloud droplet number concentration (CDNC) is overpredictd by 26.7%. These biases indicate the limitations and uncertainties associated with cloud microphysics (e.g., resolved clouds and subgrid-scale cumulus clouds). Chemical concentrations over the continental U.S. (CONUS) (e.g., SO42-, Cl-, OC, and PM2.5) are reasonably well predicted with NMBs of -12.8 to -1.18%. Concentrations of SO2, SO42-, and PM10 are also reasonably well predicted over Europe with NMBs of -20.8 to -5.2%, so are predictions of SO2 concentrations over the East Asia with an NMB of -18.2%, and the tropospheric ozone residual (TOR) over the globe with an NMB of -3.5%. Most meteorological and radiative variables predicted by CESM-NCSU agree well overall with those predicted by CESM-CMIP5. The performance of LWP and AOD predicted by CESM-NCSU is better than that of CESM-CMIP5 in terms of model bias and correlation coefficients. Large biases for some chemical predictions can be attributed to uncertainties in the emissions of precursor gases (e.g., SO2, NH3, and NOx) and primary aerosols (black carbon and primary organic matter) as well as uncertainties in formulations of some model components (e.g., online dust and sea-salt emissions, secondary organic aerosol formation, and cloud microphysics). Comparisons of CESM simulation with baseline emissions and 20% of anthropogenic emissions from the baseline emissions indicate that anthropogenic gas and aerosol species can decrease downwelling shortwave radiation (FSDS) by 4.7 W m(-2) (or by 2.9%) and increase SWCF by 3.2 W m(-2) (or by 3.1%) in the global mean. (10.1002/2014ms000360)
  DOI : 10.1002/2014ms000360
• Modelling atmospheric effects on performance and plume dispersal from natural draft wet cooling towers
  
  • Chahine A.
  • Matharan P.
  • Wendum D.
  • Musson-Genon L.
  • Bresson R.
  • Carissimo B.
  Journal of Wind Engineering and Industrial Aerodynamics, Elsevier, 2015, 136. (10.1016/j.jweia.2014.11.007)
  DOI : 10.1016/j.jweia.2014.11.007
• Plume-in-grid model for the evaluation of particulate matter contribution of industrial point and volume sources: application to refinery sources in the Paris region
  
  • Raffort Valentin
  • Kim Youngseob
  • Donnat Ludovic
  • Juery Catherine
  • Seigneur Christian
  • Duclaux Olivier
  International Journal of Environment and Pollution, Inderscience, 2015, 57 (3/4), pp.238. (10.1504/ijep.2015.074508)
  DOI : 10.1504/ijep.2015.074508
• A size-composition resolved aerosol model for simulating the dynamics of externally mixed particles: SCRAM (v 1.0)
  
  • Zhu S.
  • Sartelet K. N.
  • Seigneur C.
  Geoscientific Model Development, European Geosciences Union, 2015, 8 (6), pp.1595-1612. The Size-Composition Resolved Aerosol Model (SCRAM) for simulating the dynamics of externally mixed atmospheric particles is presented. This new model classifies aerosols by both composition and size, based on a comprehensive combination of all chemical species and their mass-fraction sections. All three main processes involved in aerosol dynamics (coagulation, condensation/evaporation and nucleation) are included. The model is first validated by comparison with a reference solution and with results of simulations using internally mixed particles. The degree of mixing of particles is investigated in a box model simulation using data representative of air pollution in Greater Paris. The relative influence on the mixing state of the different aerosol processes (condensation/evaporation, coagulation) and of the algorithm used to model condensation/evaporation (bulk equilibrium, dynamic) is studied. © 2015 Author(s). (10.5194/gmd-8-1595-2015)
  DOI : 10.5194/gmd-8-1595-2015
• Influence of an urban canopy model and PBL schemes on vertical mixing for air quality modeling over Greater Paris
  
  • Kim Youngseob
  • Sartelet Karine
  • Raut Jean-Christophe
  • Chazette Patrick
  Atmospheric Environment, Elsevier, 2015, 107, pp.289-306. Impacts of meteorological modeling in the planetary boundary layer (PBL) and urban canopy model (UCM) on the vertical mixing of pollutants are studied. Concentrations of gaseous chemical species, including ozone (O₃) and nitrogen dioxide (NO₂), and particulate matter over Paris and the near suburbs are simulated using the 3-dimensional chemistry-transport model Polair3D of the Polyphemus platform. Simulated concentrations of O₃, NO₂ and PM10/PM2.5 (particulate matter of aerodynamic diameter lower than 10 μm/2.5 μm, respectively) are first evaluated using ground measurements. Higher surface concentrations are obtained for PM10, PM2.5 and NO₂ with the MYNN PBL scheme than the YSU PBL scheme because of lower PBL heights in the MYNN scheme. Differences between simulations using different PBL schemes are lower than differences between simulations with and without the UCM and the Corine land-use over urban areas. Regarding the root mean square error, the simulations using the UCM and the Corine land-use tend to perform better than the simulations without it. At urban stations, the PM10 and PM2.5 concentrations are over-estimated and the over-estimation is reduced using the UCM and the Corine land-use. The ability of the model to reproduce vertical mixing is evaluated using NO₂ measurement data at the upper air observation station of the Eiffel Tower, and measurement data at a ground station near the Eiffel Tower. Although NO₂ is under-estimated in all simulations, vertical mixing is greatly improved when using the UCM and the Corine land-use. Comparisons of the modeled PM10 vertical distributions to distributions deduced from surface and mobile lidar measurements are performed. The use of the UCM and the Corine land-use is crucial to accurately model PM10 concentrations during nighttime in the center of Paris. In the nocturnal stable boundary layer, PM10 is relatively well modeled, although it is over-estimated on 24 May and under-estimated on 25 May. However, PM10 is under-estimated on both days in the residual layer, and over-estimated on both days over the residual layer. The under-estimations in the residual layer are partly due to difficulties to estimate the PBL height, to an over-estimation of vertical mixing during nighttime at high altitudes and to uncertainties in PM10 emissions. The PBL schemes and the UCM influence the PM vertical distributions not only because they influence vertical mixing (PBL height and eddy-diffusion coefficient), but also horizontal wind fields and humidity. However, for the UCM, it is the influence on vertical mixing that impacts the most the PM10 vertical distribution below 1.5 km. (10.1016/j.atmosenv.2015.02.011)
  DOI : 10.1016/j.atmosenv.2015.02.011