Publications

2014

• Representation and evaluation of wildfire propagation simulations
  
  • Filippi Jean-Baptiste
  • Mallet Vivien
  • Nader Bahaa
  International Journal of Wildland Fire, CSIRO Publishing, 2014, 23 (1), pp.46-57. This paper provides a formal mathematical representation of a wildfire simulation, reviews the most common scoring methods using this formalism, and proposes new methods that are explicitly designed to evaluate a forest fire simulation from ignition to extinction. These scoring or agreement methods are tested with synthetic cases in order to expose strengths and weaknesses, and with more complex fire simulations using real observations. An implementation of the methods is provided as well as an overview of the software package. The paper stresses the importance of scores that can evaluate the dynamics of a simulation, as opposed to methods relying on snapshots of the burned surfaces computed by the model. The two new methods, arrival time agreement and shape agreement, take into account the dynamics of the simulation between observation times. Although no scoring method is able to perfectly synthesise a simulation error in a single number, the analysis of the scores obtained on idealised and real simulations provides insights into the advantages of these methods for the evaluation of fire dynamics. (10.1071/WF12202)
  DOI : 10.1071/WF12202
• Développement et évaluation d'un modèle d'aérosols résolu en taille et en composition chimique pour une meilleure représentation de la pollution particulaire à l'échelle urbaine avec le modèle de Chimie Transport CHIMERE
  
  • Debry Edouard
  • Couvidat Florian
  • Bessagnet Bertrand
  • Rouil Laurence
  , 2014.
• Modélisation et évaluation de l’oligomérisation
  
  • Lemaire Vincent
  • Coll Isabelle
  • Couvidat Florian
  • Bessagnet Bertrand
  • Seigneur Christian
  , 2014.
• Fukushima : de la radioactivité dans l'air
  
  • Winiarek Victor
  • Bocquet Marc
  , 2014. No abstract.
• Quand modèles numériques et mesures ne sont pas sur la même longueur d'onde
  
  • Bocquet Marc
  • Koohkan Mohammad Reza
  , 2014. No abstract.
• Image-based modelling of ocean surface circulation from satellite acquisitions
  
  • Béréziat Dominique
  • Herlin Isabelle
  , 2014, pp.288-295. Satellite image sequences permit to visualise oceans' surface and their underlying dynamics. Processing these images is then of major interest in order to better understanding of the observed processes. As demonstrated by state-of-the-art, image assimilation allows to retrieve surface motion from image sequences, based on assumptions on the dynamics. In this paper we demonstrate that a simple heuristics, such as the Lagrangian constancy of velocity, can be used, and successfully replaces the complex physical properties described by the Navier-Stokes equations, for assessing surface circulation from satellite images. A data assimilation method is proposed that includes an additional term a(t) to this Lagrangian constancy equation. That term summarises all physical processes other than advection. A cost function is designed, which quantifies discrepancy between satellite data and model values. The cost function is minimised by the BFGS solver with a dual method of data assimilation. The result is the motion field and the additional term a(t). This last component models the forces, other than advection, that contribute to surface circulation. The approach has been tested on Sea Surface Temperature of Black Sea. Results are given on four image sequences and compared with state-of-the-art methods. (10.5220/0004669602880295)
  DOI : 10.5220/0004669602880295
• Estimation of the caesium-137 source term from the Fukushima Daiichi nuclear power plant using a consistent joint assimilation of air concentration and deposition observations
  
  • Winiarek Victor
  • Bocquet Marc
  • Duhanyan Nora
  • Roustan Yelva
  • Saunier Olivier
  • Mathieu Anne
  Atmospheric Environment, Elsevier, 2014, 82, pp.268-279. Inverse modelling techniques can be used to estimate the amount of radionuclides and the temporal profile of the source term released in the atmosphere during the accident of the Fukushima Daiichi nuclear power plant in March 2011. In Winiarek et al. (2012b), the lower bounds of the caesium-137 and iodine-131 source terms were estimated with such techniques, using activity concentration measurements. The importance of an objective assessment of prior errors (the observation errors and the background errors) was emphasised for a reliable inversion. In such critical context where the meteorological conditions can make the source term partly unobservable and where only a few observations are available, such prior estimation techniques are mandatory, the retrieved source term being very sensitive to this estimation. We propose to extend the use of these techniques to the estimation of prior errors when assimilating observations from several data sets. The aim is to compute an estimate of the caesium-137 source term jointly using all available data about this radionuclide, such as activity concentrations in the air, but also daily fallout measurements and total cumulated fallout measurements. It is crucial to properly and simultaneously estimate the background errors and the prior errors relative to each data set. A proper estimation of prior errors is also a necessary condition to reliably estimate the a posteriori uncertainty of the estimated source term. Using such techniques, we retrieve a total released quantity of caesium-137 in the interval 11.6 − 19.3 PBq with an estimated standard deviation range of 15 − 20% depending on the method and the data sets. The "blind" time intervals of the source term have also been strongly mitigated compared to the first estimations with only activity concentration data. (10.1016/j.atmosenv.2013.10.017)
  DOI : 10.1016/j.atmosenv.2013.10.017
• Cost Action Es1006. Evaluation, improvement and guidance of local-scale emergency prediction and response tools for airborne hazards in built environments: Ongoing activities, experiments and recent results
  
  • Gariazzo C.
  • Leitl B.
  • Castelli S.
  • Baumann-Stanzer K.
  • Reisin T. G.
  • Barmpas F.
  • Tinarelli G.
  • Milliez C. M.
  • Bemporad E.
  • Armand P.
  Chemical Engineering Transactions, AIDIC [2002-....], 2014, 36, pp.529-534. The COST Action ES1006 is mainly aimed at evaluating and improving the reliability of neighbourhoodscale emergency response tools on the basis of a comprehensive, concerted and harmonized crossnational approach. The main focus is the evaluation of the air dispersion models, when used in urban or industrial environments with complex building structures, and their integration in emergency response systems. In the frame of this research, three working groups are carrying out several activities such as: to inventory models, tools and methodologies currently applied in the context of emergency management and local-scale threat reduction; to categorize and characterize local-scale threat scenarios; to identify the main gaps, deficiencies and limitations in presently available knowledge and models and to determine the directions for the development of the next generation of models; to test and evaluate available models by model inter-comparison and by comparison against test data from qualified field and laboratory experiments. The ongoing activities in the three WGs and the latest available results will be presented. © Copyright 2014, AIDIC Servizi S.r.l. (10.3303/cet1436089)
  DOI : 10.3303/cet1436089
• Development of a plume-in-grid model for industrial point and volume sources: application to power plant and refinery sources in the Paris region
  
  • Kim Y.
  • Seigneur C.
  • Duclaux O.
  Geoscientific Model Development, European Geosciences Union, 2014, 7 (2), pp.569-585. Plume-in-grid (PinG) models incorporating a host Eulerian model and a subgrid-scale model (usually a Gaussian plume or puff model) have been used for the simulations of stack emissions (e.g., fossil fuel-fired power plants and cement plants) for gaseous and particulate species such as nitrogen oxides (NOx), sulfur dioxide (SO2), particulate matter (PM) and mercury (Hg). Here, we describe the extension of a PinG model to study the impact of an oil refinery where volatile organic compound (VOC) emissions can be important. The model is based on a reactive PinG model for ozone (O3), which incorporates a three-dimensional (3-D) Eulerian model and a Gaussian puff model. The model is extended to treat PM, with treatments of aerosol chemistry, particle size distribution, and the formation of secondary aerosols, which are consistent in both the 3-D Eulerian host model and the Gaussian puff model. Furthermore, the PinG model is extended to include the treatment of volume sources to simulate fugitive VOC emissions. The new PinG model is evaluated over Greater Paris during July 2009. Model performance is satisfactory for O3, PM2.5 and most PM2.5 components. Two industrial sources, a coal-fired power plant and an oil refinery, are simulated with the PinG model. The characteristics of the sources (stack height and diameter, exhaust temperature and velocity) govern the surface concentrations of primary pollutants (NOx, SO2 and VOC). O3 concentrations are impacted differently near the power plant than near the refinery, because of the presence of VOC emissions at the latter. The formation of sulfate is influenced by both the dispersion of SO2 and the oxidant concentration; however, the former tends to dominate in the simulations presented here. The impact of PinG modeling on the formation of secondary organic aerosol (SOA) is small and results mostly from the effect of different oxidant concentrations on biogenic SOA formation. The investigation of the criteria for injecting plumes into the host model (fixed travel time and/or puff size) shows that a size-based criterion is recommended to treat the formation of secondary aerosols (sulfate, nitrate, and ammonium), in particular, farther downwind of the sources (beyond about 15 km). The impacts of PinG modeling are less significant in a simulation with a coarse grid size (10 km) than with a fine grid size (2 km), because the concentrations of the species emitted from the PinG sources are relatively less important compared to background concentrations when injected into the host model with a coarser grid size. (10.5194/gmd-7-569-2014)
  DOI : 10.5194/gmd-7-569-2014
• Evaluation of a Plume-in-Grid Model for Line Sources with a Multiple Roadway Case Study
  
  • Briant Régis
  • Seigneur Christian
  Air Pollution Modeling and its Application XXII, 2014, pp.669-673. (10.1007/978-94-007-5577-2_114)
  DOI : 10.1007/978-94-007-5577-2_114
• Effect of Atmospheric Stability on the Atmospheric Dispersion Conditions Over a Industrial Site Surrounded by Forests
  
  • Zaïdi Hanane
  • Dupont Eric
  • Milliez Maya
  • Carissimo Bertrand
  • Musson-Genon Luc
  Air Pollution Modeling and its Application XXII, 2014, pp.733-737. (10.1007/978-94-007-5577-2_124)
  DOI : 10.1007/978-94-007-5577-2_124
• Searching for the distinctive signature of a city in atmospheric modelling: Could the Multi-Resolution Analysis (MRA) provide the DNA of a city?
  
  • Mouzourides P.
  • Kyprianou A.
  • Brown M. J.
  • Carissimo B.
  • Choudhary R.
  • Neophytou M. K. A.
  Urban Climate, Elsevier, 2014, 10 (P2), pp.447-475. Mesoscale meteorological models rely on urban building datasets in order to determine several urban canopy parameters, such as the urban surface cover and morphological parameters, for accurate predictions of air quality and atmospheric pollution dispersion. Due to the multi-scale nature of air pollution dispersion, such models are run at various resolutions, and therefore grid sizes, in order to reflect the scale of observation and desired outputs. In this paper, a novel methodology, the Multi-Resolution Analysis (MRA), is applied to the urban building datasets of a number of European and North-American cities in order to obtain rigorously scale-adaptive spatially-varying representations of the different urban datasets.In the context of MRA, the urban-building information signal is analysed at different levels that each corresponds to a different scale. At each level the urban signal depicting a city is decomposed into an approximation, a representation at the scale that corresponds to the level, and a detail that is the part removed from the previous level that corresponds to lower scale. One of the major capacities and outputs of the MRA application is the multi-scale representation of the urban information while not losing the ability to recover the original density of urban information due to the tracking of the details. In this paper the results of such an MRA analysis of urban building datasets of European cities (London, Marseille and Nicosia) and North-American cities (New York City, Phoenix and Seattle as well as Oklahoma) are presented; the analysis provides consistent gridded and scaled attributes as well as sub-grid information for a hierarchy of grid sizes, for example used in nested urban simulations. Moreover, through the rigorous scale-adaptive spatially-varying representations that are obtained, a sound basis for consistent inter-comparisons is enabled. Finally, the paper illustrates how the MRA can provide an innovative means to perform analyses and provide unique scale-adaptive descriptions of any urban area - in essence a DNA-like description of a city. © 2014 Elsevier B.V. (10.1016/j.uclim.2014.04.001)
  DOI : 10.1016/j.uclim.2014.04.001
• A statistical method to estimate PM2.5 concentrations from meteorology and its application to the effect of climate change
  
  • Lecoeur E.
  • Seigneur C.
  • Pagé C.
  • Terray L.
  Journal of Geophysical Research: Atmospheres, American Geophysical Union, 2014, 119 (6), pp.3537-3585. A statistical algorithm was developed to estimate PM2.5 concentrations over Europe based on a weather-type representation of the meteorology. We used modeled PM2.5 concentrations as pseudoobservations, because of a lack of PM2.5 speciated measurements over Europe, and included four meteorological variables. This algorithm was evaluated on the learning period (2000-2008) to test its ability to reproduce the pseudoobserved data set and then applied for two climatological scenarios (RCP4.5 and RCP8.5) and one historical (1975-2004) and two future periods (2020-2049 and 2070-2099). In Italy, Poland, and northern, eastern, and southeastern Europe, all future scenarios lead to decreases in PM2.5, whereas in the Balkans, Benelux, the UK, and northern France, they lead to increases in PM2.5. Considering each season separately shows stronger responses, which may vary for a given region and scenario. Decomposing the changes in PM2.5 concentrations as the sum of intertype and intratype changes, and a residual term shows that (1) the residual term is negligible; (2) intertype changes affect more the regions along the Atlantic Ocean; and (3) in most other regions, intertype and intratype changes are often on the same order of magnitude. The relationship between the atmospheric circulation and weather types evolves and therefore modifies the mean of meteorological variables and PM2.5 concentrations. This algorithm offers a novel approach to investigate the effect of climate change on air quality and can be applied to other pollutants, regions, and meteorological models. Furthermore, this approach can be applied using actual speciated PM2.5 observations, if a sufficiently dense monitoring network were available. (10.1002/2013jd021172)
  DOI : 10.1002/2013jd021172
• A preliminary analysis of measurements from a near-field pollutants dispersion campaign in a stratified surface layer
  
  • Wei Xiao
  • Dupont Eric
  • Carissimo Bertrand
  • Gilbert Eric
  • Genon Luc Musson
  International Journal of Environment and Pollution, Inderscience, 2014, 55 (1/2/3/4), pp.184-191. In order to study pollutants dispersion in a stably stratified surface layer at small scales, a pollutants dispersion field experiment programme is being conducted on the site SIRTA in the southern suburb of Paris. In a preliminary campaign held during the winter of 2012 with continuous gas releases, we had 12 ultrasonic anemometers measuring wind velocity and temperature at 10 Hz, and six photo-ionisation detectors measuring gas concentration at 50 Hz. Turbulence is verified to be anisotropic by calculating variances, integral length scales and power spectra of velocity. Some evidence of a −1 power law sub-range has been found in velocity power spectra. Also, we have deduced eddy advection velocity from spatial velocity cross-correlation and found it greater than mean wind speed measured directly by sensors. Concentration measurements are corrected by using a baseline method. Significant relationships between concentration and turbulence measurements at high frequency are still under further study. (10.1504/IJEP.2014.065923)
  DOI : 10.1504/IJEP.2014.065923
• Estimation of the caesium-137 source term from the Fukushima Daiichi nuclear power plant using a consistent joint assimilation of air concentration and deposition observations
  
  • Winiarek Victor
  • Bocquet Marc
  • Duhanyan Nora
  • Roustan Yelva
  • Saunier Olivier
  • Mathieu Anne
  Atmospheric Environment, Elsevier, 2014, 82, pp.268-279. Inverse modelling techniques can be used to estimate the amount of radionuclides and the temporal profile of the source term released in the atmosphere during the accident of the Fukushima Daiichi nuclear power plant in March 2011. In Winiarek et al. (2012b), the lower bounds of the caesium-137 and iodine-131 source terms were estimated with such techniques, using activity concentration measurements. The importance of an objective assessment of prior errors (the observation errors and the background errors) was emphasised for a reliable inversion. In such critical context where the meteorological conditions can make the source term partly unobservable and where only a few observations are available, such prior estimation techniques are mandatory, the retrieved source term being very sensitive to this estimation. We propose to extend the use of these techniques to the estimation of prior errors when assimilating observations from several data sets. The aim is to compute an estimate of the caesium-137 source term jointly using all available data about this radionuclide, such as activity concentrations in the air, but also daily fallout measurements and total cumulated fallout measurements. It is crucial to properly and simultaneously estimate the background errors and the prior errors relative to each data set. A proper estimation of prior errors is also a necessary condition to reliably estimate the a posteriori uncertainty of the estimated source term. Using such techniques, we retrieve a total released quantity of caesium-137 in the interval 11.6 − 19.3 PBq with an estimated standard deviation range of 15 − 20% depending on the method and the data sets. The "blind" time intervals of the source term have also been strongly mitigated compared to the first estimations with only activity concentration data. (10.1016/j.atmosenv.2013.10.017)
  DOI : 10.1016/j.atmosenv.2013.10.017
• Road traffic impact on urban water quality: a step towards integrated traffic, air and stormwater modelling
  
  • Fallahshorshani Masoud
  • Bonhomme Céline
  • Petrucci Guido
  • Andre Michel
  • Seigneur Christian
  Environmental Science and Pollution Research, Springer Verlag, 2014. Methods for simulating air pollution due to road traffic and the associated effects on stormwater runoff quality in an urban environment are examined with particular emphasis on the integration of the various simulation models into a consistent modelling chain. To that end, the models for traffic, pollutant emissions, atmospheric dispersion and deposition, and stormwater contamination are reviewed. The present study focuses on the implementation of a modelling chain for an actual urban case study, which is the contamination of water runoff by cadmium (Cd), lead (Pb), and zinc (Zn) in the Grigny urban catchment near Paris, France. First, traffic emissions are calculated with traffic inputs using the COPERT4 methodology. Next, the atmospheric dispersion of pollutants is simulated with the Polyphemus line source model and pollutant deposition fluxes in different subcatchment areas are calculated. Finally, the SWMMwater quantity and quality model is used to estimate the concentrations of pollutants in stormwater runoff. The simulation results are compared to mass flow rates and concentrations of Cd, Pb and Zn measured at the catchment outlet. The contribution of local traffic to stormwater contamination is estimated to be significant for Pb and, to a lesser extent, for Zn and Cd; however, Pb is most likely overestimated due to outdated emissions factors. The results demonstrate the importance of treating distributed traffic emissions from major roadways explicitly since the impact of these sources on concentrations in the catchment outlet is underestimated when those traffic (10.1007/s11356-013-2370-x)
  DOI : 10.1007/s11356-013-2370-x
• 3D Radiative and Convective Modeling of Urban Environment: An Example for the City Center of Toulouse
  
  • Qu Yongfeng
  • Milliez Maya
  • Musson-Genon Luc
  • Carissimo Bertrand
  Air Pollution Modeling and its Application XXII, 2014, pp.727-731. (10.1007/978-94-007-5577-2_123)
  DOI : 10.1007/978-94-007-5577-2_123
• An experiment to measure raindrop collection efficiencies: Influence of rear capture
  
  • Quérel Arnaud
  • Lemaitre P.
  • Monier Marie
  • Porcheron E.
  • Flossmann Andrea
  • Hervo Maxime
  Atmospheric Measurement Techniques, European Geosciences Union, 2014, 7 (5), pp.1321-1330. In the case of severe accident with loss of containment in a nuclear plant, radionuclides are released into the atmosphere in the form of both gases and aerosol particles (Baklanov and Sørensen, 2001). The analysis of radioactive aerosol scavenged by rain after the Chernobyl accident highlights certain differences between the modelling studies and the environmental measurements. Part of these discrepancies can probably be attributed to uncertainties in the efficiencies used to calculate aerosol particle collection by raindrops, particularly drops with a diameter larger than one millimetre. In order to address the issue of these uncertainties, an experimental study was performed to close the gaps still existing for this key microphysical parameter. In this paper, attention is first focused on the efficiency with which aerosol particles in the accumulation mode are collected by raindrops with a diameter of 2 mm. The collection efficiencies measured for aerosol particle in the sub-micron range are quantitatively consistent with previous theoretical model developed by Beard (1974) and thus highlight the major role of rear capture in the submicron range. © Author(s) 2014. (10.5194/amt-7-1321-2014)
  DOI : 10.5194/amt-7-1321-2014
• Numerical modelling of aeolian erosion over a surface with non-uniformly distributed roughness elements
  
  • Furieri B.
  • Harion J. L.
  • Milliez M.
  • Russeil S.
  • Santos J. M.
  Earth Surface Processes and Landforms, Wiley, 2014, 39 (2), pp.156-166. The present study is focused on the analysis of the mean wall friction velocity on a surface including roughness elements exposed to a turbulent boundary layer. These roughness elements represent non-erodible particles over an erodible surface of an agglomeration of granular material on industrial sites. A first study has proposed a formulation that describes the evolution of the friction velocity as a function of geometrical parameters and cover rate with different uniform roughness distributions. The present simulations deal with non-uniform distributions of particles with a random sampling of diameters, heights, positions and arrangements. The evolution (relative to geometrical parameters of the roughness elements) of the friction velocity for several non-uniform distributions of roughness elements was analysed by the equation proposed in the literature and compared to the results obtained with the numerical simulations. This comparison showed very good agreement. Thus, the formulation developed for uniform particles was found also to be valid for a larger spectrum of particles noted on industrial sites. The present work aims also to investigate in detail the fluid mechanics over several roughness particles. © 2013 John Wiley & Sons, Ltd. (10.1002/esp.3435)
  DOI : 10.1002/esp.3435
• Fukushima : de la radioactivité dans l'air
  
  • Winiarek Victor
  • Bocquet Marc
  , 2014.
• Source apportionment of PM10 in a north-western Europe regional urban background site (Lens, France) using positive matrix factorization and including primary biogenic emissions
  
  • Waked A.
  • Favez O.
  • Alleman L. Y.
  • Piot C.
  • Petit J.-E.
  • Delaunay T.
  • Verlinden E.
  • Golly B.
  • Besombes Jean-Luc
  • Jaffrezo J.-L.
  Atmospheric Chemistry and Physics, European Geosciences Union, 2014, 14 (7), pp.3325-3346. In this work, the source of ambient particulate matter (PM 10) collected over a one-year period at an urban background site in Lens (France) was determined and investigated using a positive matrix factorization receptor model (US EPA PMF v3.0). In addition, a potential source contribution function (PSCF) was performed by means of the Hybrid Single-Particle Lagrangian Integrated Trajectory (Hys-plit) v4.9 model to assess prevailing geographical origins of the identified sources. A selective iteration process was followed for the qualification of the more robust and meaningful PMF solution. Components measured and used in the PMF included inorganic and organic species: soluble ionic species, trace elements, elemental carbon (EC), sugar alcohols , sugar anhydride, and organic carbon (OC). The mean PM 10 concentration measured from March 2011 to March 2012 was about 21 µg m −3 with typically OM, nitrate and sulfate contributing to most of the mass and accounting respectively for 5.8, 4.5 and 2.3 µg m −3 on a yearly basis. Accordingly, PMF outputs showed that the main emission sources were (in decreasing order of contribution) secondary inorganic aerosols (28 % of the total PM 10 mass), aged marine emissions (19 %), with probably predominant contribution of shipping activities, biomass burning (13 %), mineral dust (13 %), primary biogenic emissions (9 %), fresh sea salts (8 %), primary traffic emissions (6 %) and heavy oil combustion (4 %). Significant temporal variations were observed for most of the identified sources. In particular, biomass burning emissions were negligible in summer but responsible for about 25 % of total PM 10 and 50 % of total OC in winter-time. Conversely, primary biogenic emissions were found to be negligible in winter but to represent about 20 % of total PM 10 and 40 % of total OC in summer. The latter result calls for more investigations of primary biogenic aerosols using source apportionment studies, which quite usually disregard this type of source. This study further underlines the major influence of secondary processes during daily threshold exceedances. Finally, apparent discrepancies that could be generally observed between filter-based studies (such as the present one) and aerosol mass spectrometer-based PMF analyses (organic fractions) are also discussed. (10.5194/acp-14-3325-2014)
  DOI : 10.5194/acp-14-3325-2014