Publications

2003

• Rebuilding sources of linear tracers after atmospheric concentration measurements
  
  • Issartel J.-P.
  Atmospheric Chemistry and Physics, European Geosciences Union, 2003, 3 (6), pp.2125. The identification of widespread sources of passive tracers out of atmospheric concentration measurements has become an important challenge of modern meteorology. The paper proposes some mathematical tracks to address the reconstruction of the complex space-time geometry of the sources of linear tracers. The methods are based upon the use of retroplumes. The inverse problem is addressed in a deterministic non statistical frame. The information obtained by local measurements is spread by introducing the concept of illumination. The constraint that the source is non negative is also addressed. The experimental source ETEX1 is rebuilt in order to evaluate an impulse response of the algorithms.
• Data assimilation and inverse modeling of atmospheric chemistry
  
  • Sportisse Bruno
  • Quélo Denis
  Proceedings of the National Academy of Sciences, India Section A: Physical Sciences, Springer, 2003, 69. No abstract
• Reduction of multiphase atmospheric chemistry
  
  • Djouad Rafik
  • Sportisse Bruno
  • Audiffren Nicole
  Journal of Atmospheric Chemistry, Springer Verlag, 2003, 46 (2), pp.131-157. The aim of this article is to investigate the dynamical behaviour of multiphase atmospheric chemical mechanisms. Reducing procedures are applied to a multiphase chemical box model including gas-phase reactions, aqueous-phase reactions and interfacial mass transfer. The lumping of species is computed in an automatic way using an efficient algorithm (APLA). The computed lumped species are related to the fast behaviour of chemical and microphysical processes such as Chapman cycle, ionic dissociations within the cloud drops and interfacial Henry's equilibria. Depending on some parameters (liquid water content, droplet radius) mixed lumped species (including both phases) may also be computed. We show the existence of hierarchical reduced models due to the existence of multiple timescales. We use a special algorithm (DAN2) in order to solve the reduced models. Such models are accurate and the relative error remains under the threshold of 1%. The speed-up is up to a factor 5 compared with a fully implicit method (Gear) for the same accuracy. The key point is that it provides a good qualitative understanding for the behaviour of the kinetic scheme (10.1023/A:1026067610565)
  DOI : 10.1023/A:1026067610565
• A sensitivity analysis study for RADM2 mechanism using automatic differentiation
  
  • Djouad Rafik
  • Audiffren Nicole
  • Sportisse Bruno
  Atmospheric Environment, Elsevier, 2003, 37 (22), pp.3029-3038. A sensitivity analysis of an atmospheric multiphase mechanism is performed using an automatic differentiation tool. The sensitivity of some key concentrations is computed with respect to some input parameters (kinetic rates, microphysical parameters). The package odyssee is used in order to obtain the so-called linear tangent model giving the derivatives of outputs with respect to inputs. The direct model takes into account gas-phase reactions, aqueous-phase reactions and interfacial mass transfer and is based on the radm2 mechanism. Local sensitivity coefficients are computed for two different scenarii, rural and sub-urban. We focus in this study on the sensitivity of the gas-phase O3–NOx–HOx system with respect to some aqueous phase reactions and we investigate the influence of the reduction in the photolysis rates in the area below the cloud region. This preliminary work illustrates how powerful automatic differentiation tools may be for the study of large chemical mechanisms. We show for instance that the oxidation of trace metals (FeII, FeIII, Cu+ and Cu2+) in the case of low S(IV) polluted area is not always in disfavor of HOx gaseous concentrations, as it is usually claimed. (10.1016/S1352-2310(03)00322-4)
  DOI : 10.1016/S1352-2310(03)00322-4
• Rebuilding sources of linear tracers after atmospheric concentration concentration
  
  • Issartel J.-P.
  Atmospheric Chemistry and Physics Discussions, European Geosciences Union, 2003, 3 (3), pp.3171-3203. The identification of widespread sources of passive tracers out of atmospheric concentration measurements has become an important challenge of modern meteorology. The paper proposes some mathematical tracks to address this reconstruction of the complex space-time geometry of the sources. The methods are based upon the use of retroplumes. The inverse problem is addressed in a deterministic non statistical frame. The information obtained by local measurements is spread by introducing the concept of illumination. The constraint that the source to be rebuilt is non negative is also addressed. The experimental source ETEX1 is rebuilt in order to evaluate an impulse response of the algorithms.
• Inverse transport for the verification of the Comprehensive Nuclear Test Ban Treaty
  
  • Issartel J.-P.
  • Baverel J.
  Atmospheric Chemistry and Physics, European Geosciences Union, 2003, 3 (3), pp.486. An international monitoring system is being built as a verification tool for the Comprehensive Test Ban Treaty. Forty stations will measure on a worldwide daily basis the concentration of radioactive noble gases. The paper introduces, by handling preliminary real data, a new approach of backtracking for the identification of sources of passive tracers after positive measurements. When several measurements are available the ambiguity about possible sources is reduced significantly. The approach is validated against ETEX data. A distinction is made between adjoint and inverse transport shown to be, indeed, different though equivalent ideas. As an interesting side result it is shown that, in the passive tracer dispersion equation, the diffusion stemming from a time symmetric turbulence is necessarily a self-adjoint operator, a result easily verified for the usual gradient closure, but more general.
• Arsenic dispersion over Central Chile assessed through forward and inverse modeling
  
  • Quiroz Henry
  • Gallardo Laura
  • Berroir Jean-Paul
  • Herlin Isabelle
  • Issartel Jean-Pierre
  • Sportisse Bruno
  , 2003, 5. We investigate the atmospheric transport of arsenic (As) emitted from a copper smelter and its potential impact on the air quality of the city of Santiago (33.5ºS, 70.8ºW, 500 m.a.s.l), with 5x106 inhabitants. Santiago is located in a basin in the central part of Chile bounded by the high Andes (4500 m altitude on average) to the east, a lower parallel mountain range to the west (1500 m altitude on average), and two east-to-west mountain chains to the north and south of the basin respectively. Anthropogenic arsenic is emitted to the atmosphere in connection with the smelting of metals such as gold and copper, coal combustion and herbicide use. The main single As source in Central Chile is Caletones (34º05'S, 70º27'W, 2400 m.a.s.l.) located some 150 km south of Santiago, with an emission rate of 1200 ton As/yr in 2000. There is some evidence that the influence of Caletones on the air quality of the Santiago basin increases in connection with intensive coastal lows (CLs), which are synoptic disturbances that bring down the subsidence inversion. However, the scarcity of observations representative of the regional-scale transport patterns, the complex topography of the area where Caletones is located and over which dispersion occurs, the extreme stability reached during CLs make it necessary to better assess the transport processes potentially responsible for these impacts. Here we assess this by means of inverse and forward modeling.
• Solving reduced chemical models in Air Pollution Modelling
  
  • Djouad Rafik
  • Sportisse Bruno
  Applied Numerical Mathematics: an IMACS journal, Elsevier, 2003, 44 (1-2), pp.49-61. This article follows [R. Djouad, B. Sportisse, Appl. Numer. Math. 43 (2002) 383] in which we have proposed an automatic method in order to generate reduced atmospheric chemical mechanisms. On the basis of the slow/fast behaviour of chemical kinetics the exact model is replaced by a differential-algebraic system. We propose here an easy to perform algorithm in order to integrate such systems with a low CPU cost. Comparison is made with some classical solvers such as Euler Backward Implicit (EBI), QSSA and the second-order Rosenbrock method ROS2. This proves the efficiency and the accuracy of the proposed algorithm. We also show that the classical QSSA-like methods cannot be used apart from the framework of reduction procedures, which explains their rather poor accuracy. (10.1016/S0168-9274(02)00142-3)
  DOI : 10.1016/S0168-9274(02)00142-3
• Mathematical investigation of mass transfer for atmospheric pollutants into a fixed droplet with aqueous chemistry
  
  • Sportisse Bruno
  • Djouad Rafik
  Journal of Geophysical Research: Atmospheres, American Geophysical Union, 2003, 108 (D2), pp.4073. The objective of this article is to investigate some of the classical parameterizations used for modeling mass transfer between interstitial gas and cloud droplets for aqueous-phase models in Air Pollution Modeling [ Schwartz, 1986 ]. After an appropriate scaling of the initial model (a set of two coupled Partial Differential Equations), we apply the singular perturbation theory and some theoretical results of Reaction-Diffusion models with large diffusion coefficients. This justifies the use of classical parameterizations in a large range of parameters. Moreover, we propose a new parameterization of mass transfer, taking into account aqueous-phase diffusion limitations. This parameterization is based on a double-film model and may have an impact for some species, as it is illustrated with a simple box model (10.1029/2001JD001336)
  DOI : 10.1029/2001JD001336
• A stochastic approach for the numerical simulation of the general dynamics equation for aerosols
  
  • Debry Edouard
  • Sportisse Bruno
  • Jourdain Benjamin
  Journal of Computational Physics, Elsevier, 2003, 184 (2), pp.649-689. We present in this article a stochastic algorithm based mainly on [Monte Carlo Methods and Applications 5(1) (1999) 1; Stochastic particle approximations for Smoluchowski's coagulation equation. Technical Report, Weierstrass-Institut for Applied Analysis and Stochastics, 2000. Preprint No. 585] applied to the integration of the General Dynamics Equation (GDE) for aerosols. This algorithm is validated by comparison with analytical solutions of the coagulation-condensation model and may provide an accurate reference solution in cases for which no analytical solution is available. (10.1016/S0021-9991(02)00041-4)
  DOI : 10.1016/S0021-9991(02)00041-4