HR: 0800h
AN: A31C-0074    [Abstracts]
TI: Optimization of the particle size bin scheme in modeling dry deposition of dust
AU: * Foret, G
EM: foret@lisa.univ-paris12.fr
AF: LISA CNRS-Universite Paris 7/Paris 12, CMC 61 avenue du General de Gaulle, Creteil, 94010 France
AU: Bergametti, G
EM: bergametti@lisa.univ-paris12.fr
AF: LISA CNRS-Universite Paris 7/Paris 12, CMC 61 avenue du General de Gaulle, Creteil, 94010 France
AU: Dulac, F
EM: dulac@lisa.univ-paris12.fr
AF: LISA CNRS-Universite Paris 7/Paris 12, CMC 61 avenue du General de Gaulle, Creteil, 94010 France
AU: Dulac, F
EM: dulac@lisa.univ-paris12.fr
AF: LSCE CEA-CNRS, CEA Saclay 709, Gif-sur-Yvette, 91191 France
AB: Mineral dust is a major component of the tropospheric aerosol and Aeolian erosion is responsible for long-range transfer of large amounts of particles which impact the biogeochemical cycles, the radiative budget and atmospheric chemistry. Dry deposition is a major pathway for the removal of dust particles from the atmosphere, and their lifetime is particularly sensitive to dry deposition due to a size distribution covering the large particle size range. Thus, precise dry deposition schemes are required into dust transport models for a correct assessment of the dust dry deposition fluxes and mass transfers from source regions. Because the dust particle size distribution ranges over several decades and because the dry deposition velocity versus particle size is strongly non-linear, such accuracy needs a large number of size bins in the models, not always compatible with reasonable computation times. In this paper, we present a new approach to optimize the number of size bins for the dry deposition scheme into dust transport models. We develop a method in which the size range covered by each size bin is defined according to the gradient in dry deposition velocity relative to the particle size. Using a 1000-bins simulation as a reference case, we compare the dry deposition fluxes in mass and number computed with our gradient method and with the classical method based on iso-logarithmical bins, for various numbers of size bins. The results show that the new approach leads to improvements in terms of accuracy and time computation for an identical number of bins. We further determine the minimal number of bins to get a given accuracy of the dry deposition flux. For the mass size distribution of dust particles we have used, results indicate that an accuracy of 5% in the dust particle dry deposition flux can be obtained by using only 5 bins where the classical method gives accuracy not better than 40%.
DE: 4801 Aerosols (0305)
DE: 0305 Aerosols and particles (0345, 4801)
DE: 0322 Constituent sources and sinks
DE: 0368 Troposphere--constituent transport and chemistry
SC: Atmospheric Sciences [A]
MN: 2004 AGU Fall Meeting