Importance of the surface size distribution of erodible material: an improvement on the Dust Entrainment And Deposition (DEAD) Model

摘要

This paper is based on dust aerosol cycle modelling in the atmospheric modelALADIN (Aire Limitée Adaptation dynamique DéveloppementInterNational) coupled with the EXternalised SURFace scheme SURFEX. Its maingoal is to create an appropriate mineral dust emission parameterizationcompatible with the global database of land surface parameters ECOCLIMAP,and the Food and Agriculture Organization (FAO) soil type database inSURFEX. An improvement on the Dust Entrainment And Deposition scheme (DEAD)is proposed in this paper by introducing the geographical variation ofsurface soil size distribution, the Marticorena and Bergametti (1995)formulation of horizontal saltation flux and the Shao et al. (1996)formulation of sandblasting efficiency α. To show the importance of themodifications introduced in the DEAD, both sensitivity and comparativestudies are conducted in 0 dimensions (0-D) and then in 3 dimensions (3-D)between the old DEAD and the new DEAD. The results of the 0-D simulationsindicate that the revised DEAD scheme represents the dust source emissionbetter, particularly in the Bodélé depression, and provides areasonable friction threshold velocity. In 3-D simulations, smalldifferences are found between the DEAD and the revised DEAD for thesimulated Aerosol Optical Depth (AOD) compared with the AErosol ROboticNETwork (AERONET) photometer measurements available in the African MonsoonMultidisciplinary Analyses (AMMA) databases. For the surface concentration,a remarkable improvement is noted for the revised DEAD scheme.