Development of an Aerosol Dynamics Model for Dry Deposition Process Using the Moment Method

An aerosol dynamics model for dry deposition process is developed based on the moment method. Since it is hard to fully apply the moment method to the widely used dry deposition velocity expressions based on the resistance theory, the dry deposition velocity expression by Raupach et al. (2001) Raupach, M. R., Briggs, P. R., Ahmad, N. and Edge, V. E. 2001. Endosulfan Tansport: II. Modeling airborne Dispersal and Deposition by Spray and Vapor. J. Environ. Qual., 30: 729–740. Crossref], PubMed], Web of Science ®] , Google Scholar] is used. Detailed deposition mechanisms such as Brownian diffusion, gravitational settling, and impaction are considered in the expression. To verify the validity of the derived dynamic equation, aerosol dynamics for the dry deposition process is estimated with the expressions of Raupach et al. (2001) Raupach, M. R., Briggs, P. R., Ahmad, N. and Edge, V. E. 2001. Endosulfan Tansport: II. Modeling airborne Dispersal and Deposition by Spray and Vapor. J. Environ. Qual., 30: 729–740. Crossref], PubMed], Web of Science ®] , Google Scholar], of Wesely (1989) Wesely, M. L. 1989. Parameterizations of Surface Resistance to Gaseous Dry Deposition in Regional-Scale, Numerical Models. Atmos. Environ., 23: 1293–1304. Crossref], Web of Science ®] , Google Scholar] modified for particles (Seinfeld and Pandis 1998 Seinfeld, J. H. and Pandis, S. N. 1998. Atmospheric Chemistry and Physics, 958–996. New York, , USA: Wiley.  Google Scholar]), in CMAQ, and with constant value used in RAINS-ASIA. Those expressions give different dynamics. Generally, the result for this study is between the result of modified Wesely's expression and CMAQ. When using the modified Wesely's expression with the number of sections being equal or smaller than 10, the resultant size distribution does not give the peak shape accurately.