| As the collision theory for raindrop and aerosol particle is important in below-cloud scavenging, collision efficiency as a function of raindrop (Dp) and aerosol diameter (dp) is discussed. The scavenging coefficient (SC) below thundercloud is5to6times higher than those under non-thundercloud while dp less than1μm. Raindrop size distribution and aerosol size distribution under different precipitation type is also discussed. Heavy rain can wash out more aitken and coarse mode aerosol. Compared the exponential relationship between scavenging coefficient and rainfall intensity in various aerosol type. Scavenging coefficient is positively correlated to parameters. Field measurements of aerosol number concentration on bottom and top, with meteorological elements during June to August, in2011, on mountain Huangshan are used to analyze the change characteristics of observed and theoretical SC. The field inspection of raindrop and aerosol size distribution with meteorological elements during June to July, in2013, in Nanjing is used to simulate raindrop size distribution in theoretical scavenging coefficient. It shows that observed scavenging coefficient of ultrafine-sized particle is accord with theoretical values,5to6times higher than theoretical scavenging coefficient in mountain Huangshan. Submicron-sized particle scavenging coefficient is higher than those below non thundercloud. The theoretical scavenging coefficient in mountain Huangshan is higher than those in Nanjing. Based on the observations in mountain Huangshan, exponential relationship between the hour-averaged scavenging coefficient and rainfall intensity is derived, in which the correlation coefficient is0.81. In Nanjing, rainfall intensity about1.3mmh-1can wash out more accumulation mode aerosol. |
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