Effect of Rain Scavenging on Altitudinal Distribution of Soluble Gaseous Pollutants in the Atmosphere

摘要

We suggest a model of rain scavenging of soluble gaseous pollutants in theatmosphere. It is shown that below-cloud gas scavenging is determined bynon-stationary convective diffusion equation with the effective Peclet number.The obtained equation was analyzed numerically in the case of log-normaldroplet size distribution. Calculations of scavenging coefficient and the ratesof precipitation scavenging are performed for wet removal of ammonia (NH3) andsulfur dioxide (SO2) from the atmosphere. It is shown that scavengingcoefficient is non-stationary and height-dependent. It is found also that thescavenging coefficient strongly depends on initial concentration distributionof soluble gaseous pollutants in the atmosphere. It is shown that in the caseof linear distribution of the initial concentration of gaseous pollutantswhereby the initial concentration of gaseous pollutants decreases withaltitude, the scavenging coefficient increases with height in the beginning ofrainfall. At the later stage of the rain scavenging coefficient decreases withheight in the upper below-cloud layers of the atmosphere.