Results of field experiments of aerosol scavenging by precipitation are considered. Scavenging factor was evaluated for aerosol particles within the range greater 0.3 mkm. Experiments have clearly shown that one can calculate scavenging factor only thoroughly analyzing results of each measurement because there are lot of factors (aerosol concentration variations due to synoptical processes, daily aerosol concentration trend, wind, local aerosol sorcerers, etc) that seriously complicate processing procedure. Nonstationary parameterized model of Cu cloud have been used also to calculate scavenging factor.