PARAMETERIZATION OF BELOW-CLOUD SCAVENGING OF HIGHLY SOLUBLE GASES UNDER CONVECTIVE CONDITIONS

A model is developed to compute below-cloud scavenging coefficients du ring rain of irreversibly soluble gases under convective circumstances . The model takes evaporation of raindrops into account. All results a re parameterized as functions of the temperature, relative humidity, r ainfall rate at ground level. and diffusivities of the gases at 25 deg rees C. Functions are also found for the cloud base height, the smalle st drop that can reach the ground and the amount of rain evaporated be tween the cloud base and the ground. The results are presented in such a way that they can easily be used in atmospheric transport models. E xamples are given for NH3, HCl, H2O3, HNO3 and N2O5.