PNNL

Abstract

The effects of entrained environment air and aerosols on cloud properties remain a critical 16 yet understudied topic. This study first introduces a new entraining cloud parcel model 17 considering entrained aerosols. With entrained aerosols represented by a newly introduced 18 parameter, the impacts of entrainment rate and entrained aerosols on cloud microphysical 19 properties are investigated. The results show that the relationships between entrainment rate 20 and cloud microphysical properties are highly nonlinear when the entrained aerosols vary. With 21 the lateral entrainment-mixing, a new phenomenon is revealed that the height of maximum 22 parcel supersaturation cannot be reached when the entrainment rate is beyond a certain 23 critical value. This new critical entrainment rate is different from the critical entrainment rate 24 defined by Barahona and Nenes [2007], beyond which clouds cannot form. This finding has 25 important implications for developing parameterization of droplet activation, which is based 26 primarily on the assumption of the existence of maximum supersaturation.