Effects of turbulence on mixed‐phase deep convective clouds under different basic‐state winds and aerosol concentrations

Abstract

AbstractThe effects of turbulence‐induced collision enhancement (TICE) on mixed‐phase deep convective clouds are numerically investigated using a 2‐D cloud model with bin microphysics for uniform and sheared basic‐state wind profiles and different aerosol concentrations. Graupel particles account for the most of the cloud mass in all simulation cases. In the uniform basic‐state wind cases, graupel particles with moderate sizes account for some of the total graupel mass in the cases with TICE, whereas graupel particles with large sizes account for almost all the total graupel mass in the cases without TICE. This is because the growth of ice crystals into small graupel particles is enhanced due to TICE. The changes in the size distributions of graupel particles due to TICE result in a decrease in the mass‐averaged mean terminal velocity of graupel particles. Therefore, the downward flux of graupel mass, and thus the melting of graupel particles, is reduced due to TICE, leading to a decrease in the amount of surface precipitation. Moreover, under the low aerosol concentration, TICE increases the sublimation of ice particles, consequently playing a partial role in reducing the amount of surface precipitation. The effects of TICE are less pronounced in the sheared basic‐state wind cases than in the uniform basic‐state wind cases because the number of ice crystals is much smaller in the sheared basic‐state wind cases than in the uniform basic‐state wind cases. Thus, the size distributions of graupel particles in the cases with and without TICE show little difference.