The coupled effect of mid-tropospheric moisture and aerosol abundance on deep convective clouds dynamics and microphysics

Several recent studies have found that convection in a dry atmosphere tends to be more readily diminished by entrainment of very dry air. The process of suppression of deep convection by dry layers touches on the fundamental issues in representing moist convection because mixing plays an important role in convection. An important process that has not been considered is the effect that aerosol properties have on the response of clouds to dry layers. This presentation seeks to investigate the coupled effect of mid-tropospheric moisture and aerosol abundance on a deep convective cloud. Our specific objective is to study the response of a convective cloud to dryness in the mid troposphere with different initial aerosol loadings. We investigate the issue with a dynamic cloud model with bin-resolved microphysics and aqueous-phase chemistry. We found that the impact of dryness in the mid troposphere varies greatly with initial aerosol abundance. When the aerosol abundance is high, the impact of the dry layers is sufficiently large as to alter cloud dynamics, cloud top height and microphysics, while the effects are much weaker under low aerosol conditions. The research contributes to and extends our current understanding of factors influencing deep convective clouds. The explicit microphysics simulations also provide information on the level of model complexity required to study such interactions. The responses we describe depend on changes in drop spectra, which cannot be achieved by a mesoscale model with parameterized microphysics or a cloud resolving model with bulk microphysics.