Role of wind shear at different levels in aerosol effects on deep convective clouds

Description

Aerosols could invigorate or suppress convection by serving as cloud condensation nuclei (CCN). Our previous studies indicated that vertical wind shear plays a key role in determining whether aerosols enhance or suppress convective intensity. That is, aerosols generally enhance convection under weak wind shear conditions for warm-based deep convective clouds; increasing wind shear dampens the aerosol invigoration effect and even leads to a suppression effect. However, the vertical wind shear at the different levels should have a very different impact on cloud dynamics, which could lead to significantly different aerosol effects on convection. In this study, we conduct the sensitivity study by changing the wind shear intensity at the lower level (0–5 km), the middle level (5–10 km), and the upper level (above 10 km) using the Weather Research and Forecasting (WRF) model with spectral-bin microphysics (SBM) to look into how aerosol impact on deep convective clouds changes with the different levels of wind shear and which level of wind shear plays a more significant role in terms of aerosol effects on cloud dynamics, macrophysical and microphysical properties, and radiative forcing. We find that CCN effects are the most significant under larger low-level or middle-level wind shear conditions. When wind shear is very high in the upper levels, CCN effects are much reduced.