Aerosol affects cloud development through radiative effect and microphysical effect. For deep convective clouds, the two processes have opposite effects on cloud development. Aerosols reduces the solar energy to the surface, rendering less energy for cloud development. Aerosols can invigorate convective clouds by suppressing droplet growth at low level and release latent heat above freezing level. This study attempts to identify and evaluate the two competing effects using long term observational data in ARM SGP site. Various factors that may affect the two effects will be investigated, including cloud parameters, aerosol properties, and meteorological variables such as relative humidity (RH), surface fluxes and wind shear.