Simulation of Aerosol Indirect Effects on Wintertime Stratocumulus Clouds over Northwestern Pacific

Aerosol effects on the roll-type stratocumulus clouds over the Northwestern Pacific were simulated using a double-moment aerosol-interactive microphysical scheme coupled into the Weather Research and Forecast (WRF) model. Microphysical and macrophysical responses of such stratocumulus clouds were examined under a wide range of aerosol concentrations. The results clearly show the so-called Twomey effect but defied some of the Albrecht effects. The defiance includes a decrease in cloud thickness and cloud cover with increasing aerosol concentration, which partially offset the Twomey effect by up to 20% in cloud albedo. Such reversed Albrecht effects stem mainly from the dynamic response to changes in atmospheric stability that associated with drizzle formation and evaporation in the sub-cloud layer.