Modulations of dust aerosols on precipitation: Evidence from a typical heavy sandstorm event

Abstract

Dust aerosols pose significant modulations on precipitation, varying with precipitation intensity. In particular, the microphysical influences of dust aerosols on the clouds and diurnal variations of heavy precipitation exhibit substantial uncertainties. Taking the typical heavy sandstorm event occurring on March 15, 2021 in China as an example, we investigate the distinct modulations of dust aerosols on precipitation by the Weather Research and Forecasting model coupled to Chemistry (WRF-Chem) model and multiple observational and reanalysis data. Note that dust aerosols exert opposite influences on moderate and heavy precipitation. The inhibiting effect of dust aerosols on the intensity of light precipitation was observed as dust aerosols increase atmospheric stability by cooling in the lower layers, warming in the upper layers, reducing CAPE (Convective Available Potential Energy), increasing CIN (Convective Inhibition). Additionally, dust aerosols hinder the transformation of cloud droplets to raindrops, leading to decreased mass of rainwater (Qr) and snow (Qs) in the lower and middle atmosphere. In contrast, dust aerosols delay but intensify heavy rainfalls. During the night of heavy rain, dust aerosols can can warm the lower layers and cool the upper layers, increase CAPE and decrease CIN, thereby enhancing convection, making it easier for small cloud droplets to grow into larger raindrops through collision and coalescence. Simultaneously, small cloud droplets in the mid-levels ascend to higher altitudes where they freeze, transforming into ice particles. This process, coupled with the Bergeron-Findeisen mechanism, enhances the intensity of nighttime. These findings provide novel evidence to improve our understanding of dust aerosols-precipitation interaction.