Contrasting roles of clouds as a sink and source of aerosols: A quantitative assessment using WRF-Chem over East Asia

Clouds play two contrasting roles in the fate of aerosols as a sink through wet scavenging and source medium for aqueous-phase secondary aerosol formation. The contributions clouds to near-surface particulate matter with diameter less than 2.5 μm (PM2.5) are quantitatively examined particular focus on boundary-layer using Weather Research Forecasting model coupled chemistry (WRF-Chem). Overall, net contribution daily-mean PM2.5 is much larger (−5 μg m−3 −22 m−3) that cloud (∼0.9 m−3). effects found over large spatial extent even no-rainy regions last long time (∼2 days). amount scavenged by rainfall varies greatly, but it increases liquid water path (LWP) general sense. So, mostly removed when have LWPs. For thin LWPs 30–80 g m−2, reduction due barely sensitive LWP role becomes non-negligible. A relatively increase sulfate mass base height (CBH) lower ∼1.2 km clouds, occurrence fraction which plays dominant up ∼30% CBH lower. These results highlight fog and/or non-precipitating stratus likely substantial formation aerosols. case study reveals presence can contribute increasing at maximum rate 1.5 h−1.