Precipitation scavenging is an important sink for both organic and inorganic pollutants in the atmosphere. However, there has been controversy over the relative importance of different precipitation characteristics (i.e., precipitation amount, intensity, frequency, and duration) in removing air pollutants. It is critical to reach a consensus on which precipitation characteristics are most significant in aerosol wet removal. In this study, the analysis of multi-source in-situ observations of aerosol wet deposition worldwide indicates that precipitation frequency plays a first-order role in scavenging aerosols. This is because large amounts of air pollutants are efficiently removed at precipitation initiation. As the duration and amount of precipitation increase, the scavenging efficiency decreases sharply. Consequently, it is featured that light precipitation, due to its high frequency of occurrence, rather than total precipitation, determines climatological aerosol wet deposition. To further confirm this, a state-of-the-art global climate model with convection resolved is modified to reduce light precipitation frequency in both stratiform and convective cloud regimes. Results show widespread increases in aerosol optical depth (AOD) due to reduced wet deposition. The spatial distribution of aerosol wet deposition changes resembles that of changes in light precipitation frequency rather than that of total precipitation changes. These findings are consistent with those from the Coupled Model Intercomparison Project Phase 6 multi-model simulations, which show that the inter-model uncertainty in simulated AOD correlates more strongly with the uncertainty in light precipitation frequency than with that in total precipitation.
 

Climate modes,Precipitation,aerosol wet deposition