Light\nPrecipitation\nrather than Total Precipitation\nDetermines Aerosol Wet Removal

Precipitation scavenging is an important\nsink for both\norganic\nand inorganic pollutants in the atmosphere. However, there has been\ncontroversy over the relative importance of different precipitation\ncharacteristics (i.e., the precipitation amount, intensity, frequency,\nand duration) in the removal of air pollutants. It is critical to\nreach a consensus on which precipitation characteristics are most\nsignificant for aerosol wet removal. In this study, the analysis of\nmultisource in situ observations of aerosol wet deposition worldwide\nindicates that the precipitation frequency plays a first-order role\nin scavenging aerosols. This is because large amounts of air pollutants\nare efficiently removed at precipitation initiation. As the duration\nand amount of precipitation increase, the scavenging efficiency decreases\nsharply. Consequently, it is featured that light precipitation, due\nto its high frequency of occurrence, rather than total precipitation,\ndetermines climatological aerosol wet deposition. To further confirm\nthis, a state-of-the-art global climate model with convection resolved\nis modified to reduce the light precipitation frequency in both stratiform\nand convective cloud regimes. Results show widespread increases in\naerosol optical depth (AOD) due to the reduced wet deposition. The\nspatial distribution of aerosol wet deposition changes resembles that\nof changes in the light precipitation frequency rather than that of\ntotal precipitation changes. These findings are consistent with those\nfrom the Coupled Model Intercomparison Project Phase 6 multimodel\nsimulations, which show that the intermodel uncertainty in simulated\nAOD correlates more strongly with the uncertainty in light precipitation\nfrequency than with that in total precipitation.