Grandey, B. S., A. Gururaj, P. Stier and T. M. Wagner (2014), Rainfall-aerosol relationships explained by wet scavenging and humidity, Geophysical Research Letters, doi:10.1002/2014GL060958
Negative rainfall-aerosol relationships arise due to wet scavenging (removal of aerosol by rainfall).
Satellites poorly sample aerosol populations depleted by wet scavenging.
Positive rainfall-aerosol relationships arise due to humidification effects. Increased relative humidity causes many aerosols to swell, and high relative humidity is required for rainfall to occur.
Maps of the differences in precipitation rate between clean and polluted conditions during June-July-August. (a) Difference in total precipitation rate between clean (total aerosol optical depth < 33rd percentile) and polluted (total aerosol optical depth > 67th percentile) conditions for the ECHAM5-HAM control simulation. (b) Similar to (a) but for convective precipitation rate instead of total precipitation rate. (c) Similar to (b) but for the NoConvScav simulation, in which scavenging of aerosols by convective precipitation has been turned off. (d) Similar to (c) but for dry aerosol optical depth instead of total aerosol optical depth. The annotated arrows show the conceptual steps linking each figure. Area-weighted means are provided at the side of each figure.