Impact of direct radiative forcing of black carbon aerosols on tropical convective precipitation

The direct radiative forcing of black carbon (BC) aerosols is able to cause a significant change in tropical convective precipitation ranging from the Pacific and Indian Ocean to the Atlantic Ocean. This change occurs often well away from emission centers, demonstrating a ‘‘remote climate impact.’’ The detailed mechanism of this change has been analyzed in this study. In the tropical Pacific region, the pattern of BC caused precipitation change is found to be similar to the pattern of precipitation anomaly corresponding to the El Niñ o/Southern Oscillation (ENSO) activities. The BC forced changes in the atmospheric circulation are represented by a strengthened Hadley cell in the Northern Hemisphere, a weakened one in the Southern Hemisphere, an enhancement of the Indian summer monsoon circulation, and a reduction of the lower level easterly wind in the central and east equatorial Pacific. The latter dynamic effect of BC is specifically similar to that of an El Niñ event.