An aerosol-dipole event over the tropical Indian Ocean during 2006

Using aerosol optical depth (AOD at 550 nm) from the moderate-resolution imaging spectroradiometer, surface winds, outgoing long-wave radiation from National Centers for Environmental Prediction/National Center for Atmospheric Research reanalysis, and rainfall from Tropical Rainfall Measuring Mission data sets, we report a dipolelike variability in the aerosol concentration over the region (40° E-130° E; 10° S-10° N) during September, October, and November 2006. Positive AOD anomalies (+0.4 to +0.6) (relative to the 2000-2008 climatological average) along the equatorial East Indian Ocean and Indonesia and negative AOD anomalies (-0.2 to -0.4) over the western, northwestern, and central Indian Ocean characterize an aerosol-dipolelike variability. This eastwest variability of the aerosol loading along the Indian Ocean is linked to the anomalously weak easterlies associated with the 2006 Indian Ocean Dipole event. The weaker easterlies lead to the hovering of the aerosol plume over Indonesia/Sumatra coast (98°E), enhancing the positive anomalies of AODs, while excessive rainfall over the central Arabian Sea caused the negative AOD anomalies