Impact of Saharan Dust on Tropical North Atlantic SST

Abstract

A combination of satellite and in situ datasets is used to investigate the impact of interannual changes in atmospheric dust content on the sea surface temperature (SST) of the tropical North Atlantic Ocean. Throughout most of the region the authors find, in agreement with previous studies, that positive anomalies of dust are associated with a significant reduction in surface shortwave radiation (SWR), while negative anomalies of dust are associated with an enhancement of SWR. Statistical analysis for 1984?2000 suggests that changes in dustiness in the tropical North Atlantic (10°?25°N, 20°?60°W) explained approximately 35% of the observed interannual SST variability during boreal summer, when climatological dust concentrations are highest. Measurements from a long-term moored buoy in the central tropical North Atlantic are used to investigate the causes of anomalously cool SST that occurred in conjunction with a period of enhanced dustiness at the start of the unexpectedly quiet 2006 hurricane season. It is found that surface SWR varied out of phase with dustiness, consistent with historical analyses. However, most of the anomalous cooling occurred prior to the period of enhanced dustiness and was driven primarily by wind-induced latent heat loss, with horizontal oceanic heat advection and SWR playing secondary roles. These results indicate that dust-induced changes in SWR did not play a major direct role in the cooling that led up to the 2006 Atlantic hurricane season.