| Abstract: In an El Nino event, positive SST anomalies usually
appear in remote ocean basins such as the South China Sea, the Indian Ocean,
and the tropical North Atlantic approximately 3 to 6 months after SST anomalies
peak in the tropical Pacific. Ship data from 1952 to 1992 and satellite
data from the 1980s both demonstrate that changes in atmospheric circulation
accompanying El Nino induce changes in cloud cover and evaporation which,
in turn, increase the net heat flux entering these remote oceans. It is
postulated that this increased heat flux is responsible for the surface
warming of these oceans. Specifically, over the eastern Indian Ocean and
South China Sea, enhanced subsidence during El Nino reduces cloud cover
and increases the solar radiation absorbed by the ocean, thereby leading
to enhanced SSTs. In the tropical North Atlantic, a weakening of the trade
winds during El Nino reduces surface evaporation and increases SSTs. These
relationships fit the concept of an "atmospheric bridge" that
connects SST anomalies in the central equatorial Pacific to those in remote
tropical oceans. |