Ocean Temperatures Affect Intensity of the South Asian Monsoon and Rainfall

Warmer or colder sea surface temperatures (SST) may affect one of the world's key large-scale atmospheric circulations that regulate the intensity and breaking of rainfall associated with the South Asian and Australian monsoons, according to new research from NASA.

A monsoon is a wind that changes direction with the seasons. Monsoons develop from changing patterns of atmospheric circulation, which are caused by changes in heating and cooling of land and oceans. One of the strongest and most well-known monsoons is the one which affects India and Southeast Asia in June through September.

The summer monsoon blows southwesterly across the Indian Ocean and is extremely wet. During the summer monsoon, particularly in July, there is usually a break period in the monsoon, when the rains stop and re-start. A phenomenon known as the Madden Julian Oscillation (MJO) has been found to affect that break and the variation of the MJO is affected by the variation of the SSTs.

Man Li Wu, a researcher from Goddard and lead author of the study, used computer models that simulate the atmosphere in the region. One of the purposes of this study is to examine to what extent intra-seasonal SST variations affect the MJO.

Siegfried Schubert, a co-author on the paper from Goddard said that, "the MJO plays an important role in the variability of the South Asian monsoons. Changes in SST may be responsible for between 15% and 30% of the fluctuations that occur in the strength of the MJO.

For the full article on the computer model study of the atmospheric circulations, go to: http://www.gsfc.nasa.gov/topstory/20021015monsoon.html