Washington: Raising air pollution over the Indian sub-continent could be partly blamed for a recent increase in the intensity of tropical cyclones in the Arabian Sea, according to a new multi-institutional study.
Traditionally, prevailing wind-shear patterns prevent cyclones in the Arabian Sea from becoming major storms.
The study, however, suggested the weakening of the winds aloft has enabled the formation of stronger cyclones in recent years – including storms in 2007 and 2010 that were the first recorded storms ever to enter the Gulf of Oman.
“There has been a real uptick in the intensity of tropical cyclones in the Arabian Sea. We wanted to understand why, and we think we found the reason,” said the study’s lead author, Amato Evan, an environmental scientist in the University of Virginia``s College of Arts and Sciences.
The weakening wind patterns over the past 30 years have corresponded with a build-up of aerosols in the atmosphere over India, which deflect sunlight from the surface, creating dimming at ground level, the researchers said.
The aerosol build-up creates formations known as “atmospheric brown clouds,” in which smog from diesel emissions, soot and other by-products of biomass burning accumulates and becomes widespread to a degree significant enough to be a climatic force.
The 1.9-mile-thick brown cloud has been linked to altered rainfall patterns in South Asia.
Veerabhadran Ramanathan, a study co-author, Evan and his colleagues hypothesize that the brown cloud over India disrupts normal air circulation and inhibits summertime warming of the surface, causing sea surface temperatures in the northern Arabian Sea to more closely match cooler temperatures closer to the equator.
The study appeared in the Nov. 3 issue of the journal Nature.