Dust blown into the Arabian Sea from West Asia and North Africa can drive up rainfall in India, and more so during drought years associated with a dreaded El Nino.

This dust-induced relationship will become increasingly important in understanding the changing characteristics of rainfall here given the increasing potential for El Nino conditions, according to researchers.

Intriguing relationship

A paper to this effect, co-authored by G Nandini, V. Vinoj and S.K. Pandey at the School of Earth Ocean and Climate Sciences, Indian Institute of Technology (IIT) Bhubaneswar, has been published in Climate and Atmospheric Science.

An earlier study by the same team and collaborators abroad in Nature Geoscience had shown that dust aerosols emitted from the deserts and blown into the Arabian Sea, especially during severe droughts, go to increase rainfall over India.

This results from warming (due to which the moisture-holding capacity of air goes up) induced by dust over the Arabian Sea, which, in turn, acts as a source of energy to speed up the monsoon circulation (winds and moisture) towards the Indian region.

Short-term rain pulses

This rainfall enhancement is widespread across the South Asian monsoon domain, often occurring as a pulse that triggers short-term increased rainfall in an otherwise dry situation. The researchers highlighted the need for tracking dust storms to understand their effect on monsoon rainfall and even on air quality, another growing problem for India.

Studies show a decline in the desert dust over India due to increased pre-monsoon rain over the North-West, potentially due to the regional effect of climate change, says co-author V Vinoj, Assistant Professor, School of Earth Ocean and Climate Sciences, at IIT Bhubaneswar.

“On the one hand, dust emitted over India is declining, while that being blown into the Arabian Sea is leading to increased rainfall. It will be interesting to see how these changes combine to impact air quality and rainfall,” Vinoj said.

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