Middle-East deserts help alleviate droughts over South Asia: Study

The big dust storms of Middle-Eastern deserts transported to the Arabian Sea might improve rainfall over South Asia, particularly throughout extreme drought episodes over India.

According to a study by researchers at the IIT Bhubaneswar, deserts are the Middle-Eastern regions that receive the least amount of rainfall among all biomes, however, they are known to modulate global and regional climate through various pathways.

The study has been published recently in the Nature Publishing Group journal Climate and Atmospheric Science.

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The first indication of this was provided by a study published in the journal Nature Geoscience in 2014 by the same team and collaborators abroad.

That study showed that desert dust aerosols emitted from the Middle-Eastern/Arabian and North African deserts increase rainfall over India at short time scales of about a week or two.

This is made possible due to the warming induced by this dust over the Arabian Sea, which acts as a source of energy to speed up the monsoon circulation (winds, moisture) towards the Indian region. This relationship is now stronger during drought years associated with El-Nino. They also indicate that this dust induced rainfall enhancement is widespread across the whole south Asian monsoon domain, often occurring as a pulse that triggers short term increased rainfall in an otherwise dry situation.

“India has faced droughts or large-scale deficits and changes in the spatial pattern of monsoon rainfall due to ongoing climate change. However, with global warming in place and changing wind patterns, we can expect a rise in dust storms across Middle-Eastern deserts in the coming years. This dust may get transported to the Arabian Sea under favourable conditions and trigger short heavy rain spells over the Indian region. In other words, nature compensates for the deficit created by human activities,” said V Vinoj, Assistant Professor, School of Earth Ocean and Climate Sciences, IIT Bhubaneswar.

In a press statement circulated through Climate Trends, he said: “It is well established that anthropogenic factors reduce rainfall and continue to do so for long-timescale (decades). Still, the silver lining is that there is a short period of respite to this drying trend in the form of increased short-time (about a week or so) rainfall. With the increasing potential of El-Nino like conditions in the future, these dust induced effects will become increasingly important in understanding changing characteristics of rainfall over India.”

Dr Vinoj said that recent studies have shown a decline in the desert dust over India due to increased pre-monsoon rains over the North-Western parts of India, potentially due to regional effects of climate change.

“However, human activities with associated emissions will continue to rise due to the country's economic development. In addition, increased dust over the middle eastern deserts transported over the Arabian Sea increases short period rainfall over India. So, on the one hand, dust emitted over India is declining, whereas dust over the Arabian Sea is rising to lead to increased rainfall. It will be interesting to see how these changes combinedly impact air quality and rainfall,” he added.

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