This story is from September 14, 2018

University of Hyderabad team decodes secrets behind less monsoon rainfall

University of Hyderabad team decodes secrets behind less monsoon rainfall
HYDERABAD: Researchers from the University of Hyderabad (UoH) have found out why the southwest monsoon, the lifeline of Indian agriculture, fails quite regularly bringing in less rainfall. They have noticed that pollution in the form of aerosols is stopping the rain to fall from the clouds.
Aerosols are suspended solid or liquid particles in air, and they have been helping the clouds to grow vertical and cool down, leading to less quantum of rainfall.
The findings of the study were published on Friday in the prestigious science journal, Nature.
Southwest monsoon begins in the first week of June and retreats in the last week of September. Also called the summer monsoon, it is important for the Indian economy, particularly the peninsular India where it meets the drinking water and irrigation needs of millions of people and lakhs of hectares of farm land. The other monsoon, northeast monsoon, begins in October and ends by November. It, however, does not cover as vast an area as the summer monsoon.
Researchers from the Indian Institute of Technology (IIT) Kanpur, and IIT Delhi were also part of the research which focussed on the Indian summer monsoon for the first time. Dr Vijay Kanawade and Abin Thomas were part of the research team from the University of Hyderabad.
As part of the study, the team analysed the long-term satellite data (2002-2016) and reanalysed global data to arrive at the conclusion that aerosols are responsible for the less rainfall. Enhanced accumulation of aerosols within the earth’s boundary layer can further decrease the turbulence in the lower troposphere (region about six km above earth). “This may have climatic effect on moisture transport as well as spatial distribution of clouds and surface rainfall during Indian summer monsoon,” the researchers said.

Aerosols influence the physical properties of clouds. They also affect its radiative properties. The researchers found that aerosol interactions with clouds induce changes to the cloud structure and thereby, have an intensified net cooling effect at the surface.
According to the research, high aerosol pollution results in smaller water droplets.These small droplets instead of falling down as rain gets lofted up with clouds. They then get more ice mass and become convective clouds. Convective clouds then grow upwards till they reach end of troposphere.Then they expand horizontally forming stratiform clouds, resulting in less rainfall.
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About the Author
Syed Akbar

Syed Akbar is a senior journalist from Hyderabad. He is a specialist-journalist in science, technology, health, politics, environment, development, wildlife, religion, communities, and consumer affairs. He has been in the profession for the last 24 years. Before joining The Times of India, he worked with Deccan Chronicle and Indian Express.

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