Hyderabad: Increased urbanization is possibly causing heavy rainfall in South India, shows a study by the Department of Centre for Earth, Ocean and Atmospheric Sciences at University of Hyderabad. According to the study, the precipitation during heavy rainfall in these states has significantly increased from 2000 to 2017.

Several heavy rainfall events have been reported from cities of South India in the last few years. They include extreme rainfall that created havoc in Chennai and nearby areas in Tamil Nadu in December, 2015, the heavy rainfall over Hyderabad and adjoining areas in Telangana in September, 2016, and the extreme rainfall in Kerala in August, 2018.

These three states differ in their geographical locations, and also the season in which they receive rainfall. Kerala, located on the southwest Indian coast off the Arabian Sea, receives heavy rainfall during the summer monsoon from
June-September. Tamil Nadu, off the Bay of Bengal receives rainfall mainly during the northeast monsoon (October-December).

A team, led by Professor Karumuri Ashok, examined whether a common factor, the changing land use land cover (LULC) in these states, has any implications for the heavy rainfall events. Their findings were reported in the ‘Quarterly Journal of Royal Meteorological Society’ on May 18, 2020.

Using the land use land cover (LULC) data from ISRO, and by conducting 2 km resolution simulation experiments of 12 heavy rainfall events over the states, the researchers found distinct LULC changes in these three states — Telangana, Tamil Nadu and Kerala, which led to higher surface temperatures and a deeper and moist boundary layer.

These in turn caused a relatively higher convective available potential energy and consequently, heavier rainfall, said Professor K. Ashok from the Department of Centre for Earth, Ocean and Atmospheric Sciences, who led the analysis with Ph.D scholar A. Boyaj.

The study also suggests that increasing urbanization in Telangana and Tamil Nadu is likely to enhance the rainfall during the heavy rainfall events by 20-25 per cent. The land-locked state, Telangana, receives the bulk of its annual rainfall during the summer monsoon season.

Professor Ashok feels that improving the density of observational rainfall and other weather parameters may help in forecasting of extreme rainfalls at the city-level.

The work was done in collaboration with Prof. Ibrahim Hoteit and Dr. Hari Prasad Dasari of King Abdullah University of Science and Technology (KAUST), Saudi Arabia.

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