Several cities across the county faced sudden bursts of heavy rainfall in the last few years especially across south India. This include the extreme rainfall over Hyderabad and adjoining regions in Telangana in September 2016, the August 2018 floods in Kerala and the Chennai deluge of December 2015.
A study taken up by the Centre for Earth, Ocean and Atmospheric Sciences of the University of Hyderabad led by Prof. Karumuri Ashok suggests that increasing urbanisation in Telangana and Tamil Nadu is likely to enhance the rainfall during heavy rainfall events by 20- 25%. These three States differ in their geographical locations - Kerala, located on the southwest Indian coast off the Arabian Sea receives heavy rainfall during the southwest monsoon from June to September. Tamil Nadu, off the Bay of Bengal receives rainfall mainly during the northeast monsoon (October-December). Land-locked Telangana receives bulk of its annual rain during the southwest monsoon season.
The research team including his Ph.D. student Boyaj the 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 18 May 2020.
Their study showed that precipitation during heavy rainfall events in these states has significantly increased from 2000 to 2017. Using the LULC data from Indian Space Research Organisation (ISRO), and by conducting 2-km resolution simulation experiments of 12 heavy rainfall events over these states, the researchers found distinct LULC changes in these three states, 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. Prof. Ashok feels that improving the density of observational rainfall and other weather parameters may help in forecasting extreme rainfalls at the city level. Prof. K. Ashok and Mr. Boyaj- who is the first author, completed the work in collaboration with Prof. Ibrahim Hoteit and Dr. Hari Prasad Dasari of King Abdullah University of Science and Technology (KAUST), Saudi Arabia, according to a UoH spokesperson.
