BENGALURU:A recent study of the Indian monsoon has detected a decrease in its “slow rhythms” and an increase in extreme events.
This means, more water in a shorter span of time. Management of this big volume of water can get difficult in urban areas, as seen from rain events in Bengaluru.
Slow rhythms of the monsoon have decreased over the past 60 years, according to a recent study by scientists at the Indian Institute of Science.
A compensating increase in the number of extreme rainfall events in the monsoon months has also been detected in the study.
The rhythm of the Indian monsoon is set by weeks of continuous rain (active phase) punctuated by weeks with no rain at all (break phase).
“The challenge is to predict seasonal/subseasonal rainfall, which has direct implications for agriculture and disaster management,” says Nirupam Karmakar, the lead author of a study, which has been published in Environmental Research Letters.
“Adaptation to changes in subseasonal variability of rainfall can be harder,” says Karmakar, which makes it important to understand subseasonal changes in the monsoon.
If there are fewer slow pulses, then there are fewer of extreme events too.
The study separated the slow pulses in the monsoon, which last 20 to 60 days from the faster pulses. They found that the intensity of these slow pulses has decreased over the past 60 years.
This decrease has been compensated by an increase in short, high intensity rainfall events.
An increase in extreme events occurred over the coastal regions in the months of May and June and over central India in the months of July and August. Previous studies have documented this increase, but “our main concern was to find how these extreme events are spread (between the active, break and transition periods in a season),” says Karmakar.
A step towards addressing the issue of subseasonal changes in the monsoon in a changing climate has been taken up by this study. The impact of natural variations in climate and human induced climate change is, however, unclear. “The role of natural variability can be hard to detect in 63 years of data. To address (the issue of) climate change, modelling experiments need to be done,” says Karmakar.
Karmakar is a PhD student of Prof Arindam Chakraborty and Prof Ravi Nanjundiah in the Dept of Atmospheric and Oceanic Sciences and Divecha Centre for Climate Change.
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