Climate change adding muscle to cyclones forming over Bay of Bengal

 Hyderabad: Cyclones forming over Bay of Bengal are increasingly getting stronger, and larger, and as a consequence, their impact is being felt in wider areas, as is believed to be the case with Cyclone Michuang that has been dumping heavy amounts of rain over parts of Tamil Nadu, Andhra Pradesh and is expected to do the same over some of Telangana districts.

With climate change resulting in warmer seas and the resultant rise in atmospheric moisture,  heavy rainfall areas extend to greater distances, of even up to more than 300 km around the cyclone centre, according to a December 2022 study published in the Atmospheric Research journal.

 “Globally, the understanding is that cyclones are bringing more rains than they did earlier, largely because of abundant moisture in the atmosphere resulting from warming of oceans and increase in evaporation, Dr Roxy Mathew Koll, climate scientist at the Indian Institute of Tropical Meteorology, Pune said.

He said the increase in area affected by cyclones and because of their growth in size was noticed over the last few decades, and from available data, “we see indications of these becoming larger.” He, however, added that it is not sure if this will be the case in future too but research over the decades has shown that the radius of cyclones, and the moisture they were carrying is on the increase.

The conditions are becoming more conducive for cyclones to hold more moisture, he said.

Incidentally, Bay of Bengal which typically sees four or five cyclones a year, has a “shallow” mixed layer – where warmer water on the surface meets the cooler water of the seas – and the indications are that rising temperatures due to climate change is resulting in increased evaporation and cyclones getting more severe on India’s east coast.

The Bay of Bengal’s mixed layer is around 10 metres from the surface, primarily because of the freshwater flows into the sea from the Ganga, the Mahanadi and other rivers that empty into this sea. Whatever is exposed to solar radiation is largely manifesting on this thin layer, he explained.

According to Climate Trends, an organisation that works on climate change topics, recent observations indicate that cyclones in the north Indian Ocean are intensifying rapidly with wind speeds increasing by more than 50 knots (92 kmph) in just 24 hours where the sea surface temperature is 30 degrees Celsius because of rapid warming of the region. It said that since 2000, frequency of cyclones undergoing rapid intensification in the north Indian Ocean was on the rise. And due to the eastward shift of the points of origin of cyclones over Bay of Bengal, they are travelling for longer periods over the ocean and drawing more of thermal energy released from the warm ocean waters with a potential to develop into very severe cyclones with wind speeds of 65 knots (120kmph), or more, it said.