By Sanjeev Kumar Patro
Under attack by heat wave for the 3 consecutive years, will 2025 spell any cooler clime when La Nina is predicted to stay on till March 2025?
Bhubaneswar: 2024 summer was the most brutal ever since 2011 in the country with the count of heat wave days rising to a whopping 554. And the eye-popping revelation is Odisha emerged as the nation’s hottest place where the grueling duration of heat wave was 37 days, leaving core hot centres like west Rajasthan, Delhi, Haryana, Punjab, Uttar Pradesh and Madhya Pradesh behind.
As per the data available with IMD, Odisha, along with Gangetic West Bengal are the two regions in the country that have been exhibiting a rise in the duration of heat wave days in the country.
While the heat wave days in West Bengal had risen by around 280%, the rise in Odisha during the period 2022 – 2024 had been 227%. But, the matter of fact is Odisha leads over Gangetic West Bengal in duration of heat wave days in 2022 and 2024.
Sample this. In 2022, the count of heat wave days in West Bengal was 8, 2023 – 27 and 2024 -31. In contrast, the number of heat wave days in Odisha was 11, 24 and 37, respectively.
ODISHA HEAT MAP
The heat map of IMD shows that during the period of 1961 – 2021, western, north coastal Odisha, and places like State Capital Bhubaneswar, Cuttack have been recording a rise in the number heat wave days in a year. But the southern, southwest regions and south east coastal areas exhibited either declining or stable trend over the period of 1961-2021. The central regions of the State like Angul, Talcher et al, which were once the hottest regions, are also indicating a decline in heat wave days over the period.
In fact, data reveals heat wave days in the State capital Bhubaneswar showing an alarming rising trend over the period.
HOTTER CAPITAL
The State Capital is turning hotter over the period. Till the year 2000, the heat wave days’ duration in the city hovered around 10. The first heat wave attack on the city was on 1998, when heat wave days here touched 10, taking a human toll of around 123. 2014 and 2024 recorded the highest heat wave days of around 24 days.
If the overall average trend is to be taken into account, the heat wave days in the city have been on the upswing since 2004.
WHY COASTAL ODISHA SINGE?
As per study done by Indian Institute of Tropical Meteorology (IITM), Pune, warming of Bay of Bengal has to be blamed for the baking heat wave days in coastal regions. The study found increased intensity of marine heat waves in Bay of Bengal in recent years, for which since 2019, the bay has been churning cyclones every summer, amidst grueling heat wave conditions over land.
WHY ‘MERCURIAL’ ODISHA?
When genesis of heat wave in Odisha has been attributed to transportation of hot dry air from west and north- west India, how come then the State experienced more heat wave days than Rajasthan or even say Chattisgarh?
As per a study by weather scientist S Karunasagar , IMD, Andhra Pradesh, rise in heat wave days and conditions in Odisha is attributed to northwesterly or northerly winds generated due to development of north south trough over central parts of India. These winds then lead to dry and stable atmosphere over the Odisha and adjoining states like Andhra Pradesh.
The study observed absence of easterlies (moist winds) from lower troposphere to mid tropospheric level, means from 1.5 km to 5.5 km above sea level, during the heat wave days.
As 2024 was El Nino year, the abnormal SST (sea surface Temperature) of Bay of Bengal has acerbated the weather systems to persist during spring and later, and roast Odisha in the brutal way.
2025 Summer Cooler?
IMD and US NCEP studies reveal that the count of heat wave days in the country, including Odisha, has a relationship with the global phenomenon of El Nino and La Nina. El Nino means more heat wave days, La Nina means lesser.
As the latest ENSO index by US NCEP predicts persistence of La Nina till March 2025, the cooler SST may come into play, and heat wave days may come down.
CAVEAT: In year 2022, La Nina was in place but the country as a whole recorded 467 heat wave days, due to the continuation of north – south trough that usually breaks down in spring. Moreover, the La Nina 'in force' prediction is till March only. Odisha witnessed grueling summer in 2023, when La Nina withdrew from March.
