Recent Changes in Temperature Extremes and Heat Stress over Eastern India

The rise of extreme heat events and increase in heat stress under changing climate has been a major concern in recent periods. The present study has been undertaken to analyze temperature extremes and heat stress patterns over Eastern India during the period 1981-2020 for April, May, and June (AMJ). Six indices namely, Monthly maximum value of daily maximum temperature (TXx), Monthly maximum value of daily minimum temperature (TNx), Monthly minimum value of daily maximum temperature (TXn), Monthly minimum value of daily minimum temperature (TNn), Percentage of days when maximum temperature > 90th percentile (TX90p) and minimum temperature > 90th percentile (TN90p) have been utilized to assess the changes in temperature extremes. Furthermore, three heat stress indices (HSIs) namely, Humidex, Simplified Wet-Bulb Globe Temperature, and Apparent Temperature have been used to estimate and categorize heat stress levels. Mixed results with both increasing and decreasing trends over different parts of the study area have been observed during three months in case of TXx, TXn, TNx, and TNn. During AMJ, there has been amplification in the frequency of TX90p over coastal regions of West Bengal and Odisha in latest decades. Increasing TN90p frequency has been found over Sikkim, Bihar, and North Bengal while it has decreased over Chhattisgarh and Odisha. The frequency of strong heat stress has intensified over Gangetic West Bengal and Bihar during recent decades. Spatial coverage of strong stress has also gradually extended and the area under no stress has decreased during AMJ season.