Changes in patterns of extreme temperature distribution across different regions in India

Global studies of extreme temperature suggest that in recent times there has been an increase in frequency and intensity for hot temperature and decrease for cold temperatures  while a few others show an increase in both warm and cold extremes in the last decade of the twentieth century. Previous research on large scale climate projections show an amplified increase in the highest percentile of maxima and minima, with respect to the lowest percentiles of temperature extremes. The indices recommended by the Expert Team for Climate Change Detection Monitoring and Indices (ETCCDMI) to analyse trends of extreme climate are pertinent to policy and decision making with regard to impact and adaptation studies. While literature is abundant with large scale evaluation of trends in extreme temperatures, there is a want of studies in the regional patterns and distribution of temperature extremes in India. Although India is widely known as a tropical country, the diversities found in the topography of the regions from north to south and east to west, renders microclimate unique to each region leading to disparate inter-annual temperature ranges across the country. So, it is important to explore how regional trends in the different climatic zones of the Indian subcontinent correspond with each other in view of its unique climatic regimes. A comprehensive analysis of temperature extremes in the urban agglomerates and their suburban and rural counterparts is relatively unexplored for India. The results offer insights on the change in the percentile based indices recommended by the IPCC as well as summer and winter maximas and minimas for the entire India over the last several decades. The frequency and intensity of extreme temperatures characterised by number of days less than 10th percentile and more than 90th percentile, and minimum annual minimum temperature and maximum annual maximum temperature respectively, of the distribution over the last six decades have been assessed. The findings of this study suggests that warmer extremes follow an increasing trend, while the colder extremes exhibit no significant trend. However, the trends appear to be spatially coherent irrespective of the extent of urbanization.   Additionally, change in maximum and minimum percentiles of summer and winter temperatures are assessed between the first half of the last century and  the later half of the last century, for the entire country. It was found that change in highest percentiles in both summer and winter minima is more pronounced than lowest percentiles, while increase in highest percentile is more amplified for summer and winter maxima.