Long-term trend analysis of surface temperature over North-East India and adjoining regions based on CRU and ERA5 reanalysis

This study investigated the annual and seasonal mean temperature trends of North-East Indian region and surrounding territories over the period 1901-2020 with special emphasis on the trends from the recent past (1979-2020) utilising Climatic Research Unit (CRU) and ECMWF Reanalysis version-5 (ERA5) data. Spatio-temporal distribution of surface temperature across different seasons and associated biases between 1901 and 2020 were examined. The long-term trend of temperature was evaluated by linear regression for each month from the entire 120-yr period over the whole study domain. Further, Mann-Kendall and Sen's slope test was employed to assess the magnitude of the trend at 11 selected locations of varying altitudes. Areas around Bangladesh, which are notably polluted, as well as Myanmar and the Indian states of West Bengal, Jharkhand, Bihar and Chhattisgarh exhibited notable mean temperatures than the rest of the region. Both near-surface and 2m-temperature displayed positive trends for the period 1901-1950, 1979-2020, and during the whole duration 1901-2020, despite negative trends during 1951-1978. It has been observed that the regions with relatively higher elevations have experienced a larger warming rate than the low-elevation zones.HighlightsAnnual and seasonal temperature trends for North-East India and surrounding territories were studied.Mann-Kendall and Sen's slope test was carried out for 11 selected locations.Post-monsoon season experienced greatest rise in mean temperatures between 1901 and 2020.Temperature data revealed increasing trends for periods 1901-1950, 1979-2020, but decreasing trends for 1951-1978.Warming rates were higher for higher elevation zones, particularly during the postmonsoon and winter months.