Investigation of meteorological variables and associated extreme events over North-East India and its adjoining areas using high-resolution IMDAA reanalysis

The study incorporates a first-time investigation of annual trends in precipitation, maximum and minimum temperature, and related extreme events across a set of 21 study sites of differing altitudes across North-East India and its contiguous areas employing reanalysis datasets of highest spatial and temporal resolution (0.12º, 1-hr) available for Indian subcontinent called Indian Monsoon Data Assimilation and Analysis (IMDAA). A total of ten precipitation and eleven temperature extremes, following the Expert Team on Climate Change Detection and Indices (ETCCDI), have been explored for trend identification at 5% and 1% significance levels combined with change point analysis using the Mann-Kendall (MK)/modified MK (mMK) tests and cumulative sum (CUSUM) charts, respectively. Noteworthy findings were revealed, where most stations exhibited significant annual increases in minimum temperatures (Tmin), along with a less pronounced trend in maximum temperatures (Tmax), while some stations showed decreasing annual precipitation. Results revealed predominant significant increasing trends in temperature indices across most of the locations with indices related to warmer nights showing greater significance. However, precipitation indices showed declining trends for most of the sites except for one location. Change points corresponding to minimum and maximum temperatures characterized by negative to positive shifts outnumbered those to precipitation, which showed rather opposite shifts across most of the locations. Predominant negative to positive shifts were observed in summer days (SU25), tropical nights (TR20), annual maximum of daily Tmin (TNx), warm days (TX90p), warm nights (TN90p), annual minimum of daily Tmax (TXn) and Tmin (TNn), whereas positive to negative in annual maximum of daily Tmax (TXx), cool days (TX10p), cool nights (TN10p) and diurnal temperature range (DTR) indicating a greater rise in warming scenario rather than cooling scenario. Precipitation indices generally shifted from positive to negative values, except for consecutive wet days (CWD), which indicates shifting precipitation patterns. The rise in extreme events poses a serious threat to the region and the continuously evolving pattern of climatic variables may have significant implications on human and natural ecosystems over this area of Indian subcontinent.