Changes in surface energy balance and its hydrometeorological variables over Indus-Ganga-Brahmaputra river basins

Estimating changes in the Earth's surface's temperature and energy mass balance has grown importance in the recent decades. The South Asian Himalayas are extremely susceptible to changes in precipitation and hydrological/hydrometeorological equilibrium. Understanding these shifts in the hydrological balance is important for managing water resources, identifying water-sensitive places, and other issues throughout the three main Himalayan River basins, the Indus, Ganga, and Brahmaputra (IGB). They differ greatly in terms of topography, geography, landuse/landcover heterogeneity, seasonal variability, geomorphological features, etc. In order to evaluate surface energy balance and various thermodynamic processes, precipitation, turbulent fluxes, evaporation, potential evaporation, etc., are taken into consideration. For trend analysis, the nonparametric Mann-Kendall method is used, and for change point detection, the Pettitt test is used for data from 1950 to 2020. The mean precipitation difference between 1982–2020 and 1950–1981 indicates a reduction during the monsoon and post-monsoon over GRB and BRB, based on the change point year 1981. In BRB, the changing years of potential evaporation and evaporation have a strong correlation with monsoon, whereas in GRB, this correlation is limited. It illustrates how the two basins land use types differ, with BRB having more forest cover than GRB. The Bowen ratio has a lead-lag relationship with many hydrometeorological factors. Present research findings on changing hydrometeorological variables are significant and can help with planning and policy for the good of society, such as improved management of water resources, possible effects of climate change, etc. This study will help policymakers in better comprehend the shifting precipitation patterns, which will aid in developing new agricultural and water resource sustainability strategies.