Long-Time Variation and Mechanism of Surface Energy Budget Over Diverse Geographical Regions in Pakistan

Earth's energy budget is a major force that drives global climate. The long-term pattern of land surface energy budget with pronounced biophysical effects on climate was normally ignored at a regional scale, particularly in Pakistan. In this article, the land surface energy budget from 2001 to 2018 was estimated and analyzed from Moderate Resolution Imaging Spectroradiometer (MODIS) and Cloud and the Earth's Radiant Energy System (CERES) observations over three geographical regions (northern highlands, Indus plains, and Bolochistan plateau) in Pakistan. Biophysical and energy budget parameters, such as Land Surface Temperature (LST), albedo, emissivity, and Normalized Difference Vegetation Index (NDVI), were obtained from MODIS, whereas the downward shortwave solar and longwave thermal radiation were obtained from CERES satellite data. Spatiotemporal trends of three energy budget parameters, i.e., net radiation, latent heat flux, and sensible heat flux, and three biophysical parameters, i.e., albedo, NDVI, and LST, were investigated from 2001 to 2018. The latent heat flux showed a significant increase with a trend of 0.24, whereas a decrease in sensible heat flux with a trend of -0.21 was observed over Pakistan. Net radiation showed an ignorable increase with a trend of 0.054 over the whole of Pakistan. A significant negative relation was found between net radiation and sensible heat flux with albedo, whereas a significant positive relation was found between latent heat flux and NDVI. Biophysical parameters, such as NDVI, albedo, and LST, successively explain the trends of radiative and nonradiative fluxes. This study comprehensively explains the mechanism and patterns of the regional energy budget.