Impact of vegetation on the boreal summer monsoon precipitation over India: an energetics viewpoint.

The heterogeneities arising out of surface variabilities, land-sea contrasts, aerosol concentrations, and the influence of orography define the intricate characteristics of regional monsoon systems. The amount of precipitation India receives during the boreal summer monsoon season can be modulated by land surface processes due to its influence on moisture availability and atmospheric stability. This study investigates the impact of vegetation changes on the seasonal mean precipitation over Indian land using fully coupled global climate model (GCM) simulations with idealized land cover. In addition, an  energetics framework is employed to unravel the physical mechanisms/pathways connecting vegetation and rainfall. In general, evaporation enhances with an increase in forest cover. However, this does not translate to a similar increase in all-India averaged precipitation. Using the energetics approach, we find that precipitation changes primarily happens via three different thermodynamic pathways. We also find the regions where each pathway is dominant. The relative dominance of these pathways in various areas leads to spatial inhomogeneities in the precipitation response due to vegetation changes. Human intervention, including agricultural expansion, has reshaped the landscape of India in the last century, altering the nature of land-atmosphere interactions. The results from this study, that land cover plays a significant role in modulating the regional characteristics of seasonal monsoon precipitation, are particularly important in this context. The findings in this study also have broader ramifications since the dominant region-specific mechanisms identified are expected to be valid for other forcings and are not just limited to the scenarios considered here. A unified framework connecting these various forcings with monsoon variability would be of great practical importance, and the present study is an advancement in this regard.