Energy-Balance Decomposition of the Aerosol-Induced Changes on Surface Temperature Over South Asia

Aerosol-radiation interactions decrease the solar radiation reaching the surface, which cools the surface and influences land-atmosphere interactions and affects the regional climate through various pathways. To estimate the change in radiative and nonradiative fluxes due to aerosol-radiation interactions, regional climate model simulations were carried out over the South Asian region. Using the energy balance equation, aerosol-induced changes in surface temperature are decomposed into its radiative (shortwave (SW) and longwave) and nonradiative (sensible heat flux (SHF), latent heat flux (LHF), and ground flux) components for different seasons. This study showed that the surface cooling due to the decrease in SW radiation is mainly compensated by the decrease in SHF in all seasons. The decrease in SHF is more than 50% of the decrease in SW radiation due to aerosols over the Indo-Gangetic Plain (IGP). Aerosol-induced changes in incoming longwave radiation have a cooling effect over the Indian region except over the western part of South Asia. The aerosol-induced changes in LHF are highly heterogeneous and insignificant except for monsoon season. Over IGP, the decrease in LHF compensates nearly 15% of the SW cooling due to aerosols during monsoon season. Over the Indian region, approximately 40%–50% of the SW cooling due to aerosols is translated to net change in surface temperature, whereas the remaining is adjusted by the decrease of SHF and LHF. Notably, the impact of aerosol-induced weakening of SHF remains unexplored but holds profound implications for the hydroclimate and air quality of the Indian subcontinent.