Short-term modulation of Indian summer monsoon rainfall by West Asian dust

The Indian summer monsoon results from a complex interplay between radiative heating, dynamics, and cloud-aerosol interactions. Despite increased scientific attention, the effect of aerosols on monsoons still remains uncertain. Previous studies (using observational and modeling approaches) have focused primarily on local climate effects on seasonal timescales, but shorter-term and non-local links have not previously been explored or identified. Here we present observational evidence and numerical modeling results to demonstrate a link between aerosols over the Arabian Sea and West Asia and Indian summer monsoon rainfall. Simulations using a state-of-the-art global climate model support this remote link and indicate that variability in dust aerosol loadings influence radiative heating rates that can induce larger scale circulation changes, modulating moisture transport and convergence over central India, and modulate monsoon rainfall on relatively short time scales (about a week). Our model simulations suggest that by heating the atmosphere, dust aerosols induce large-scale convergence over North Africa and West Asia, increasing the flow of moisture over India from the Arabian Sea. Our findings highlight the importance of natural aerosols in influencing the strength of the Indian summer monsoon, motivating additional research in how changes in background aerosols of natural origin may be influencing monsoon precipitation.