Arabian Sea Aerosol-Indian Summer Monsoon Rainfall relationship and its modulation by El-Nino Southern Oscillation

The intensity of Indian summer monsoon rainfall (ISMR) over Central India (CI) is known to be positively correlated with the dust aerosol loading over the Arabian Sea (AS) on short time scales of about a week. However, global oscillations such as the El-Nino Southern Oscillation (ENSO) modulate both the rainfall over India and aerosol loading over the AS. This study uses long-term satellite-based aerosol and gridded rainfall datasets to explore the correlation between AS aerosol and CI rainfall and their relationship to ENSO. It is found that the highest correlation is during El-Nino (0.53), followed by Normal (0.44) and La-Nina (0.34) years, closely following the overall dust aerosol loading over the AS. Spatially, irrespective of the phase of ENSO, the high aerosol loading conditions are associated with increased winds over the AS, shifting eastward towards the Indian mainland and enhancing rainfall over CI and elsewhere across the Indian landmass. In contrast, the low aerosol loading conditions over the AS are associated with reduced winds, shifting westward away from the Indian mainland, suppressing rainfall over CI. In response to anthropogenic climate change, the El-Nino-like conditions are likely to increase in the future, making the dust aerosol-induced monsoon rainfall enhancement/modulation significant.