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A growing body of research has underscored the radiative impact of mineral dust in influencing Indian summer monsoon rainfall variability. However, the various aerosol-cloud-precipitation interaction mechanisms remain poorly understood. Here we analyze multisatellite observations to examine dust-induced modification in ice clouds and precipitation susceptibility. We show contrasting dust-induced changes in ice cloud regimes wherein despite a 25% reduction in ice particle radius in thin ice clouds, we find similar to 40% increase in ice particle radius and ice water path in thick ice clouds resulting in the cloud deepening and subsequently strengthened precipitation susceptibility, under strong updraft regimes. The observed dust-ice cloud-precipitation interactions are supported by a strong correlation between the interannual monsoon rainfall variability and dust frequency. This microphysical-dynamical coupling appears to provide negative feedback to aerosol-cloud interactions, which acts to buffer enhanced aerosol wet scavenging. Our results underscore the importance of incorporating meteorological regime-dependent dust-ice cloud-precipitation interactions in climate simulations.

Plain Language Summary The Indian summer monsoon is the central source of freshwater availability to the densely populated regions of southern Asia. The monsoon circulation and rainfall variability are widely known to be governed by large-scale atmosphere-land-ocean dynamics, meteorological processes, and air-sea interactions. In the past two decades, the role of atmospheric aerosols has emerged as a source of modulating monsoon rainfall, as suggested by a host of climate modeling studies. In this paper, we have investigated a new aspect of aerosols in possibly influencing monsoon clouds and rainfall by specifically examining interaction between mineral dust aerosols and ice clouds, as part of the monsoon system. Using state-of-the-art information derived for aerosols and clouds from multisensor and disparate satellite observations spanning 11 years, we find characteristic signature of dust aerosol-induced modification of thick ice clouds (so-called cloud invigoration effect) toward strengthened susceptibility of monsoon precipitation. Overall, our results shed new light on the potential role of dust and ice cloud interactions in modulating the Indian summer monsoon.