Comprehending dust aerosol impacts on cloud and rainfall distribution during a ‘dust-rain’ storm through WRF-Chem simulations

A severe thunderstorm was observed in the northern Indian region during an intense dust storm in May 2018. The current study investigated the impacts of dust particles in altering the thermodynamics, dynamics, cloud characteristics, and precipitation considering this unique extreme event by utilizing various observational and reanalysis datasets, a meteorology-chemistry model, namely ‘WRF-Chem’, and the Lagrangian transport model ‘HYSPLIT’. WRF-Chem model performed reasonably in replicating aerosol, meteorology, and rainfall characteristics while exhibiting some biases. Desert dust and polluted dust are the predominant aerosol types that can ascend even up to 12 km as per the severity of the storm. HYSPLIT trajectories suggest that they were primarily transported to northern India from both the near-surface or elevated layer over the Thar Desert and its neighboring areas. While analyzing the aerosol-radiation interaction (ARI) and the aerosol-cloud interaction (ACI) of dust, it is realized that they exhibit almost opposite behavior in all circumstances when it comes to altering thermodynamics, dynamics, clouds, and rainfall distribution. Interestingly, the intense mid-tropospheric heating due to dust-induced ARI increased both moisture convergence and upward water vapor transport, consequently favoring the production of more precipitating hydrometeors (20–30 g kg−1) and increasing convective rainfall (up to 20 mm) over some places. However, ACI typically inhibited deep convection over most places except some high-terrain regions, providing extra fuel for updraft through orographic lifting and experiencing marginal rainfall. ARI was realized to be the dominant contributor during the intense rain event, even if the contrasting nature of dust-induced ACI somewhat offsets the overall impacts.