Indian dust-rain storm: Possible influences of dust ice nuclei on deep convective clouds

Estimating the influence of dust aerosol on clouds, especially deep convective clouds which is closely related to heavy precipitation, still has large uncertainties due to the lack of adequate direct measurements. In this study, a typical dust storm along with thunderstorm (referred to dust-rain storm), occurred in Northwest India on May 2, 2018, was selected to explore the possible effects of dust aerosol on deep convective cloud by combining a series of satellite retrievals and reanalysis data. Results showed that dust aerosol and moisture were carried to Northwest India by southwesterly wind at 700 hPa and easterly wind along south foothill of Himalayas at 850 hPa, respectively, and then were lifted to upper level of the cloud by robust updraft induced by the deep convection and secondary circulation driven by the upper-level westerly jet. The injection of dust is likely to transfer supercooled water cloud into ice cloud as effective ice nuclei, hence increasing the cloud ice water path and cloud optical depth but decreasing ice particle radius in the cloud. The latent heat released by this phase-change process would enhance the deep convection and further cause heavy rainfall in northern India by drawing moisture from surrounding region. Although we cannot eliminate the effect of large-scale dynamics, this study highlighted the role of dust aerosol in invigorating the deep convective clouds as ice nuclei, providing observation evidence for the investigation of aerosol-cloud-precipitation interaction.