The Effect of Mineral Dust on Microphysical Properties of Hailstorm in Northwest China

Mineral dust can act as ice nuclei (IN) and form ice crystals, and at the same time dust particles mixed with sulfate and hygroscopic materials can also act as cloud condensation nuclei (CCN) and affect the warm processes during their long-range transport. In this study, the heterogeneous ice nucleation schemes in the Weather Research and Forecasting model coupled with a spectral bin microphysics (WRF-SBM) have been improved, which could considered aerosols acting as both CCN and ice nuclei (IN). A hail storm occurred around Tianshan mountains, northwestern China was simulated with updated WRF-SBM. Further, four sensitive simulation tests were conducted with different cloud condensation nuclei (CCN) and IN concentrations to investigate their respective roles during the evolution of the hailstorm. The increase in CCN concentration resulted in larger cloud droplet concentration and cloud water content, as well as enhanced condensational growth which released more latent heat and led to stronger updraft at lower levels. The increase in IN number almost did not affect warm processes, but led to larger ice crystal concentration and enhanced Bergeron process. Larger CCN concentration led to larger supercooled liquid water content, which in turn contributed to the enhanced hail growth by more efficient drop-ice collisions and led to larger size of hail particles, while larger IN number reduced the size of graupel and suppressed the growth of hailstones.