Simulations of an extreme rainstorm event (1056.7 mm/day) along the South China coast: The effect of single- and double-moment cloud microphysics schemes on precipitation

Abstract

An extreme rainstorm event (1056.7 mm/day) along the South China coast in summer 2018 is investigated using WRF model. We focused on the effects of single-moment WSM6/7 and double-moment WDM6/7 microphysics schemes on the extreme precipitation. (1) The precipitation area, rain band movements and changes in hourly rainfall intensity could be robustly simulated in the 4 experiments. The performance of each scheme varied across different grades of precipitation. WDM7 scheme simulated precipitation extremes and hourly rain intensity that were closest to observations and produced relatively higher scores for light rain; WSM6 scheme had relatively higher scores for moderate rain; and WSM7 scheme showed higher scores for heavy rain and rainstorm. (2) Compared with the single-moment scheme, the double-moment scheme showed higher cloud water and hail mixing ratios. There was no significant difference in cloud water and snow mixing ratios. (3) Schemes incorporating the hail particles showed a larger cloud water mixing ratio but a smaller graupel mixing ratio. Incorporating hail particles caused an increase in simulated precipitation intensity and smaller simulation errors. (4) The increase in graupel mixing ratios was correspondent to the three precipitation peaks. The temporal evolutions of graupel, hail and snow mixing ratios are similar to that of precipitation, with the peak of cloud water mixing ratio appearing earlier than that of precipitation and the peak of ice mixing ratio appearing later than that of precipitation.