Numerical simulation and analysis on cloud microphysical characteristics during a Meiyu heavy rainfall event in Hubei province

Abstract

Affected by a trough and shear line, a Meiyu heavy rainfall event occurred in Hubei Province from June 27th to 28th in 2020, resulting in severe disasters and significant economic losses.. To investigate the impact of microphysical processes on Meiyu front heavy rainfall and improve the forecasting and warning capabilities, the heavy rainfall case was simulated utilizing the regional model WRF 3.4.1, and the effect of cloud microphysical characteristics on the heavy rainfall was discussed. Results are as follows: (1) The heavy rainfall area and evolution of area-averaged precipitation were simulated well with a little overestimation. At the same time, the mesoscale systems were reproduced well through model results. (2) When rainfall strengthened rapidly, melting of ice phase hydrometeors (Melt) contributed more to the growth of rain drop than accretion of cloud droplet by rain drop (CLcr) and the composite radar echo developed rapidly. When the rainfall strengthened a little more smoothly, the amount of CLcr was larger than that of Melt. All the hydrometeors grew significantly and the composite radar echo intensified dramatically. Ice crystals grew more rapidly than snow and graupel. Before the peak rainfall, the content of hydrometeors (except snow), updraft and composite radar echo had reached extreme values. The center of updraft is more consistent with the area of large values of ice-phase particles and cloud droplets content, which is favorable to the riming process. Ice, graupel and the amount of water vapor condensation reached their maximum content and the composite radar echo began to decay before the strongest precipitation occurred. (3) Less ice phase hydrometeors collected cloud droplet was produced than CLcr. Auto conversion of cloud droplet to rain increased significantly when the rainfall process decayed. The main pathway of ice phased hydrometeors was Bergeron process in the initial stage of the precipitation. With the growth of ice phase hydrometeors, riming process between cloud droplet and ice phase hydrometeors was dominant until the heavy rainfall process ended.

Keywords

• meiyu front heavy rainfall
• numerical simulation
• cloud microphysics
• sink and source terms