A Study of Cloud Microphysical Processes Associated With Torrential Rainfall Event Over Beijing. Issue 16 (18th August 2018)

• Record Type: Journal Article
• Authors: Mao, Jiahua; Ping, Fan; Yin, Lei; Qiu, Xinfa
• Is Part Of: Journal of geophysical research. Volume 123:Issue 16(2018)
• Page Start: 8768
• Page End: 8791
• Publication Date: 2018-08-18
• Subjects: cloud microphysical processes -- warm‐sector precipitation -- cold‐frontal precipitation; Atmospheric physics -- Periodicals; Geophysics -- Periodicals; 551.5
• DOI: 10.1029/2018JD028490
• Languages: English
• ISSNs: 2169-897X

Abstract

Abstract: The evolution of mesoscale convective systems (MCSs) leading to a heavy rainstorm event that occurred in Beijing on 21 July 2012 was simulated using the Weather Research and Forecasting model. Observational analyses indicated that this event can be divided into an earlier‐occurring warm‐sector precipitation (WSP) and a later‐occurring cold‐frontal precipitation (CFP). Owing to the considerable differences in their ambient weather conditions, the features and evolution of the cloud microphysics were different. Diagnoses of the mass‐ and heat‐hydrometeor budgets showed that the major differences in rainwater source were that the graupel melting (PGMLT) and the collection of snow by rain (PRACS_s2r) had similar magnitudes in the WSP, and PGMLT was larger than PRACS_s2r in the CFP, while the accretion growth of cloud droplets (PRA) was always the largest in both phases. The main cooling effect in the WSP was due to the evaporation of rainwater (PRE) and cloud water, while it was PRE and PGMLT for the CFP. The mechanisms of how microphysical processes influenced the precipitation were explored. It was found that the strong PRA in the WSP was conducive to the formation of a supercooled water level and evoked a seeding effect. However, graupel processes were crucial for the CFP. The strong sublimation processes of graupel and snow associated with the collection of droplets by graupel caused more latent heat release and drove airflow to reach a higher convection height. Moreover, the stronger PGMLT cooled the air in the MCS and reduced the effect of cloud droplet accretion growth. Key Points: The PRA was the biggest source of the rainwater in both WSP and CFP. Compared with the WSP, the PGMLT of CFP was stronger and important The considerable PRA in the WSP formed a supercooled water level where seeding processes occurred obviously In the CFP, higher latent heat release in the upper levels caused strong updrafts, while reduced PRA occurred in the lower levels