• CN 62-1175/P
• ISSN 1006-7639

Journal of Arid Meteorology ›› 2021, Vol. 39 ›› Issue (3): 415-425.

Condition of Water Vapor and Multi-scale System During a Continuous Heavy Rainfall Process in Sichuan

SHI Rui1,2, HE Guangbi1, ZHOU Chunhua3

1. 1. Chengdu Institute of Plateau Meteorology, China Meteorological Administration, Heavy Rain and
Drought-Flood Disasters in Plateau and Basin Key Laboratory of Sichuan Province, Chengdu 610072, China;
2. Sichuan Provincial Meteorological Observatory, Chengdu 610072, China;
3. Meteorological Disaster Defense Technology Center of Sichuan Province, Chengdu 610072, China
• Online:2021-06-30 Published:2021-07-16

四川一次持续性暴雨过程的水汽特征及多尺度系统影响分析

1. 1.中国气象局成都高原气象研究所，高原与盆地暴雨旱涝灾害四川省重点实验室，四川成都610072；
2.四川省气象台，四川成都610072；3.四川省气象灾害防御技术中心，四川成都610072

Abstract: A continuous rainstorm process occurred in the west of Sichuan Basin from 8 to 11 July 2018, which lasted for a long time and concentrated in the west of the basin, and resulted in serious flood disasters. Based on NCEP/NCAR reanalysis data, meteorological observation data from conventional weather stations and intensive automatic weather stations of Sichuan, the water vapour condition, dynamic condition and mutil-scale systems of the continuous rainstorm process were diagnosed and analyzed. The results are as follows: (1) The persistent rainstorm took place in favorable atmospheric circulation background. The west Pacific subtropical high moved westward and maintained steadily, which restricted the moving direction and speed of upper trough in the mid-latitude region, and further led to the information of block high over Sichuan Basin. Meanwhile, the pressure gradient between the west Pacific subtropical high and typhoon increased under the gradually moving westward of typhoon ‘Maria’, and the southerly wind in low level strengthened.  (2) The abundant water vapor from the South China Sea was transported to Sichuan Basin, which was the necessary condition for the formation of persistent rainstorms in Sichuan Basin. The southerly wind in the lower troposphere was gradually maintained and enhanced with the moving westward of typhoon. The northeasterly airflow in the west side of typhoon shifted to the southeasterly airflow in the south side of the west Pacific subtropical high, and strengthened in the southeast side of southwest vortex, which formed the obvious airflow convergence, and made water vapor accumulate rapidly. (3) The interaction between multi-scale systems prompted the information and development of southwest vortex, which was a main cause of the maintaining and enhancing at later stage of continuous rainstorm in Sichuan Basin. The westwards extending location and intensity of subtropical high between the southwest vortex and the landing typhoon ‘Maria’ determined the sinking branch of secondary vertical circulation, and further restrained the falling areas of rainstorm.