Circulation Features of Persistent Heavy Rainstorm in Sichuan during Main Flood Seasons
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Abstract:
Based on the Sichuan rainstorm hazard and economic loss survey from 1984 to 2010, the daily precipitation data, and NCEP reanalysis data from June to September, 1981 to 2010 in Sichuan, the characteristics of economic loss induced by rainstorm hazard for nearly 30 years are studied and the multiscale circulation background in Sichuan rainstorm hazard is obtained. The results show that rainstorminduced economic losses from 2000 to 2010 over the previous 10 years increased by 80.6%, and the occurrence frequency of rainstorm hazard increased by 38%. The characteristics of rainstorm circulation background form June to September are: South Asia High is stronger in the year of “flooding in west and drought in east” than in the year of “flooding in east and drought in west”; the 586 line of Western Pacific Subtropical High is located in the south of Sichuan and Chongqing; in flood years, Subtropical High has significantly quasibiweekly oscillation cycle from the beginning of July, and the volatility of westerly circulation index is greater. In the middle and upper troposphere at high latitudes, the East Asia atmospheric circulation has a 14day LFO (Low Frequency Oscillation); the Plateau vortex has about 14day turbulence cycle; the southwest flow at low latitudes repeatedly is delivered to high latitudes, and the Bay of Bengal vapor flux is stronger than normal; and the vapor passage into the Sichuan region is unobstructed.
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Supported by:Beijing E-Tiller Technology Development Co., Ltd.
Supported by:Beijing E-Tiller Technology Development Co., Ltd.