ISSN 1000-0526
CN 11-2282/P
CN 11-2282/P
Archive > Volume 41 Issue 2 > 2015,41(2):143-152. DOI:10.7519/j.issn.1000-0526.2015.02.002 Prev Next
Circulation of Extreme Rainstorm and Its Anomalous Characteristics During Post Flood Period of the Last Decade in Hainan Island
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Abstract:
With daily precipitation observation data in Hainan compiled by National Climate Centre of CMA and NCEP/NCAR reanalysis data, the atmospheric circulation of extreme rainstorm and its anomalous characteristics during post flood period late rainy season in Hainan Island in the last ten years are investigated. Results show that the circulation configurations of extreme rainstorm cases have many similar characteristics. In the upper level, South Asia high is located in the north of South China Sea (SCS) and provides strong divergence. In the middle and lower levels, increasing pressure gradient induced by the interactions among tropical disturbances, the Northwest Pacific subtropical high (NWPSH) and East Asia middle latitude trough are helpful to the formation of frontal zone, maintenance and reinforcement of tropical disturbance and induction of easterly low level jet. The presence of strong low level jet in north central South China Sea is the most significant feature of extreme rainstorm cases in late rainy season, which consists of the southeast wind from the northeast side of tropical disturbance, the northeast wind from the front of cold high and the easterly wind from the south side of NWPSH. The core of low leve jet shows three obvious characteristics of moving from east to west, daily gradual rising and strong wind speed fluctuation before the torrential rain occurs. The distinct characteristics are also manifested mainly in the anomalies of synoptic scale circulation of extreme rainstorm cases in comparison with the same period climatological mean: the Pacific intertropical convergence zone (ITCZ) is exceptionally active, SCS summer monsoon trough and Indian summer monsoon trough are stronger and retreat more slowly in comparison with the normal climatological means. The location of South Asia high is abnormally eastern and southern, and the intensities of middle latitude trough and NWPSH are stronger than usual. The water vapor causing the enhancement of precipitation is transported by the northeast wind from the front of cold high and the easterly wind from the south side of NWPSH.
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