Abstract:
Long continuous rainstorm is one of the extremely catastrophic events, and its cause and forecast are of many concerns. April to June is the main rainy season in Guangdong Province, and large scale and long continuous rainstorm can easily induce flood-causing catastrophe. Data analysis shows that long continuous rainstorm lasting for over 7 days causes serious flood disaster. Daily precipitation and rain pattern from 86 meteorological stations in Guangdong Province during 1961—2008 are investigated. The climate characteristics of the annual longest continuous rainstorm is analyzed, and the preceding field of circulation and sea surface temperature (SST) with or without long continuous rainstorm are studied using composite analysis and correlation analysis.The results show that the longest period of heavy rain days in Guangdong Province mainly manifests inter-decadal stage change with weak linear increasing trend. The longest period of heavy rain days in Guangdong Province are less from the mid-1970s to the 1980s than that in the other period, and long continuous rainstorm that continues for more than 7 days occurs mostly after the year of 1990.The 500 hPa height field characteristics during long continuous rainstorm are high in the west and low in the east at high-latitudes, and high in the east and low in the west at low-latitudes. European trough deepens at mid and high-latitudes and a clear ridge occurs around Balkhash and Baikal. These results show that the meridional circulation is strong and cold air is frequently active. South branch trough is active at low-latitude and subtropical high is strong. These distributions are advantageous to meeting of cold and warm air along the coast of South China Sea and form long continuous rainstorm. SST anomalies (SSTA) in Niño4 region is negative, SSTA in Niño3 region is weak positive, SSTA in the Kuroshio region is clearly positive, and SSTA in West Wind Drift region is weaker negative in composite SSTA with long continuous rainstorm. The composite difference of 500 hPa geopotential height and SST in March and April between long continuous rainstorm and no long continuous rainstorm shows that they have significant distinction. It also reveals that SST fiercely evolve from March to June and SSTA in Niño3 and Niño4 regions changes from negative to positive value for long continuous rainstorm, but distributive pattern of El Niño SSTA persists from March to June for no long continuous rainstorm.