春秋季环流的季节性调整对湖北省夏季洪涝的影响

EFFECT OF SEASONAL CIRCUMFLUENCE DRESSAL IN SPRING AND AUTUMN ON SUMMER FLOOD IN HUBEI PROVINCE

洪涝是湖北省的主要气象灾害 ,文章在对湖北省汛期降水气候特征分析的基础上 ,定义出 9个湖北持续性暴雨洪涝年 ,这些洪涝年主要发生在中国东部出现南方类或中间类雨型。通过对湖北省东部地区汛期降水与 5 0 0hPa高度场的相关分析 ,认为春秋季节的环流调整异常 ,是预测湖北省汛期降水的重要前期因子 ,典型洪涝年和干旱年前期 3月份在 5 5°～ 65°N的纬圈上 ,其高度距平合成显示 ,在 1 30°E～ 1 2 0°W范围内和 90°～ 1 0°W范围内距平变化相反。通过对上年春季 3月、秋季 1 0月及当年 3月 5 0 0hPa高度场上环流季节性调整的分析 ,找出对湖北夏季降水异常偏多具有指示意义的指标 ,建立了湖北省夏季洪涝年的短期气候预测模型。模型首先用两个因子将大涝这种小概率事件 ( 9/49=1 8% )转变为大概率事件( 9/1 3=70 % ) ,然后 ,分两步进行判断。其模型对湖北大涝年 (共 9年 ,1 95 4 ,1 969,1 980 ,1 983,1 987,1 991 ,1 996,1 998,1 999年 )的识别率为 1 0 0 % ,2 0 0 0～ 2 0 0

Flood is the major meteorological disaster of Hubei province. Nine lasting torrential rain flood year are defined after analysis on climatic characteristics of precipitation in the flood period in Hubei province, which occur mainly in years when there is a southern or middle rain-type in the eastern China. The correlation between the rainfall in the eastern Hubei in the flood period and 500hPa circumfluence elevation field is analyzed. It concludes that abnormal redressal of circumfluence in spring and autumn is an important prophase factor in forecasting rainfall in the flood period in Hubei province. A departure composing demonstrates that, in typical flood year and draught year, the departure from average of the heights at 55°-65°N in preceding March is inverse within 130°E-120°W and 90°-10°W. The 500hPa circumfluence feilds of preceding March of the year and March, October of the year before are studied to find out some key indexes which make senses on the abnormal excessive summer rain in the province. Then a short-term climatic forecasting model for summer flooding year in the province is established. The model utilizes two factors to transfer serious flood as a small probability (probability=18%) occurrence into a big probability (probability=70%) occurrence, after that,a judgment is made through two steps, which demonstrates a 100% distinguishing rate for the serious flooding year in history of Hubei province, and the test forecast for 2000-2002 accorded well with actual conditions.