2003年淮河流域大水期间体积降水量的研究

A STUDY OF VOLUMETRIC PRECIPITATION DURING THE HUAIHE RIVER BASIN FLOODS IN 2003

针对 2 0 0 3年梅雨期淮河流域大水提出了体积降水量的概念及其计算方法 ,在计算出淮河流域和其各子流域逐日和总体积降水量的基础上 ,将体积降水量与水文站的水位和流量进行了对比分析。结果表明 :水位对累计体积降水量有较好的即时响应 ,流量对体积降水量有较好的延迟响应。另外 ,讨论了流域体积降水量的预报问题 ,用国内外数值天气预报产品和中央气象台指导预报产品 ,进行了流域体积降水量预报试验 ,并对预报结果进行了检验分析。结果表明 :在目前天气预报水平条件下 ,利用数值天气预报和中央气象台业务预报产品制作体积降水量是可行的 ,能够延长洪水预报的预见期 ;而且 ,数值天气预报产品在预报体积降水量方面有明显的优势 ,因此可以直接利用数值天气预报产品进行体积降水量的客观预报 ,为防汛工作提供重要的依据。

The concept of volumetric precipitation (V) and its calculation methods are studied in this paper based on the Huaihe River Basin Floods in 2003.V is defined as total precipitation amount from sky at a volumetric amount over an area A: V=∫_AP(x,y)dA=∫∫P(x,y)dxdyThe unit of V is m3. V is important information not only to hydrology, flood control and water resource management, but also to verification of precipitation forecasts of numerical weather prediction models and to climate research. Various calculation methods of V are discussed on various distributions of sub-areas. Daily and total V of the whole basin and 7 sub-basins of Huaihe River are calculated and compared with water levels and stream flows. The total V of the Huaihe River Basins during the floods from 00UTC of 21 June to 00UTC of 22 July 2003 was about 1275.62×108m3 which was brought by 5 periods of rainfall caused by 7 heavy rain processes according to the study. In July 2003, 4 of hydrological stations along the Huaihe River reported that the water levels recorded over the warning level near one month. The study indicates that V can represent rainwater amount over the Huaihe River basins during the flood in 2003. V have good correspondence with flow flux and water levels. The water levels of the River show timely responses for accumulate V while the stream flows postpone. It means V may play an important role in flood control and calamity precaution. We also discuss V forecast issues in this paper. An operational V prediction system is introduced, which is based on various numerical weather prediction (NWP) outputs and official forecasts. The verification of V forecasts indicates that it is available to predict V based on NWP output and operational official forecasts. From the analyses on the problems of NWPs and official forecasts, we can see that the official forecasts seem to be not better than NWP products when it is used to produce V forecast, therefore, V may be forecasted with NWP precipitation output directly. V based on precipitation outputs of NWPs of Japan, Gernman and China T213 have good forecast results to the rainstorms. On the view of a hydrologist, V forecasts are better than precipitation one for single point and show a possibility to extend the expect time of a flood prediction. It is also suggested that V based on T213 model output is higher than ones based observation, which means a little over estimation of precipitation forecasts by T213 model.