考虑降雨空间异质性的动态临界雨量预警指标推求

降雨空间分布的不均匀性对中小河流洪水预警的临界雨量有较大影响,而降雨的空间分布难以准确量化,成为制约洪水预警精度的重要难题。结合泰森多边形和等流时面,提出一种既能反映降雨空间分布不均匀程度,又能反映降雨中心位置的降雨空间异质性指数SHIP,进一步基于支持向量机的分类原理,将SHIP用于中小河流洪水动态临界雨量预警指标的推求。以汉江旬河上游为例,分析了降雨空间异质性对临界雨量及预警精度的影响。结果表明,降雨中心越靠近下游,临界雨量越小,若不考虑降雨空间分布的差异性,则可能会出现漏报的风险。由于间接考虑了流域的调蓄作用,引入SHIP推求的临界雨量指标可以显著提高洪水预警的精度。

Study on dynamic critical rainfall warning index considering spatial heterogeneity of rainfall

The non-uniformity of the spatial distribution of precipitation has a great impact on the critical precipitation of flood warning for medium-and small-size rivers, and the spatial distribution of rainfall is difficult to accurately quantify, which has become an important problem that restricts the accuracy of flood warning. Combining Tyson''s polygon and inter isochrone areas, a spatial heterogeneity index of precipitation (SHIP) that can reflect both the degree of spatial distribution and the center of precipitation is proposed. Based on the classification principle of support vector machine, SHIP is used to derive the dynamic critical rainfall indicator of flood warning. Taking the upper Xunhe River in the Hanjiang River as an example, the influence of spatial heterogeneity of precipitation on critical rainfall and early warning accuracy was analyzed. The results show that the closer the rainfall center is to the downstream,the smaller the critical rainfall is,the risk of underreporting would occur if the spatial heterogeneity of precipitation is not considered. Due to the indirect consideration of the regulation and storage of the basin,the introduction of the critical rainfall index estimated by SHIP can significantly improve the accuracy of flood warning. In addition, the proposed SHIP is not only suitable for flood warning, but also can be used for flood forecasting and drought warning,which need to consider the spatial heterogeneity of precipitation,it has broad application prospects.