海河流域极端暴雨特征及其天气成因

Characteristics and Weather Cause of Extreme Rainstorms in Haihe River Basin

利用海河流域实测和调查年最大点暴雨、实测大面积暴雨和气象等资料，分析了年极端点暴雨的季节变化、特征和地区分布、大面积暴雨特征以及形成极端暴雨的天气成因，揭示了极端暴雨发生的基本规律。结果表明，流域暴雨9成以上集中在7-8月，极端暴雨7成高度集中在7月下旬到8月上旬：极端暴雨集中分布在太行山一燕山山脉的迎风山区：短历时小面积极端暴雨则分布在高原区：极端暴雨的年际变率迎风山区最大，平原和高原区较小；流域性极端暴雨高空环流多为经向型，通过中纬度西风槽、副热带高压或台风等天气系统以及迎风山区地形抬升作用共同造成。

Based on the observed and investigated annual maximum point rainstorms, observed large-area rainstorms and meteorological data, we analyzed the seasonal variation, characteristics and regional distribution of annual extreme point rainstorms, the characteristics of large-area rainstorms, and the weather cause of extreme rainstorms in Haihe River Basin, so as to reveal the basic law of extreme rainstorms occurrence. The results show that 90% of the rainstorms in the Haihe River Basin occur in July and Autumn, and 70% of the extreme rainstorms appear between late July and early Autumn. The distribution of extreme rainstorms concentrated on the windward slope of Taihangshan-~anshan Mountains, while that of the short-time and small-area extreme rainstorms located in the plateau area. The maximum value of the rainstorms interannual variations exist in the windward mountain area, and the lesser value exist in the plain and plateau area. The upper air circulation of most basin-wide extreme rainstorms is in warp direction, and the rainstorms usually happen under the combined action of weather systems, such as middlelatitude westerly trough, subtropical high and typhoon, and topography uplift of the windward mountain.