山区流域暴雨洪水的数值模拟

基于中尺度天气研究预报模式WRF和流域水文模型对我国夏季山区的暴雨洪水进行模拟研究。首先,结合新安江水文模型和TOPMODEL自主研发了一个动态结合地面地下产流计算的新水文模型XXT,并选取成熟的天气研究预报模式(WRF)的模拟结果作为XXT的输入进行洪水模拟。其中WRF模拟采取3重区域嵌套模拟再现了2007和2008年夏季山东南部沂沭泗河流域的3次暴雨过程。模拟结果表明,WRF对暴雨的时空分布有较好的模拟与预测能力,模拟结果与观测一致性较好,逐时降水过程较观测更为连续,峰值有一定差异,总量略有偏大。WRF模拟的逐时站点表层土壤湿度与自动站观测的变化趋势一致,峰值偏大,空间分布与降水有着较好的响应关系。总格点径流深的计算结果同样与降水对应得较好,基本能重现出暴雨-径流过程的时空变化特征。其后,利用收集的实测降水资料率定XXT的模型参数,进而将WRF模拟的降水和潜在蒸散发输入到XXT进行流域出口洪水流量的模拟,其中2008年的模拟结果取得了0.91的效率系数,而2007年2次个例由于偏高的降水,使得洪峰流量较观测有偏大,但与观测的时间相关系数高达为0.89和0.91。研究对于山区暴雨洪水的预报预警和防汛决策具有一定的参考价值。

Numeric Simulation of Torrential Rainfall and Flash-Flood in a Mountainous Basin

The summer torrential rain which frequently occurred in the mountainous area in China often leads to flash-flood disasters.This research focus on the summer mountainous torrential rain and flood simulation based upon mesoscale numeric weather model and basin scale hydrological model.We first develop a new hydrological model name XXT based upon Xin’anjiang model and TOPMODEL which dynamical connect the surface and subsurface runoff calculation through water table depth.Three torrential rain events happened in the south Shandong province in 2007 and 2008 summer are reproduced by the Weather Research & Forecasting model(WRF),Then the simulation results from WRF are used as the inputs of XXT in order to simulate the flood.The results show that WRF has the strong capability of precipitation simulation in temporal and spatial distribution which agree well with observations.The temporal series precipitation calculated by WRF are more continuous than observed series and have higner peaks and sum values.WRF also produces the reasonable surface layer soil moisture distribution and temporal series on observational sites with higher peak values.The accumulated runoff depth calculated by WRF have good response to precipitation.Finally we use the precipitation and potential evapotranspiration from WRF results as the inputs of XXT in order to validate the flood simulation after calibrate XXT with observed data.The performance of XXT is well and the model efficacy of 2008 case is as higner as 0.91 during validation.The results of two 2007 cases have higner peak values mainly due to the overestimation of precipitation,but still with good temporal correlation with observed series with the indexs of 0.89 and 0.91 respectively.These results may provide some useful information to the torrential rain and flood operational prediction and decision maker in mountainous area.