基于改进降水输入模块的融雪径流模拟:以拉萨河为例

降水是自然界物质循环和水循环的重要组成部分,是高寒地区径流的重要来源,水文模型中降水数据的输入精度对提高高寒地区融雪径流模拟效果具有十分重要的作用。青藏高原地区气象站点较少,站点数据无法全面反映流域内降水时空分布的真实情况,传统的融雪径流模型在地形、风向和水汽等要素对降水垂直分布的影响考虑不够全面,制约了模型在山区融雪模拟以及预测中的应用,因此有必要对模型的降水输入项进行改进,以期提高半干旱高寒地区融雪径流模拟效果。本文基于改进的遥感卫星数据校正理论,开发了适用于半干旱高寒地区的降水输入模块,将其与度日因子模型进行耦合,利用高程分带将降水组合成半网格半站点的降水输入数据驱动模型,并在拉萨河流域进行试验研究。结果表明:降水输入模块能够显著提高降水卫星反演地面降水精度,改进后的融雪模型在率定期和验证期的NSE(Nash-Sutcliffe efficiency coefficient)分别为0.741和0.770,高于原融雪模型的模拟效果,表明改进后的模型能够在流域各个分区获得较为精确的降水数值,融雪径流模拟精度比原模型精度得到提高。总之,耦合降水输入模块的融雪模型可以有效提高降水输入精度,对缺资料半干旱高寒地区融雪模拟具有重要的参考价值。

Simulation of snowmelt runoff processes based on enhanced precipitation input module: Case studies in the Lhasa River basin

Precipitation is one of the most important components of mass balance and hydrological cycle in the natural systems and it is a dominant source of snowmelt runoff in the Alpine. Precipitation is also an important input variable for the snowmelt runoff model. It is, therefore, essential and significant to improve the accuracy of the precipitation in the snowmelt model. Qinghai-Tibet plateau is gauge scarce region and the meteorological stations are scarce to meet the demand of related studies. The meteorological station data are unable to describe the spatial and temporal distribution of precipitation. The precipitation lapse rate (PLAPS) is used in SRM to obtain the precipitation data in the different zones and the factors that terrain, wind direction, and water vapor will be ignored by the method of PLAPS. It is an important way to improve the accuracy of the snowmelt model by enhancing the module for input precipitation. A module of input precipitation was developed in this study by using the modified Successive Correction method in the semi-arid and alpine region, and it was coupled into the snowmelt runoff model. The new model was utilized to simulate snowmelt runoff in the Lhasa River basin. The results showed that the accuracy of the precipitation satellite was improved by modifying the precipitation module. The Nash-Sutcliffe efficiency coefficient values of the new model were 0.741 and 0.770 in the calibration period (2001-2007) and validation period (2008-2014). The values of Nash-Sutcliffe efficiency of streamflow using the new model were higher than the values of the original model,which indicated that this paper provided an effective approach to improve the accuracy of snowmelt simulation for gauge scarce basin in the semi-arid and alpine region.