Quantification of topographic effects on predicted precipitation for typical Elbe-catchments in the Erzgebirge

埃尔茨山脉典型易北河流域地形对预测降水影响的量化

• 批准号: 5426504
• 负责人: Professor Dr. Gerd Tetzlaff
• 金额: --
• 依托单位: Institut für Meteorologie
• 依托单位国家: 德国
• 项目类别: Priority Programmes
• 财政年份: 2004
• 资助国家: 德国
• 起止时间: 2003-12-31 至 2005-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/5426504?language=en
• 关键词: Quantification; topographic; effects; predicted; precipitation

In the flood event of 2002 precipitation forecasts were rather accurate. The overall rains on the whole slope of the Erzgebirge were rather well represented. Looking at individual pixels, however, large local and temporal deviations between forecast and observed values occurred. The major flood damage occurred in the small rivers and streams. Many of these Elbe contributaries are regulated by dams. The sizes of these catchments ranges from about 5 km² to about 200 km². This means that the typical catchment area is covered by one single pixel of a meteorological forecast model. As these catchments are located on the slope of the mountain ranges their individual topography gradient will deviate from the one in the model. In particular these gradients are threedimensional. The precipitations of the August 2002 event were to a large extent topography induced. To find out which partition of catchment wide rains is topography induced the effects of the topography of 12 dam provided catchment areas will be quantified for selected precipitation events. This means to use all available catchment area related data comprising the area covering radar-data calibrated with rain gauge data, these data themselves, and furthermore, the information available from the water budget as measured by dam authorities. The deviations between the catchment precipitations and the ones of a references site will be used to find an empirical correction factor for topographic effects. The differences between the geometries of real catchment areas and forecast model geometries will be used to derive the differences in the vertical motion, a geometry factor. The empirical and the geometry factor are applied to forecast rains, compared to the observed rains and finally used to formulate a correction factor for forecast models.

在2002年的洪水事件中，降水预报相当准确。额尔齐布尔格河整个斜坡上的总体降雨量都得到了很好的体现。然而，从单个像素来看，预测值和观测值之间存在较大的局部和时间偏差。主要的洪涝灾害发生在小河流和小溪中。易北河的许多支流都是由水坝控制的。这些集水区的面积从约5平方公里到约200平方公里不等。这意味着典型的集水区被一个气象预报模型的单个像素所覆盖。由于这些集水区位于山脉的斜坡上，它们的个别地形梯度将与模型中的地形梯度偏离。特别是这些梯度是三维的。2002年8月事件的降水在很大程度上是地形引起的。为了找出流域范围内降雨的哪一分区是地形引起的，将对选定的降水事件量化12个水坝提供的流域地形的影响。这意味着使用所有可用的集水区相关数据，包括覆盖区域的雷达数据，用雨量计数据校准的数据，这些数据本身，以及大坝当局测量的水预算信息。流域降水与参考地点之间的偏差将用于寻找地形效应的经验校正因子。实际集水区的几何形状与预测模型几何形状之间的差异将用于推导垂直运动的差异，这是一个几何因素。将经验因子和几何因子应用于预测降雨，并与观测降雨量进行比较，最后用于制定预测模型的修正因子。