雷达测雨及临近预报在中小流域水文视角下的应用评估

Evaluation of the Application of Radar Rainfall Measurement and Nowcasting from the Hydrological Perspective of Small and Medium Basins

地面雨量站是中小流域降雨监测的主要手段,但雨量站稳定性相对较差、运维成本高、监测留有盲区,而天气雷达能够快速获得覆盖范围内的高分辨率面雨量监测数据,一定程度上能够弥补雨量站监测的不足。选取了2012年“苏拉”、 2014年“海贝思”、2016年“尼伯特”三场台风在梅溪流域引发的三场不同类型降雨过程,探究了雷达测雨及临近预报在中小流域水文预报中的应用前景。采用24 h累积雨量相对误差RE、时空两个维度均方根误差与相应维度均值的比值m-RMSE、平均绝对误差RMAE和平均偏差RMB等指标,开展基于地面雨量站的观测值评估雷达测雨以及1、2、3 h预见期的集合临近预报。结果表明:雷达测雨总体上与地面雨量站观测值较为接近,不同类型降雨的RE值均在3%左右;时空分布均匀的降雨,临近预报效果优于短历时降雨和强降雨的临近预报效果,且随着预见期的延长,时空分布均匀的降雨预报效果更稳定,短历时降雨和强降雨的预报精度下降明显。因此,高时空分辨率的雷达测雨及临近预报在中小流域水文预报中有较好的应用前景,但短历时降雨和强降雨还需进一步研究。

Ground rainfall stations are the main means of rainfall monitoring in small and medium basins, but rainfall stations have relatively poor stability, high operation and maintenance costs, and blind spots for monitoring.Weather radar can quickly obtain high-resolution areal rainfall monitoring data within the coverage area. To a certain extent, it can make up for the lack of monitoring by rainfall stations. Three different types of rainfall processes cauesd by three typhoons in the Meixi Basin in 2012, “Saola”, 2014 “Hagibis”, and “Nepartak” in 2016 are selected to explored the effects of radar rain measurement and nowcasting in the application prospects of hydrological forecasting in small and medium watersheds. The 24 h cumulative rainfall relative error RE, the ratio of the root mean square error of the two dimensions of space and time to the mean value of the corresponding dimension m-RMSE, the mean absolute error RMAE, and the mean deviation RMB are used to evaluate.Carry out radar rain measurements and ensemble nowcasting for 1 h, 2 h and 3 h forecast periods based on observations from ground rainfall stations. The results show as follows. The radar rain measurement is generally close to the observation value of the ground rainfall station, and the RE values of different types of rainfall are all around 3%. Rainfall with uniform temporal and spatial distribution has excellent nowcasting effects. For short-duration rainfall and heavy rainfall nowcasting, and with the extension of the forecast period, the effect of uniformly distributed rainfall in time and space is more stable, and the forecast accuracy of short-duration rainfall and heavy rainfall is significantly reduced. Therefore, radar rain measurement and nowcasting with high temporal and spatial resolution have good application prospects in hydrological forecasting of small and medium watersheds, but short-duration rainfall and heavy rainfall need to be further studied.