多普勒天气雷达1 h降水产品的质量评估

为评估多普勒天气雷达1 h降水量(OHP)产品在降水预报中的质量, 从南通新一代多普勒天气雷达的体扫资料及其覆盖范围内太湖流域34个雨量站的同期逐小时降水资料中选取了19个降水个例。以空报率、漏报率、准确预报临界指数、平均误差、平均绝对误差和均方根误差等, 为评估降水预报质量的指标。根据雨量站实测日降水量(P)和1 h降水量(P₁)大小分级, 对不同情况下的OHP进行质量评估。结果表明:(1)OHP的空报率和漏报率较高, 导致整体的准确预报临界指数偏低。(2)与不同的P和P₁量级相对应, 不同的OHP预报质量有明显差异。除P<10 mm时和P₁<1 mm时稍有高估外, 其他量级都存在低估, 且随着P的增加, 空报率和漏报率都减小。(3)对2007年9月18日的降水个例分析表明:OHP与实测的落区基本一致, 但降水强度上有偏差。不同站点的雨强偏差不同, 距南通雷达站100 km左右的OHP误差较小。

Quality evaluation of Doppler radar product in Taihu Lake Basin

In order to evaluate the quality of Doppler radar's One Hour Precipitation (OHP) product in the precipitation forecast, 19 rainfall cases were selected from the volume scan data of the new generation Doppler radar in Nantong City and the corresponding hourly precipitation data covering 34 rain gauges in Taihu Lake Basin, moreover, False Alarm Rate (FAR), Missing Alarm Rate (MAR), Critical Success Index (CSI), Mean Error, Mean Absolute Error and Root Mean Square Error were selected as the evaluation indices of the OHP product quality. According to the grades of the daily and hourly rainfall from the observed data, the quality of OHR in different cases were evaluated. Results showed that: (1) the high FAR and MAR of radar's 1 h accumulated precipitation led to the low integral CSI . (2) The forecast quality of radar's 1 h accumulated precipitation at different rainfall rates was diversitfied obviously corresponding to the different daily and hourly rainfall derived from the observed data. The underestimation was common event except for the daily and hourly rainfall below 10 mm and 1 mm. The FAR and MAR decrease with the daily rainfall increasing. (3) The analysis on a rainfall case on September 18, 2007 indicated that the radar's 1 h accumulated rainfall area was consistent with the actual rainfall area, but in the case of precipitation intensity a certain of deviation was evident. The deviation of each gauge was different, and the errors of gauges about 100 km from Nantong radar station were the least.