应用CGDPA评估中国大陆地区IMERG的降水估计精度

Evaluation of the precipitation estimation accuracy of IMERG over China's Mainland with CGDPA

应用国家气象信息中心基于地面雨量计的逐日降水分析产品CGDPA (China Gauge-Based Daily Precipitation Analysis)为基准数据,采用定量和分类评分指标分析了2014年9月—2015年8月中国大陆地区全球降水观测GPM (Global Precipitation M easurement)多星集成降水产品IM ERG (Integrated M ulti-satellite Retrievals for GPM)的精度。结果表明:1) IMERG日平均降水量能够较好地反映我国降水量的空间分布特点(局部地区偏低),季节平均降水强度的空间分布与CGDPA具有较好的一致性(尤其中东部和南部)。2) IMERG与CGDPA日平均降水量的相关系数在大部分地区介于0. 2～0. 5,只有少数地区超过0. 6,局部地区甚至出现负相关。3) IM ERG在中国大陆东部的降水估计精度明显优于西部,但东部绝大部分地区IMERG日降水量比CGDPA偏低10%～30%,甚至更低。4) IMERG与CGDPA降水概率密度相差最大的是微量降雨,其次是中雨,其他降水强度则相差很小。5)各季节IMERG探测降水的准确率POD都比较低,空报率FAR则比较高,临界成功指数CSI也比较低。

In this study,the accuracies of the final products of Integrated Multi-satellite Retrievals for Global Precipitation Measurement(GPM)(IMERG),from September2014to August 2015 over China's Mainland(MLC),are evaluated through the quantitative and classification scoring methods using the China Gauge-Based Daily Precipitation Analysis(CGDPA)products,developed by the National Meteorological Information Center.The results are as follows:1)The IMERG can display the spatial distribution characteristics of the precipitation over MLC with relatively high accuracy,although the accuracy is lower than that obtained by the CGDPA over some areas.The spatial distribution of the IMERG seasonally averaged precipitation has a rather high consistency with that obtained by the CGDPA,especially over the central,eastern and southern parts of MLC.2)The correlation coefficients retrieved by the daily precipitation of the IMERG and CGDPA range between 0.2 and 0.5 over most areas of MLC,except for a small number of areas where they exceed 0.6,and are even negative over some areas.3)Although the accuracies of the IMERG over eastern part of MLC are significantly higher than those over the west,the daily precipitation estimation of the IMERG is as much as 10%-30% lower than the daily precipitation of the CGDPA over the east.4)The largest difference of the probability density between the IMERG and CGDPA is small-amount precipitation,followed by moderate rain,while the differences between the two in the other precipitation intensities are very minor.5)None of probabilities of detections(PODs)of precipitation events for the IMERG in any of the four seasons are significantly high,while the false alarm ratios(FARs)are relatively high.In addition,the critical success indexes(CSIs)are relatively low.