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多时间尺度GPM降水产品在长江流域的精度评估

Evaluation of GPM precipitation accuracy over Yangtze River Basin at different time scales

  • 摘要: 高时空分辨率卫星降水产品可以弥补地面观测的不足,对长江流域降水监测与水文模型有重要作用。本文以2014—2021年长江流域国家级地面气象站的降水观测数据为基准,采用均方根误差(RMSE)、相对均方根误差(RRMSE)、相关系数(CC)、相对偏差(Bias)、命中率、误报率、关键成功指数等指标对比评估全球降水观测计划(Global precipitation measurement,GPM)两种卫星降水产品(GSMaP和IMERG)的精度,分析GSMaP和IMERG中小时、日、月降水产品在长江流域的适用性,并研究其误差的季节变化。结果表明:(1) GSMaP和IMERG卫星降水产品总体误差指标量级基本一致,在月、日、小时尺度的平均RMSE分别约为40 mm、7 mm和0.9 mm,平均RRMSE分别约为0.4、2和7,平均CC分别约为0.9、0.7和0.4,两种降水产品均表现为总体高估月和日累积降水;(2) GSMaP和IMERG卫星降水产品均表现为在月尺度上的适用性优于日和小时尺度,在长江中下游的适用性优于上游;(3) GSMaP降水产品在月、日、小时尺度上的误差程度、高估程度以及命中率表现优于IMERG,而在小时降水相关性和误报率指标上IMERG性能更优。总体上,GSMaP降水产品精度优于IMERG,能较为准确地反映长江流域日和月时间尺度的降水特征。

     

    Abstract: Satellite precipitation data with high temporal and spatial resolution can effectively address the shortcomings of ground-based observations, playing a pivotal role in precipitation monitoring and hydrological modeling within the Yangtze River Basin. This study aims to evaluate the performance of two satellite precipitation products (GSMaP and IMERG) at hourly, daily and monthly time scales by a series of metrics, such as root mean square error (RMSE), relative root mean square error (RRMSE), correlation coefficient (CC), relative error (Bias), hit rate, false alarm rate, and critical success index, in comparison with ground-based observations along the Yangtze River Basin during 2014-2021. The results are as follows. (1) The overall error metrics of the two GPM satellite precipitation products are basically the same, with an average RMSE of about 40 mm, 7 mm, and 0.9 mm at the monthly, daily, and hourly scales, and an average RRMSE of about 0.4, 2, and 7, respectively. The average correlation coefficients are about 0.9, 0.7, and 0.4, respectively. Both GSMaP and IMERG show an overall overestimation of monthly and daily precipitation. (2) Both GSMaP and IMERG exhibit better performance on a monthly scale compared to daily and hourly scale. Furthermore, they perform better in the middle and lower of the Yangtze River than in the upper regions. (3) On monthly, daily, and hourly scales, GSMaP precipitation produrcts outperform IMERG in terms of errors, bias, and hit rate, while the IMERG demenstrates better correlation and false alarm rate than GSMaP on hourly scale.Overall, the GSMaP precipitation demonstrates higher accuracy than IMERG and can capture the daily and monthly precipitation characteristics in the Yangtze River basin more precisely.

     

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