多源现代降雨数据在极端暴雨研究中的适用性比较分析

Comparative evaluation of modern precipitation datasets for extreme rainfall events over the Contiguous United States

  • 摘要: 为厘清非传统多源降雨资料在极端暴雨事件监测中的适用性与相对优势,本文基于美国国家海洋和大气管理局收录的近十年(2015—2024年)25次超常极端暴雨事件,以最新水文基准驱动数据AORC为参照,评估了3类非传统现代降雨资料(雷达产品MRMS、卫星遥感产品IMERG-Final和对流允许再分析资料CONUS404)在暴雨累积雨量、降雨过程及小时降雨强度方面的估计与探测能力。结果表明,MRMS整体表现最佳,对累积雨量和小时雨量估计的相关系数均达到0.9以上,小时降雨探测的Heidke技巧评分( Heidke Skill Score, HSS)普遍高于0.8,适用于极端暴雨监测研究。IMERG-Final对小时降雨的估计能力较好,相关系数接近0.5,在多数暴雨事件中探测能力的HSS介于0.6~0.8,但对强降雨存在明显的低估偏差。CONUS404对高分位数累积雨量估计能力较强,小时降雨估计总体偏差仅为-1.4%,但受数值模拟降雨位移误差影响,小时降雨探测能力偏弱(HSS低于0.4)。研究结果可为极端暴雨监测研究的数据优选和多源数据融合提供科学依据。

     

    Abstract: This study presents a comprehensive evaluation of three modern precipitation datasets—the NOAA gauge-corrected Multi-Radar Multi-Sensor (MRMS) product, the final run of NASA’s Integrated Multi-satellite Retrievals for GPM (IMERG-Final), and the NCAR–USGS convection-permitting hydroclimate reanalysis CONUS404—based on 25 extreme rainfall events over the contiguous United States (CONUS) during 2015–2024. These storm events were selected from NOAA’s storm events database such that, for at least one accumulation period, the observed precipitation over a large area has an annual exceedance probability (AEP) of 1/500 or less. Using NOAA’s AORC, a high-resolution gridded near-surface forcing dataset for CONUS-wide hydrologic modeling, as the benchmark, we evaluate the performance of the three datasets in terms of storm-total accumulations, temporal variations of area-mean rainfall, and hourly rain rates at both regional and pixel scales. Evaluation metrics include the Pearson correlation coefficient (PCC), relative bias (RB), and root-mean-square error (RMSE) for rainfall magnitude, and probability of detection (POD), false-alarm ratio (FAR), and Heidke Skill Score (HSS) for rainfall detection. Results show that MRMS performs best overall among the three datasets. For both accumulated rainfall and hourly rain rates, its PCC values consistently exceed 0.9, indicating that MRMS can reproduce the spatial and temporal patterns of extreme rainfall events with high accuracy. Its hourly rainfall detection capability is also strong, with HSS generally above 0.8 across different storm events. These characteristics highlight the suitability of MRMS for high-resolution monitoring and research on extreme rainfall. IMERG-Final demonstrates reasonable hourly rainfall estimation, with PCC values around 0.5 relative to the AORC reference, and moderate detection skill, with HSS between 0.6 and 0.8 for most events. It can capture the general spatial and temporal patterns of many extreme rainfall events. Nevertheless, IMERG-Final exhibits noticeable magnitude-dependent biases: heavy rainfall is significantly underestimated. For example, for the 95th percentile of storm totals, IMERG-Final tends to underestimate amounts by 79.6% across all events. For hourly rainfall, it also tends to underestimate pixel-scale rain rates overall, with an RB of −12.3%. These biases indicate that IMERG-Final should be used with caution for extreme rainfall estimation and design-storm analysis, unless additional bias-correction is applied. In contrast, the convection-permitting reanalysis CONUS404 demonstrates superior performance in estimating high-percentile accumulated rainfall at the event scale. For the 95th percentile of storm-total accumulation, its PCC against AORC can reach approximately 0.96, and RB is around −40%. Its estimation of hourly rain rates shows a relatively small negative bias (≈−1.4%), suggesting that CONUS404 precipitation intensity is not strongly biased on average. However, spatial displacement errors in the simulated precipitation fields lead to pronounced discrepancies in pixel-scale comparisons: PCC between CONUS404 and AORC hourly rain rates drops to about 0.18. CONUS404 also produces excessive hours with very light precipitation, reducing its hourly rainfall detection skill (HSS often <0.4) by lowering the probability of detection and increasing the false-alarm ratio. Overall, the three datasets exhibit complementary strengths and weaknesses. Radar-based MRMS provides the most accurate depiction of extreme rainfall structure and evolution, but its limited temporal coverage makes it less suitable for long-term studies. IMERG-Final and CONUS404 extend the temporal and spatial coverage of high-resolution rainfall information, especially where ground observations are sparse, yet their estimation biases highlight the need for careful application. The results of this study provide a scientific basis for selecting suitable precipitation datasets for extreme rainfall analysis over CONUS and for designing multi-source data-fusion strategies to improve monitoring.

     

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