Global Reach-level 3-hourly River Flood Reanalysis (1980-2019)
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Better understanding and quantification of river floods for very local and flashy events calls for modeling capability at fine spatial and temporal scales. However, long-term discharge records with a global coverage suitable for extreme events analysis are still lacking. Here, grounded on recent breakthroughs in global runoff hydrology, river modeling, high resolution hydrography, and climate reanalysis, we developed a 3-hourly river discharge record globally for 2.94 million river reaches during the 40-year period of 1980-2019. The underlying modeling chain consists of the VIC land surface model (0.05°, 3-hourly) that is well calibrated and bias corrected and the RAPID routing model (2.94 million river and catchment vectors), with precipitation input from MSWEP and other meteorological fields downscaled from ERA5. Flood events (above 2-year return) and their characteristics (number, spatial distribution, and seasonality) were extracted and studied. Validations against 3-hourly flow records from 6,000+ gauges in CONUS and daily records from 14,000+ gauges globally show good modeling performance across all flow ranges, good skills in reconstructing flood events (high extremes), and the benefit of (and need for) sub-daily modeling. This data record, referred as Global Reach-level Flood Reanalysis (GRFR), is publicly available at https://www.reachhydro.org/home/records/grfr.
为更深入地理解并量化局地性、突发性河流洪水事件，亟需具备精细时空尺度的洪水模拟能力。然而，目前仍缺乏适用于极端事件分析、具备全球覆盖范围的长期径流序列记录。本研究基于全球径流水文学、河流模拟、高分辨率水文地形学及气候再分析领域的近期突破，构建了1980-2019年这40年间、覆盖全球294万个河道河段的逐3小时径流序列数据集。其核心模拟链条包含经过充分率定与偏差校正的VIC陆面模型（0.05°分辨率，逐3小时输出），以及覆盖294万个河道与集水矢量的RAPID汇流模型；降水输入数据取自MSWEP，其余气象场则由ERA5数据降尺度得到。研究提取并分析了重现期超过2年的洪水事件及其相关特征，包括事件数量、空间分布与季节特征。通过美国本土（CONUS）6000余个水文测站的逐3小时流量记录，以及全球范围内14000余个水文测站的日流量记录开展验证，结果表明该模型在全流量区间均表现优异，能够准确重建极端洪水事件，同时证实了次日尺度模拟的价值与必要性。本数据集被命名为全球河段级洪水再分析数据集（Global Reach-level Flood Reanalysis, GRFR），可通过https://www.reachhydro.org/home/records/grfr公开获取。
