Short-duration rainfall extremes are expected to intensify with warming at around 7%/K, following the Clausius-Clapeyron (CC) relation, causing concomitant increases in flash floods. Observed hourly rainfall extremes show consistent CC-scaling with dewpoint temperature across all land regions. Here, we use two global climate reanalysis products (ERA5 and MERRA-2) to examine consistency in scaling with observations, in ungauged regions and over the oceans. We find that reanalyzes underestimate observed scaling, but ERA5 provides better estimates than MERRA-2. Scaling rates at high latitudes and midlatitudes are similar to observations, at CC, while over the tropics mixed negative- and super-CC scaling rates are seen. We show underestimation of scaling rates over the tropics is related to deficiencies in simulations of extreme rainfall over orographically complex and convection dominated regions. Importantly, both reanalyzes indicate scaling rates over the ocean are substantially higher than over land, with implications for extreme weather events originating over the ocean.

中文翻译：

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全球降雨量与露点温度的变化显示了相当大的海陆差异

根据克劳修斯-克拉珀龙 (CC) 关系，预计短期极端降雨会加剧，升温幅度约为 7%/K，导致山洪暴发随之增加。观察到的每小时极端降雨量在所有陆地区域显示出一致的 CC 标度与露点温度。在这里，我们使用两个全球气候再分析产品（ERA5 和 MERRA-2）来检查未测量区域和海洋上的观测尺度的一致性。我们发现重新分析低估了观察到的规模，但 ERA5 提供了比 MERRA-2 更好的估计。高纬度和中纬度的标度率与 CC 处的观测结果相似，而在热带地区，可以看到混合的负 CC 标度率和超 CC 标度率。我们表明，对热带地区缩放率的低估与对地形复杂和对流主导地区的极端降雨模拟的不足有关。重要的是，这两种重新分析都表明海洋上的缩放率远高于陆地上的缩放率，这对起源于海洋上空的极端天气事件有影响。