Global warming has increased intensity of extreme precipitation events, and it is expected that the intensity of resulting floods will also rise, especially as intensified short-duration extreme precipitation may exacerbate dangerous flash floods. However, quantitative evidence remains limited, and existing research tends to focus on large river basins. Here we analyzed and compared how hourly extreme precipitation and streamflow in the Yangtze River Basin and its tributaries respond to temperature changes using scaling analysis. Our findings reveal a consistent temperature response across different spatial scales in the basins: hourly extreme precipitation increases at approximately 1.75 times the rate of daily precipitation. Furthermore, floods show a positive response to rising temperatures, but the degree of this response is more consistent in the mainstem than it is in the tributaries. Both daily and hourly extreme streamflow in the mainstem increases by about 7 % (7.47 % and 6.18 % respectively) for every 1 °C increase in temperature. Notably, the increase in hourly extreme streamflow is less pronounced than that in hourly precipitation intensity, likely moderated by reservoirs and the various factors influencing flood formation. In contrast, hourly extreme streamflow in most tributaries increases by 14 % or more. These findings highlight that hourly extreme precipitation and flood responses in smaller watersheds significantly exceed thermodynamic expectations, increasing flash flood risks and posing challenges for flood mitigation.

中文翻译：

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随着气温升高，每小时和小流域洪水加剧


全球变暖增加了极端降水事件的强度，预计由此产生的洪水的强度也将增加，特别是因为增强的短期极端降水可能会加剧危险的山洪暴发。然而，定量证据仍然有限，现有研究往往集中在大型河流流域。在这里，我们使用尺度分析分析和比较了长江流域及其支流每小时极端降水和径流如何响应温度变化。我们的研究结果揭示了流域不同空间尺度上的一致温度响应：每小时极端降水的增加速度约为日降水速率的 1.75 倍。此外，洪水对温度上升表现出积极的反应，但这种反应的程度在主干中比在支流中更一致。温度每升高 1 °C，主干的日和每小时极端径流量都会增加约 7%（分别为 7.47 % 和 6.18 %）。值得注意的是，每小时极端径流的增加不如每小时降水强度的增加那么明显，这可能是由水库和影响洪水形成的各种因素调节的。相比之下，大多数支流的每小时极端径流量增加了 14% 或更多。这些发现强调，较小流域每小时的极端降水和洪水响应明显超出热力学预期，增加了山洪暴发风险，并对洪水减灾构成挑战。