Projection of extreme rainfall under climate change remains an area of considerable uncertainty. In the absence of geographically consistent simulations of extreme rainfall for the future, alternatives relying on physical relationships between a warmer atmosphere and its moisture carrying capacity are projected, scaling with a known atmospheric covariate. The most common atmospheric covariate adopted is surface air temperature, as it exhibits great consistency across climate model simulations into the future and, as per the Clausius-Clapeyron relationship, has a well-established link to atmospheric moisture capacity. However, empirical assessments of this relationship show that it varies with latitude, surface temperature, atmospheric temperature, and other factors, suggesting there may be more stable “global” atmospheric covariates that could be used instead. We argue that a better-suited covariate would be one that captures the relationship between extreme rainfall and temperature but exhibits greater consistency in the relationship across regions as well as climatic zones. Our analysis identifies plausible atmospheric indicators of changes to future extreme rainfall, which now proliferate literature and compare their suitability based on the variability they exhibit across multiple geographical, topographic, and climatic zones within Australia. It is shown that surface air temperature exhibits a regionally inconsistent relationship with extreme rainfall and hence is not suitable for projecting to future conditions. The study identified integrated water vapor and surface dew point temperature as promising alternatives, with the former showing greater consistency in space but at the cost of reduced temporal coverage.

中文翻译：

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预测未来极端降雨的改进协变量？

气候变化下的极端降雨预测仍然是一个相当不确定的领域。在缺乏地理上一致的未来极端降雨模拟的情况下，预测依赖于温暖大气与其水分承载能力之间的物理关系的替代方案，并与已知的大气协变量进行缩放。采用的最常见的大气协变量是地表气温，因为它在未来的气候模型模拟中表现出很大的一致性，并且根据克劳修斯-克拉珀龙关系，它与大气水分容量有明确的联系。然而，对这种关系的经验评估表明，它会随着纬度、地表温度、大气温度和其他因素而变化，表明可能有更稳定的“全球”大气协变量可以替代。我们认为，更适合的协变量将是捕捉极端降雨和温度之间关系的协变量，但在跨地区和气候带的关系中表现出更大的一致性。我们的分析确定了未来极端降雨变化的合理大气指标，这些指标现在激增，并根据它们在澳大利亚多个地理、地形和气候带中表现出的可变性来比较它们的适用性。结果表明，地表气温与极端降雨存在区域不一致的关系，因此不适合预测未来的情况。