Institute for Atmospheric and Climate Science, Eidgenössiche Technische Hochschule Zurich, 8092 Zurich, Switzerland.
Proc Natl Acad Sci U S A. 2012 Jul 31;109(31):12398-403. doi: 10.1073/pnas.1204330109. Epub 2012 Jul 16.
Global warming increases the occurrence probability of hot extremes, and improving the predictability of such events is thus becoming of critical importance. Hot extremes have been shown to be induced by surface moisture deficits in some regions. In this study, we assess whether such a relationship holds at the global scale. We find that wide areas of the world display a strong relationship between the number of hot days in the regions' hottest month and preceding precipitation deficits. The occurrence probability of an above-average number of hot days is over 70% after precipitation deficits in most parts of South America as well as the Iberian Peninsula and Eastern Australia, and over 60% in most of North America and Eastern Europe, while it is below 30-40% after wet conditions in these regions. Using quantile regression analyses, we show that the impact of precipitation deficits on the number of hot days is asymmetric, i.e. extreme high numbers of hot days are most strongly influenced. This relationship also applies to the 2011 extreme event in Texas. These findings suggest that effects of soil moisture-temperature coupling are geographically more widespread than commonly assumed.
全球变暖增加了极端高温事件的发生概率，因此提高对这类事件的预测能力变得至关重要。研究表明，在一些地区，极端高温是由地表水分亏缺引起的。在本研究中，我们评估了这种关系在全球范围内是否成立。我们发现，在世界上许多地区，最热月份的高温天数与之前的降水亏缺之间存在很强的关系。在南美的大部分地区、伊比利亚半岛和澳大利亚东部，降水亏缺后出现高温日数超过平均值的概率超过 70%，在北美的大部分地区和东欧，降水亏缺后出现高温日数超过平均值的概率超过 60%，而在这些地区出现湿润条件后，概率则低于 30-40%。使用分位数回归分析，我们表明降水亏缺对高温日数的影响具有不对称性，即极端高温日数受影响最大。这种关系也适用于 2011 年德克萨斯州的极端事件。这些发现表明，土壤湿度-温度耦合的影响在地理上比通常假设的更为广泛。
