Temperature influences on intense UK hourly precipitation and dependency on large-scale circulation
Temperature influences on intense UK hourly precipitation and dependency on large-scale circulation
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DOI：
10.1088/1748-9326/10/5/054021
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发表时间：
2015-05-01
影响因子：
6.7
通讯作者：
Fowler, H. J.
中科院分区：
文献类型：
--
作者：
Blenkinsop, S.;Chan, S. C.;Fowler, H. J.
短时间的强降雨可能会对社会产生重大影响，特别是城市洪水。气候模型预测表明，在气候变化的情况下，降水将加剧。这与根据热力学克劳修斯-克拉皮隆(CC)关系(速率类似于摄氏6-7度)--较暖的大气能够容纳更多水分--降水强度将随着温度增加而增加的假设一致。因此，温度和极端降水之间的CC标度在许多研究中和在不同的地点被证明，在次日极端事件中观察到的CC标度(所谓的超级CC标度)高于CC标度。在这里，我们使用一个新的英国每小时降水数据集来确定平均日气温和第99百分位每小时降水强度之间的季节性比例关系。汇集整个英国的数据表明，在气温较高的春季和夏季，CC标度仅略高于CC标度，显著低于其他地区观察到的2xCC标度。在英国，最高的小时强度和最高的尺度都出现在夏季，因此，对于这个季节，尺度关系对大尺度环流条件的依赖性被用一组气流指数来检验。切变涡度指数(指示大尺度气流气旋性)对这种关系的影响最大，当切变涡度为负(反气旋旋转)时，在较高的温度下接近2xCC。对强烈事件发生的考察表明，这些事件可以在气旋和反气旋条件下发生，但在英格兰东南部，后一种条件更有利于它们的发生。这些结果表明，环流机制的变化可能会改变CC尺度规定的降水强度的预期变化，并因未来变暖而产生。
Short periods of intense rainfall may be associated with significant impacts on society, particularly urban flooding. Climate model projections have suggested an intensification of precipitation under scenarios of climate change. This is in accordance with the hypothesis that precipitation intensities will increase with temperature according to the thermodynamic Clausius-Clapyeron (CC) relation (a rate of similar to 6-7%degrees C-1)-a warmer atmosphere being capable of holding more moisture. Consequently, CC scaling between temperature and extreme precipitation has been demonstrated in numerous studies and in different locations, with higher than CC scaling (so-called super CC scaling) observed for sub-daily extremes. Here we use a new dataset of UK hourly precipitation to identify seasonal scaling relationships between mean daily temperature and 99th percentile hourly precipitation intensities. Pooling the data for the whole UK indicates only slightly higher than CC scaling in spring and summer at higher temperatures, notably less than the 2xCC scaling observed in other regions. Both the highest hourly intensities and the highest scaling in the UK occur in summer and so for this season the dependency of the scaling relationship on large scale circulation conditions is examined using a set of air flow indices. A shear vorticity index (indicative of large-scale flow cyclonicity) is noted to have the greatest influence on the relationship, approaching 2xCC at higher temperatures when shear vorticity is negative (anticyclonic rotation). An examination of the occurrence of intense events indicates that these can occur under cyclonic and anticyclonic conditions but that in the southeast of England the latter conditions disproportionately favour their occurrence. These results suggest that changes in circulation regimes could modify the expected changes in precipitation intensities prescribed by CC scaling and arising as a consequence of future warming.