Comparing Evaporative Sources of Terrestrial Precipitation and Their Extremes in MERRA Using Relative Entropy
Comparing Evaporative Sources of Terrestrial Precipitation and Their Extremes in MERRA Using Relative Entropy
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DOI：
10.1175/jhm-d-13-053.1
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发表时间：
2014-02-01
影响因子：
3.8
通讯作者：
Mocko, David M.
中科院分区：
文献类型：
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作者：
Dirmeyer, Paul A.;Wei, Jiangfeng;Mocko, David M.
采用准等熵反轨迹方案对现代研究与应用回顾分析（MERRA）的输出和带校正降水的陆地重放进行估算，以估计1979-2005年期间每个无冰陆地位置提供降水的地表水分蒸发源。任何地点和时间段的蒸发源模式都是有效的二维概率分布。因此，可以使用相对熵的方法将干旱或湿润间隔等极端情况的蒸发源与相应的气候分布进行比较。在检查月度数据时，发现显著差异在干旱时期是普遍和广泛的，但在潮湿时期则不然。在更能隔离洪水和大气河流情况的候时分辨率下，北美的相对熵值通常比月时尺度大50%-400%。显著差异表明水汽输送可能是极端降水的关键因素。在蒸发源没有显著变化的地方，这意味着可能有其他局部原因导致极端事件。
A quasi-isentropic, back-trajectory scheme is applied to output from the Modern-Era Retrospective Analysis for Research and Applications (MERRA) and a land-only replay with corrected precipitation to estimate surface evaporative sources of moisture supplying precipitation over every ice-free land location for the period 1979-2005. The evaporative source patterns for any location and time period are effectively two-dimensional probability distributions. As such, the evaporative sources for extreme situations like droughts or wet intervals can be compared to the corresponding climatological distributions using the method of relative entropy. Significant differences are found to be common and widespread for droughts, but not wet periods, when monthly data are examined. At pentad temporal resolution, which is more able to isolate floods and situations of atmospheric rivers, values of relative entropy over North America are typically 50%-400% larger than at monthly time scales. Significant differences suggest that moisture transport may be a key factor in precipitation extremes. Where evaporative sources do not change significantly, it implies other local causes may underlie the extreme events.