Troposphere-stratosphere coupling and linkages to high latitude climate variability

该奖项是根据2009年美国复苏和再投资法案（公法111-5）资助的。摘要北半球温带地区冬季气候变率的主要统计模式是横贯极帽的同号高度异常和以中纬度洋盆为中心的异号高度异常，这两种模式受到了科学界的广泛关注。研究继续证明它对气候变率的年际信号和趋势的重要性，而且它似乎与ENSO无关。这种冬季的主导模式与高纬度地区秋季的季节性积雪之间存在一定的关系。对极帽周围高度异常的分析表明，冬季主要气候模式的成因涉及平流层和对流层之间的耦合。此外，平流层-对流层耦合是由中高纬elassen - palm （EP）通量的变率引起的。这个项目将发展和扩展我们的概念，即北半球冬季变率的主要模式是由高纬度陆地大气气候系统的不同组成部分之间的相互作用产生的。该小组将通过观察分析和不同复杂性的数值模拟实验，研究边界扰动如何在局部和远程迫使这种模式。虽然季节性积雪、EP通量和极帽高度之间存在统计上显著的关系，但仍不清楚连接积雪强迫与EP通量和极帽响应的大气桥梁，它们在时间上相隔一个月或更长时间。研究的重点是跨越10月积雪推进和初冬主要EP通量脉冲的时间间隔。提出了长超前滞后的假设，并通过一系列的GCM实验来验证每个假设。此外，还提出了GCM试验来检验积雪是平流层-对流层耦合的主动驱动因素，还是一个被动的主导指标，其本身是对大气强迫或其他一些边界强迫的共同响应。

This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5).AbstractThe leading statistical mode of winter climate variability for the extratropical Northern Hemisphere, a same-signed height anomaly stretched across the polar cap and an opposite-signed anomaly centered over the respective ocean basins of the mid-latitudes, has received much attention from the science community. Research continues to demonstrate its importance to interannual signals and trends in climate variability and that it does not appear to be related to ENSO. A relationship has been demonstrated between this dominant mode in winter and seasonal snow cover at high latitudes in the fall. Analysis of height anomalies around the polar cap demonstrate that the genesis of the dominant winter climate mode involves coupling between the stratosphere and the troposphere. Moreover, stratosphere troposphere coupling is initiated by variability in the Eliassen-Palm (EP) flux at mid- to high-latitudes. This project will develop and expand our concept that the pattern associated with the dominant winter mode of variability for the Northern Hemisphere results from interactions among the different components of the land atmosphere climate system at high-latitudes. The team will investigate how the pattern can be forced, both locally and remotely, by boundary perturbations, through observational analysis and numerical modeling experiments of varying complexity. Though a statistically significant relationship can be shown between seasonal snow cover, the EP flux and polar cap heights, what remains unclear is the atmospheric bridge that connects the snow cover forcing and the EP flux and polar cap response, which are separated in time by a month or more. The emphasis of the research will be on the time interval that spans the snow cover advance in October and the major EP flux pulse during the early winter. Hypotheses are presented for the long lead-lag and a series of GCM experiments will test each hypothesis. Furthermore GCM experiments are proposed to test whether snow cover is an active driver of stratosphere-troposphere coupling or rather a passive leading indicator, itself a common response to forcing from the atmosphere or some other boundary forcing.