The Influence of Downstream Diurnal Heating on the Descent of Flow across the Sierras
The Influence of Downstream Diurnal Heating on the Descent of Flow across the Sierras
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DOI：
10.1175/2010jamc2516.1
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发表时间：
2010-09-01
影响因子：
3
通讯作者：
Armi, Laurence
中科院分区：
文献类型：
--
作者：
Mayr, Georg J.;Armi, Laurence
2006年3月2日，利用探空仪、气象站和两架飞机的观测资料，研究了内华达州（加州）山脉上游稳定分层气团以焚风形式下降到近3公里深欧文斯山谷的可能性。虽然上游的条件几乎保持不变，但下游的强烈日间加热使山谷气团升温，使气流仅在下午晚些时候通过山口下降到谷底。越过波峰的空气的潜在温度太高，无法下降通过由山谷气团顶部的强潜在温度台阶形成的虚拟地板，其高度在一天中变化，主要是由于山谷中的昼夜加热。下降的稳定分层流和反弹的垂直速度高达8 m s（-1）的形状的下垫面地形和虚拟谷底。
The potential for a stably stratified air mass upstream of the Sierra Nevada (California) to descend as foehn into the nearly 3-km-deep Owens Valley was studied for the 2 March 2006 case with observations from sondes, weather stations, and two aircraft flights. While upstream conditions remained almost unchanged throughout the day, strong diurnal heating on the downstream side warmed the valley air mass sufficiently to permit flow through the passes to descend to the valley floor only in the late afternoon. Potential temperatures of air crossing the crest were too warm to descend past a virtual floor formed by the strong potential temperature step at the top of the valley air mass, the height of which changed throughout the day primarily due to diurnal heating in the valley. The descending stably stratified flow and its rebound with vertical velocities as high as 8 m s(-1) were shaped by the underlying topography and the virtual valley floor.