Interactions Between the Nighttime Valley-Wind System and a Developing Cold-Air Pool
详细信息 查看全文
- 作者：Gabriele Arduini ; Chantal Staquet ; Charles Chemel
- 关键词：Cold ; air pool ; Downslope flow ; Numerical simulation
- 刊名：Boundary-Layer Meteorology
- 出版年：2016
- 出版时间：October 2016
- 年：2016
- 卷：161
- 期：1
- 页码：49-72
- 全文大小：2,403 KB
- 刊物类别：Earth and Environmental Science
- 刊物主题：Earth sciences
Meteorology and Climatology
Atmospheric Protection, Air Quality Control and Air Pollution - 出版者：Springer Netherlands
- ISSN：1573-1472
- 卷排序：161
文摘
The Weather Research and Forecast numerical model is used to characterize the influence of a thermally-driven down-valley flow on a developing cold-air pool in an idealized alpine valley decoupled from the atmosphere above. Results for a three-dimensional (3D) valley, which allows for the formation of a down-valley flow, and for a two-dimensional (2D) valley, where the formation of a down-valley flow is inhibited, are analyzed and compared. A key result is that advection leads to a net cooling in the 2D valley and to a warming in the 3D valley, once the down-valley flow is fully developed. This difference stems from the suppression of the slope-flow induced upward motions over the valley centre in the 3D valley. As a result, the downslope flows develop a cross-valley circulation within the cold-air pool, the growth of the cold-air pool is reduced and the valley atmosphere is generally warmer than in the 2D valley. A quasi-steady state is reached for which the divergence of the down-valley flow along the valley is balanced by the convergence of the downslope flows at the top of the cold-air pool, with no net contribution of subsiding motions far from the slope layer. More precisely, the inflow of air at the top of the cold-air pool is found to be driven by an interplay between the return flow from the plain region and subsidence over the plateaux. Finally, the mechanisms that control the structure of the cold-air pool and its evolution are found to be independent of the valley length as soon as the quasi-steady state is reached and the down-valley flow is fully developed.