Mesoscale Air Flow over Topography: Modeling and Observation

地形上的中尺度气流：建模和观察

• 批准号: 9817728
• 负责人: Dale Durran
• 金额: $ 46.01万
• 依托单位: University of Washington
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 1999
• 资助国家: 美国
• 起止时间: 1999-05-15 至 2002-10-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=9817728&HistoricalAwards=false
• 关键词: Mesoscale; Air; Flow; over; Topography

Mountains exert a profound influence on the earth's weather and climate. This research will investigate two of the most important terrain-induced atmospheric phenomena: strong surface winds and gravity-wave drag.Strong surface winds may be can be generated by the interaction of the synoptic-scale flow with topography through two different mechanisms, gap winds and downslope winds. Gap winds are produced when air is forced through a narrow break in a mountain barrier. Downslope winds may be generated when air flows across mountain ridges with steep lee slopes. Significant weather hazards and extensive property damage can occur during extreme gap-wind and downslope-wind events. This study of strong oro-graphically-forced surface winds will focus on gap winds, and on the relation and interaction between gap winds and downslope winds Part of the proposed research on gap winds will involve participation the Mesoscale Alpine Programme (MAP).Gravity wave drag is often produced when stably stratified air flows over a mountain barrier. Under these conditions surface-pressure perturbations develop that exert a force on the topography that tends to accelerate the mountain in the direction of the flow. An equal and opposite force is exerted by the mountain on the airstream that tends to decelerate the overlying flow. In contrast to the drag produced by surface friction, however, the decelerative forcing associated with gravity-wave generation can be exerted at elevations far above the ground. Since the gravity waves that transport the majority of the drag aloft are too small in scale to be resolved in global weather and climate models, gravity-wave-drag processes must be parameterized in these models. The quality of the weather and climate forecasts generated by global atmospheric models is sensitive to the details of this parameterization and efforts are underway to develop improved gravity-wave-drag parameterizations. The proposed research on gravity wave drag falls within one of the crucial research areas identified for study under the U.S. Weather Research Program.

山对地球的天气和气候产生了深远的影响。 这项研究将研究两种最重要的地形引起的大气现象：强烈的表面风和重力波拖动。可以通过通过两种不同的机制，间隙风和下坡风的相互作用来产生Strong的表面风。当空气在山区屏障中狭窄的突破时，会产生间隙。 当空气在山脊上流动带有陡峭的李坡时，可能会产生下坡风。 在极端的差距和下坡事件中，可能会造成严重的天气危害和广泛的财产损失。 这项针对强烈的Oro-grapher脚地面风的研究将集中在间隙风上，以及间隙风与倾斜风之间的关系和相互作用的一部分拟议的关于间隙风的研究将涉及参与中尺度高山计划（MAP）。当时，当稳定地分层的空气流在山顶上稳定分层时，通常会产生严重性波。在这些条件下，表面压力扰动会发展在地形上施加力，从而倾向于沿流动方向加速山。 气流上的山施加了平等和相反的力，倾向于减速上覆的流动。 但是，与表面摩擦产生的阻力相反，与重力波产生相关的减速强迫可以在远远高于地面的海拔高度上施加。 由于将大多数高高阻力传输的重力波的规模太小，无法在全球天气和气候模型中解析，因此在这些模型中必须将重力波过程进行参数化。 全球大气模型产生的天气和气候预测的质量对这种参数化的细节敏感，并正在努力开发改进的重力波 - 拖动参数化。 关于重力波阻力的拟议研究属于根据美国天气研究计划确定的研究的关键研究领域之一。