Mesoscale Airflow over Mountains: Modeling and Observational Analysis

山脉上空的中尺度气流：建模和观测分析

• 批准号: 0137335
• 负责人: Dale Durran
• 金额: $ 49.37万
• 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: 2002
• 资助国家: 美国
• 起止时间: 2002-05-01 至 2006-04-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0137335&HistoricalAwards=false
• 关键词: Mesoscale; Airflow; over; Mountains; Modeling

Mountains exert a profound influence on the weather and climate. This research is aimed at investigating two important ways in which mountain-induced circulations directly impact human activities: strong surface winds and violent low-level rotors.Strong surface winds may be generated by the interaction of the larger-scale flow with the topography through two different mechanisms, gap winds and downslope winds. Significant weather hazards and extensive property damage can occur during extreme gap-wind and downslope-wind events. Gap winds are produced when air is forced through gaps in a mountain barrier. The winds above mountain top level need not have a component perpendicular to the ridge line while the gap winds are blowing. Downslope winds, on the other hand, only occur if there is a significant cross-mountain wind component at ridge-top level. Downslope winds attain their high velocities as the flow descends from the mountain crest. In some cases there may be synergistic interactions between the gap flow through a mountain pass and downslope winds on the slopes adjacent to the pass. A goal of this research is to better understand the dynamics of gap winds, to determine those conditions under which a given large-scale flow is more suitable for the generation of gap winds or downslope winds, and to ultimately improve the forecasting of high wind events in mountainous regions.Airflow over long ridges often produces low-level vortices with horizontal axes parallel to the ridge line. These horizontal vortices, known as rotors, pose a serious hazard to commercial, military and civilian aviation. The rotor flow is often very turbulent. Some aircraft have reported undergoing extreme rolling motions (with roll angles approaching 90 degrees), and some aircraft have been lost under conditions when strong rotors were believed to have been present. Recent work by the Principal Investigator and collaborators has identified the basic source of rotation within a typical rotor. Just as the tornadoes contain embedded regions of high vorticity (suction vortices), terrain induced rotors also appear to contain localized regions of very high vorticity. At present, almost nothing is known about the maximum strength or the dynamics of these subrotors, yet they may pose the most danger to aircraft. A goal of this proposal is to develop a better understanding of the probable strength, frequency of occurrence, and the dynamics of these subrotors.Successful completion of this research can potentially lead to better forecasts of mountain-induced severe wind hazards.

山对天气和气候产生了深远的影响。 这项研究旨在调查山区诱发的循环直接影响人类活动的两种重要方法：强烈的表面风和剧烈的低级转子。通过两种不同的机制，间隙风和下坡风的相互作用，可以通过大规模流与地形的相互作用与地形相互作用产生巨大的表面风。 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。 当空气通过山区屏障的缝隙强迫空气时会产生间隙。 山顶上方的风不必具有垂直于山脊线的组成部分，而间隙风正在吹。 另一方面，下坡风只有在山脊顶水平有明显的跨山风组件时才发生。 下坡风的速度达到了高速，随着山峰的下降。 在某些情况下，缝隙流过山通道和与通行证相邻的斜坡上的下坡风之间可能存在协同的相互作用。 这项研究的一个目的是更好地了解间隙风的动态，以确定给定的大规模流动更适合生成间隙风或下坡风的条件，并最终改善对山区山脉中的高风向事件的预测。在长山脊上播放的高风通常会产生与水平轴线平行的低级涡流线。 这些水平涡流（称为转子）对商业，军事和平民航空构成了严重危害。 转子流通常非常动荡。 一些飞机报告说，发生极端的滚动运动（滚动角接近90度），并且在据信较强的转子存在的情况下，有些飞机丢失了。 首席研究员和合作者的最新工作已经确定了典型转子内的基本旋转来源。 正如龙卷风包含高涡度嵌入的区域（抽吸涡旋）一样，地形诱导的转子似乎也包含非常高的涡度局部区域。 目前，关于这些子观看器的最大强度或动态几乎一无所知，但它们可能对飞机构成最大的危险。 该提案的一个目的是更好地了解可能的强度，发生的频率和这些子活体的动态。完成这项研究的成功可能会导致更好地预测山区引起的严重风危害。