The Co-Evolution of Mesoscale Airflow over Mountains and the Larger Scale Flow

山地中尺度气流与大尺度气流的协同演化

• 批准号: 0506589
• 负责人: Dale Durran
• 金额: $ 56.2万
• 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: 2005
• 资助国家: 美国
• 起止时间: 2005-07-15 至 2009-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0506589&HistoricalAwards=false
• 关键词: Co; Evolution; Mesoscale; Airflow; over

Mountains exert a profound influence on the weather and climate. Under this award, the Principal Investigator (PI) will study the way that local mountain-induced circulations change in response to the daily changes in large-scale weather patterns, and to study the way in which these local circulations feed back on the large-scale flow. Intellectual Merit:When an air stream encounters a mountain barrier, "mountain waves" may be set up above the barrier and lee vortices may form near the surface downstream. Visible manifestations of the flow patterns in these waves may appear in the form of lenticular clouds. When mountain waves break down they form regions of clear air turbulence that are hazardous to aviation, and they also exert a drag on the larger-scale atmospheric flow. The cumulative effect of the drag exerted by flow over mountains throughout the world is too large to be neglected in models of the global weather and climate; but global models lack sufficient detail to correctly calculate the drag from first principles. Out of necessity, this "gravity wave drag" is parameterized, but the quality and accuracy of these parameterizations are not well established.Most previous investigations have studied the behavior of mountain waves and lee vortices in situations where the large-scale flow did not vary in time or space, however recently the PI, and others, who will also collaborate in the research, have shown that the mountain waves produced in hypothetical horizontally-uniform steady-state environments may be very different from those that occur in slowly varying environments with temporal fluctuations on a period of two days and spatial variations with a wavelength of 2000 km. Preliminary results also suggest that large-scale variability exerts an even more dramatic effect on the structure of lee vortices. The PI will thoroughly examine the influence of realistic large-scale temporal and spatial variations on the development and subsequent decay of mountain waves and lee vortices. He will also examine the interaction of the mountain waves with the larger-scale weather pattern in order to determine how this interaction should be represented in global weather and climate models. Broader Impacts: The research and professional development of two graduate students will be supported under this award. Results may have a positive impact on the forecasting of mountain waves, downslope winds and lee vortices in mountainous regions. Lee vortices can have a major impact on air quality in cities downwind of mountain barriers. In addition to modifying the dispersion of everyday pollutants, lee vortices can recirculate chemical or biological agents over a compact region. This research should also improve computer models for the simulation of global weather and climate by helping to improve the representation of gravity wave drag in those models.

山脉对天气和气候有着深远的影响。 根据该奖项，首席研究员（PI）将研究当地山区引起的环流如何响应大规模天气模式的每日变化而变化，并研究这些当地环流反馈大规模气流的方式。 智慧：当气流遇到高山障碍物时，障碍物上方可能会产生“高山波”，而下游接近地面的地方可能会形成背风涡。 在这些波中流动模式的可见表现可能以透镜状云的形式出现。 当山波分解时，它们形成了对航空有害的晴空湍流区域，并且它们还对较大规模的大气流动施加阻力。 在全球天气和气候模型中，流经世界各地的山脉所产生的阻力的累积效应太大，不能忽略;但全球模型缺乏足够的细节，无法根据第一原理正确计算阻力。 出于必要，这种“重力波阻力”被参数化，但这些参数化的质量和准确性还没有很好地建立。大多数以前的研究都研究了大尺度流动在时间或空间上没有变化的情况下山波和背风涡的行为，然而最近PI和其他人也将合作研究，已经表明，在假设的水平均匀的稳态环境中产生的山波可能与那些发生在缓慢变化的环境中的山波有很大的不同，这些环境具有两天的时间波动和2000 km波长的空间变化。初步结果还表明，大尺度的变化对背风涡的结构产生了更显着的影响。 PI将彻底研究现实的大规模时空变化对山波和背风涡旋的发展和随后衰减的影响。 他还将研究山波与大尺度天气模式的相互作用，以确定如何在全球天气和气候模型中表示这种相互作用。 更广泛的影响：两名研究生的研究和专业发展将在此奖项下得到支持。 研究结果对山区波浪、下坡风和背风涡的预报具有积极的意义。 背风涡会对山区屏障下风向的城市空气质量产生重大影响。 除了改变日常污染物的扩散外，背风涡流还可以使化学或生物制剂在一个紧凑的区域内再循环。 这项研究还应有助于改进模拟全球天气和气候的计算机模型，改进重力波阻力在这些模型中的表现。