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深远的影响。在这个奖项下，首席调查员将研究本地山地环流随大尺度天气模式每日变化的变化方式，以及这些本地环流对大尺度气流的反馈方式。智力优势：当气流遇到山障时，可能会在山障上方形成“山波”，并可能在下游靠近地表的地方形成背风涡。这些波浪中流动模式的明显表现可能以透镜状云的形式出现。当山波破裂时，它们形成了对航空有害的晴朗空气湍流区，它们还对更大范围的大气流动施加了阻力。在全球天气和气候的模型中，全球山脉上的水流施加的阻力的累积影响太大，不容忽视；但全球模型缺乏足够的细节来根据第一原理正确计算阻力。由于需要，这种“重力波阻力”被参数化，但这些参数化的质量和精度还不是很好。以前的大多数研究已经研究了大尺度气流在时间或空间上不变的情况下的山波和背风涡的行为，然而最近PI等人也将参与研究，他们表明，在假设的水平均匀的稳态环境中产生的山波可能与在缓慢变化的环境中产生的山波非常不同，这些环境具有两天的时间波动和2000公里波长的空间变化。初步结果还表明，大尺度变化对背风涡的结构有更显著的影响。PI将彻底研究现实的大尺度时空变化对山波和背风涡的发展和随后衰减的影响。他还将研究山波与更大尺度天气模式的相互作用，以确定这种相互作用应如何在全球天气和气候模型中表现出来。更广泛的影响：该奖项将支持两名研究生的研究和专业发展。结果可能对山区的山浪、下坡风和背风涡的预报有积极的影响。背风涡旋会对山障下风城市的空气质量产生重大影响。除了改变日常污染物的扩散，李涡还可以使化学或生物制剂在紧凑的区域内循环。这项研究还应该改进用于模拟全球天气和气候的计算机模型，帮助改善这些模型中重力波阻力的表示。