Mesoscale Airflow over Mountains: Wave Drag and Orographic Precipitation

山脉上空的中尺度气流：波浪阻力和地形降水

• 批准号: 1138977
• 负责人: Dale Durran
• 金额: $ 64.88万
• 依托单位: University of Washington
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2011
• 资助国家: 美国
• 起止时间: 2011-12-01 至 2016-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1138977&HistoricalAwards=false
• 关键词: Mesoscale; Airflow; over; Mountains; Wave

Mountains exert a profound influence on the weather and climate. This project will investigate two important aspects of the interaction between mountains and the atmosphere. The first effort will be to examine how the drag exerted by mountains on an air stream is distributed among different vertical levels in the atmosphere and how that drag feeds back on the larger scale flow. The second effort will examine the way that mountains enhance precipitation and dry the air downstream.Intellectual Merit:When an air stream encounters a mountain barrier, "mountain waves" may be set up above and downstream of the barrier and the low-level flow may be blocked and diverted around the flanks of the mountain. These disturbances are too small in scale to be resolved in global weather and climate models, but they produce an important drag on the large-scale flow that must be parameterized. This project will attempt to place such parameterizations on a firmer theoretical footing and also determine the large-scale responses to orographic drag through the analysis of high-resolution numerical simulations.Although the precipitation over mountains is largely driven by the episodic passage of large-scale weather systems, prototypical theoretical studies of the interactions of an isolated ridge with such systems have not yet been undertaken, due in part to the difficulty of simultaneously modeling complex large and small-scale flows. We will take advantage of advances in computing power and model architecture to investigate the nature of the synergistic interactions of the large-scale lifting and precipitation with the more localized ascent forced by the topography. Such interactions are likely to generate more intense precipitation than that produced in previous simulations of simple upslope flows. The strength and downstream distribution of the dry air in the lee will also be determined and compared to that suggested by models forced by horizontally uniform cross-mountain flows.Broader Impacts:Two graduate students will be supported under this NSF award for their research and professional development. Research results should help improve the parameterization of low-level gravity wave drag in large-scale models essential for global weather forecasting and much climate research. Orographic precipitation is a key source of water for many of the world's civilizations. By developing a better understanding of how precipitation is enhanced when large-scale weather systems pass over topography, we can provide guidance to water resource managers and hydrologists trying to maintain water supplies in the current climate and planning for the effect of possible future shifts in mid-latitude storminess.

山对天气和气候产生了深远的影响。该项目将研究山脉与大气之间相互作用的两个重要方面。首先要做的是检查山脉在空气流上施加的阻力如何分布在大气中的不同垂直级别之间，以及该阻力如何以较大规模的流动为单位。 第二次努力将研究山区增强降水量并在下游的空气干燥的方式。智能功绩：当空气流遇到山屏障时，可以将“山脉”设置在屏障的上方和下游，并且低级流动可能会阻塞并在山脉的侧面分离。这些干扰的规模太小，无法在全球天气和气候模型中解决，但是它们会对必须进行参数化的大规模流动产生重要的阻力。 该项目将尝试将这种参数化在更牢固的理论基础上，并通过分析高分辨率数值模拟的分析来确定对地形拖延的大规模响应。尽管山上的降水在很大程度上是由大型天气系统的情节驱动的，而不是在此类系统的互动中进行的，而不是隔离途中的互动，而不是隔离途中的互动。对复杂的大型和小规模流进行建模。我们将利用计算能力和模型架构的进步来研究大规模提升和降水的协同相互作用的性质，并与地形强迫的更本地化的上升。这种相互作用可能会产生比先前对简单上坡流动的模拟中产生的更强烈的降水。 也将确定干燥空气在Lee中的强度和下游分布，并将其与由水平统一的跨山顶流动所建议的模型所建议的强度和比较。Broader的影响：这两名研究生将在该NSF奖中为他们的研究和专业发展提供支持。 研究结果应有助于改善对全球天气预测和大量气候研究至关重要的大规模模型中低级重力波阻力的参数化。地形降水是世界许多文明的主要水源。通过更好地了解当大规模天气系统超过地形时如何增强降水量，我们可以为水资源经理和水文学家提供指导，试图在当前气候下维持供水，并计划在中期暴风雨中可能改变未来的转变。

项目成果

Mountain Waves, Downslope Winds, and Low-Level Blocking Forced by a Midlatitude Cyclone Encountering an Isolated Ridge

中纬度气旋遇到孤立山脊所造成的山浪、下坡风和低空阻挡

• DOI: 10.1175/jas-d-16-0092.1
• 发表时间: 2017
• 期刊: Journal of the Atmospheric Sciences
• 影响因子: 3.1
• 作者: Menchaca, Maximo Q.;Durran, Dale R.
• 通讯作者: Durran, Dale R.