Studies of Coastal Orographic Precipitation Processes

沿海地形降水过程研究

• 批准号: 1144271
• 负责人: David Kingsmill
• 金额: $ 40.05万
• 依托单位: University of Colorado at Boulder
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2012
• 资助国家: 美国
• 起止时间: 2012-03-01 至 2017-02-28
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1144271&HistoricalAwards=false
• 关键词: Studies; Coastal; Orographic; Precipitation; Processes

Orography has a profound influence on the intensity and spatial distribution of precipitation. Broadly speaking, there are two key factors in the development of orographic precipitation: the weather regime or season, which can determine the relative importance of stable versus convective precipitation and the width of the barrier, which can determine whether orographic precipitation falls on the barrier crest or its windward or lee slopes. Of course, these relatively simple concepts do not articulate many of the complexities implicit in orographic precipitation processes, such as airflow blocking and cloud microphysics. This research effort addresses some of these complexities by focusing on coastal orographic precipitation processes. Specific objectives of this research are to:1. Examine how the coastal terrain deflects impinging low-level airflow upward to force the development of orographic precipitation;2. Investigate the structure of coastal orographic feeder clouds and how it varies as a function of upslope wind speed.These objectives will be pursued by testing specific hypotheses using airborne Doppler radar and in-situ microphysics, ground-based polarimetric Doppler radar, profiling radar, balloon sounding and surface meteorology and precipitation data from the California Land-falling Jets (CALJET) and Pacific Landfalling Jets (PACJET) experiments operated along the northern California coast during the late 1990's and early 2000's.Intellectual MeritSeveral observational field experiments have been conducted over the last forty years to help clarify unresolved details about orographic precipitation processes. Most of these efforts have been focused on relatively large barriers, with half-widths exceeding 50 km and heights more than 2 km above upstream flat terrain. Smaller barriers, with half-widths and heights less than 50 km and 2 km, respectively, can also significantly influence the development of precipitation, particularly those on or near a coastline where sources of maritime moisture are unimpeded by upstream topography. In fact, precipitation in these orographic locales can lead to severe flooding that incurs hundreds of millions of dollars in property damage. Analysis of the datasets from CALJET and PACJET provides an opportunity to advance fundamental understanding of coastal orographic precipitation processes. More specifically, this research is important because it will better clarify the forcing factors that influence the distribution and intensity of precipitation along and offshore of coastal orography and it will provide constraints on the range of microphysical processes active in coastal orographic feeder clouds and how they are influenced by forcing factors.Broader ImpactsThis research project has a variety of broader impacts. More generally, the results will have societal benefit owing to the increased knowledge of coastal orographic precipitation processes. A better understanding of the processes that lead to extreme rainfall in coastal orography could help improve hydrologic forecasts of such events. Advancements in this area also have economic and environmental relevance as water quantity has a large impact on water management, agriculture, water-based recreation, water quality and protection of endangered species habitats such as salmon fisheries. More specific broader impacts associated with this project will be student participation in the research and application of the results to classroom instruction and development of exhibits for informal science education.

地形对降水的强度和空间分布有着深刻的影响。一般来说，地形降水的发展有两个关键因素：天气状况或季节，它可以决定稳定降水与对流降水的相对重要性，以及障碍物的宽度，它可以决定地形降水福尔斯是否落在障碍物顶部或其迎风坡或背风坡。当然，这些相对简单的概念并不能清楚地表达地形降水过程中隐含的许多复杂性，如气流阻塞和云微物理。这项研究工作解决了一些这些复杂性，侧重于沿海地形降水过程。本研究的具体目标是：1.研究沿海地形如何使撞击的低空气流向上偏转，以迫使地形降水的发展;调查沿海地形馈线云的结构以及它如何随上坡风速而变化。这些目标将通过使用机载多普勒雷达和现场微物理学、地基偏振多普勒雷达、剖面雷达、来自加州登陆急流（CALJET）和太平洋登陆急流（PACJET）的气球探测和地面气象学及降水数据实验操作沿着北方加州海岸在20世纪90年代末和21世纪初。知识产权几个观测现场实验已经进行了在过去的四十年来，以帮助澄清有关地形降水过程的未解决的细节。这些努力大多集中在相对较大的障碍上，半宽超过50公里，高度超过上游平坦地形2公里。半宽和高度分别小于50公里和2公里的较小障碍物也会对降水的发展产生重大影响，特别是那些位于海岸线或海岸线附近的障碍物，因为那里的海洋湿气来源不受上游地形的阻碍。事实上，这些地形地区的降水可能导致严重的洪水，造成数亿美元的财产损失。CALJET和PACJET的数据集的分析提供了一个机会，以推进沿海地形降水过程的基本理解。更具体地说，这项研究是重要的，因为它将更好地澄清的强迫因素，影响降水的分布和强度沿着和近海的沿海地形，它将提供限制的范围内的微物理过程活跃在沿海地形馈线云，以及它们是如何受到强迫factors.Broader ImpactsThis研究项目有各种更广泛的影响。更一般地说，由于增加了对沿海地形降水过程的了解，研究结果将产生社会效益。更好地了解导致沿海地形极端降雨的过程可能有助于改善此类事件的水文预报。这一领域的进展也具有经济和环境意义，因为水量对水管理、农业、水上娱乐、水质和鲑鱼渔业等濒危物种生境的保护有很大影响。与该项目相关的更具体、更广泛的影响将是学生参与研究，并将研究结果应用于课堂教学，以及为非正式科学教育开发展品。