Studies of Orographic Precipitation Processes

本研究要解决的基本科学问题是利用偏振雷达特征来了解山地云系统的微物理演化，并改进各种云系统中偏振雷达特征的解释方法。具体目标是利用来自中尺度高山计划（MAP）的极化雷达测量和通过观测验证实验改进微物理参数化（改进II）结合飞机微物理数据来解决两个关键的未解决的科学问题：1)当云系统接近并上升主要地形障碍和更细尺度地形特征时，地形如何影响云系统内的微物理过程和降水发展？2)暖雨微物理在山地云系统降水过程中的作用是什么？实现这些科学目标的基础是从地形云系统的偏振测量中定量解释粒子类型。这项研究的知识价值在于它将提供关于山脉在增加降水中的作用的新认识。该研究还将探索解释极化雷达测量结果的新方法。虽然过去对地形云系统的研究仅限于飞机数据或垂直指向遥感器可用时的目标，但本研究将利用四维极化雷达覆盖，允许更详细地检查微物理过程与上游和山脉上空云结构演变的关系。该结果也将应用于非地形系统，其中微物理过程随距离的转变不那么突然。拟议研究的更广泛影响是显著的。拟议的研究与山区水资源的有效管理直接相关，因为偏振雷达将来将在美国和国际上用于测量降水。这项研究将直接有助于了解欧洲阿尔卑斯山和俄勒冈瀑布的降水过程。在这两个地区，水资源与地形降水密切相关。预测模型的开发人员将利用本研究的结果来评估降水参数化，并改进山区降水的预测。这一点很重要，因为对降水的准确预测可以减少频繁的强降水事件对经济的影响，而强降水事件往往会产生灾难性的洪水。这项研究还将有助于更好地解释极化雷达数据，这对美国和其他国家都很重要，因为极化雷达将投入使用，预报员和公众可以获得相关产品。

The fundamental scientific problem to be addressed in this research is to use polarization radar signatures to understand the microphysical evolution of mountain cloud systems, and improve methodologies for interpreting polarization radar signatures in a wide variety of cloud systems. The specific objectives are to use polarization radar measurements from the Mesoscale Alpine Programme (MAP) and the Improvement of Microphysical Parameterization through Observational Verification Experiment (IMPROVE II) in conjunction with aircraft microphysical data to address two key unresolved scientific questions: 1) How does topography affect microphysical processes and precipitation development within cloud systems as they approach and ascend major topographic barriers and finer scale topographic features? 2) What is the role of warm rain microphysics on precipitation processes in mountain cloud systems? Fundamental to achieving these scientific objectives is the quantitative interpretation of particle types from polarization measurements in orographic cloud systems. The intellectual merit of the research has its basis in the new understanding it will provide concerning the role of mountains in enhancing precipitation. The research also will explore novel ways to interpret measurements from polarization radars. While past studies of orographic cloud systems have been restricted to targets of opportunity when aircraft data or vertically pointing remote sensors were available, this study will take advantage of four dimensional polarization radar coverage, allowing examination in much finer detail of the relationship of microphysical processes to evolving cloud structures both upstream and over the mountain ranges. The results will also have application to non orographic systems where the transitions in microphysical processes with distance are not as abrupt. The broader impacts of the proposed research are significant. The proposed research has direct relevance to the effective management of water resources in mountainous regions, since polarization radars will be used in the future in the United States and internationally, to measure precipitation. The research will contribute directly toward understanding precipitation processes over the European Alps and the Oregon Cascades. In both these regions, water resources are closely tied to orographic precipitation. Forecast model developers will use the results of this research to evaluate precipitation parameterizations and improve the prediction of precipitation in mountainous regions. This is important since accurate prediction of precipitation can reduce the economic impacts of frequent heavy precipitation events that often produce catastrophic floods. The research will also lead to a better interpretation of polarization radar data, which will be important both in the United States and in other countries as polarization radars become operational and products become available to forecasters and the public.