Studies of Orographic Precipitation Processes

这项研究中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的微物理演化，并改进在各种云系中解释偏振雷达特征的方法。具体目标是利用中尺度阿尔卑斯方案(MAP)的偏振雷达测量和通过观测验证实验改进微物理参数化(IMPENMENT II)结合飞机微物理数据来解决两个尚未解决的关键科学问题：1)当地形接近和攀升主要地形障碍和精细地形特征时，地形如何影响云系统内的微物理过程和降水发展？2)暖雨微物理对山区云系中的降水过程有什么作用？实现这些科学目标的基础是根据地形云系中的偏振测量对粒子类型进行定量解释。这项研究的学术价值在于它将提供关于山脉在增强降水中的作用的新理解。这项研究还将探索解释偏振雷达测量结果的新方法。虽然过去对地形云系的研究仅限于在有飞机数据或垂直指向的遥感器的情况下有机会出现的目标，但这项研究将利用四维偏振雷达的覆盖范围，能够更详细地研究微物理过程与上游和山脉上空不断演变的云结构的关系。这一结果也将适用于非地形系统，在那里微物理过程随距离的转变不是那么突然。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，因为美国和国际上未来将使用偏振雷达来测量降雨量。这项研究将直接有助于了解欧洲阿尔卑斯山和俄勒冈州喀斯喀特地区的降水过程。在这两个地区，水资源与地形降雨量密切相关。预报模型开发人员将利用这项研究的结果来评估降水参数化，并改进对山区降水的预报。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，这些事件往往会产生灾难性的洪水。这项研究还将导致对偏振雷达数据的更好解释，随着偏振雷达投入使用，产品向预报员和公众提供，这在美国和其他国家都将是重要的。

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.