Dynamics of Heavy Precipitation over Mesoscale Mountains

中尺度山脉强降水动力学

• 批准号: 0344237
• 负责人: Gary Lackmann
• 金额: --
• 依托单位: North Carolina State University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2004
• 资助国家: 美国
• 起止时间: 2004-05-01 至 2008-04-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0344237&HistoricalAwards=false
• 关键词: Dynamics; Heavy; Precipitation; over; Mesoscale

The objective of this research is to advance scientific understanding of orographic rainfall. Three major questions will be addressed:(1) In addition to the moist Froude number, what are other major non dimensional parameters that control the propagation of orographically induced mesoscale convective systems over mountains?(2) What are the formation and propagation mechanisms of convective cells embedded in an orographic mesoscale convective system?(3) How does an upper-level jet streak couple with the low-level flow to create an environment that is highly favorable for heavy orographic precipitation?In order to address the first question, the Principal Investigator will extend previous studies to investigate other major control parameters for a conditionally unstable orographic flow. A series of idealized numerical experiments will be performed using a mesoscale numerical model to study the effects of basic flow speed, instability, moisture content, aspect ratio of the mountain, Coriolis force and vertical wind shear on moist flow regimes. In order to address the second question, the Principal Investigator hypothesizes that advection is the major mechanism for the generation of convective cells. This advection mechanism will be tested by performing a series of numerical experiments. Regarding the third question, it is hypothesized that there is a vertical coupling process between the boundary layer flow and upper-level jet streak that creates an environment that is highly favorable for heavy orographic precipitation. A mesoscale numerical model will be adopted to perform real-case numerical experiments to help answer this question. The intellectual merit of this approach is largely derived from the unique multi-faceted synthesis of idealized numerical modeling, real data numerical modeling and observational data analyses as applied to the problem of why heavy orographic rainfall occurs over mesoscale mountains.The broader impacts will be achieved by utilizing the research findings for the development of improved forecast techniques of extreme orographic rainfall predictions. It is anticipated that this will result in the saving of lives and the reduction of property losses.

这项研究的目的是促进对地形降雨的科学理解。我们将讨论三个主要问题：(1)除了湿弗劳德数之外，控制地形诱发中尺度对流系统在山区传播的其他主要无量纲参数是什么？(2)嵌入地形中尺度对流系统的对流单体的形成和传播机制是什么？(3)高空急流条纹如何与低层气流相耦合，创造出非常有利于强地形降水的环境？为了解决第一个问题，首席调查员将扩展以前的研究，以研究条件不稳定地形气流的其他主要控制参数。利用中尺度数值模式进行了一系列理想化的数值试验，研究了基本水流速度、不稳定性、含水率、山体纵横比、科里奥利力和垂直风切变对湿流态的影响。为了回答第二个问题，首席调查员假设平流是产生对流单体的主要机制。这一平流机制将通过一系列数值试验进行检验。关于第三个问题，假设边界层气流和高空急流之间存在一个垂直耦合过程，从而创造了一个非常有利于强降水的环境。为了帮助回答这个问题，将采用中尺度数值模式进行真实的数值试验。这种方法的智力优势主要来自于理想化数值模拟、真实数据数值模拟和观测数据分析的独特多方面综合，用于解决中尺度山脉上为什么会出现强地形降雨的问题。利用研究成果将获得更广泛的影响，以发展改进的极端地形降雨预报技术。预计这将导致拯救生命和减少财产损失。