Collaborative Research: Investigating the Thunderstorm Climatology of a Rapidly Urbanizing Arid Region, the Las Vegas Valley, Nevada

在北美的湿润和干旱地区，城市对行星边界层中的热条件的改变都有很好的记录。这些变化的表现之一是城市热岛。在美国东南部等潮湿地区，也已经建立了对城市及其周围地区对流调节过程的城市改造。在干旱地区，人们对城市化与区域对流参数变化之间的关系知之甚少。这一合作研究项目将检查与内华达州干旱的拉斯维加斯山谷对流有关的参数的修改。拉斯维加斯山谷在过去30年里一直在快速城市化，并在夏季产生了广泛的城市热岛。研究人员首先将按照干旱地区建立的程序，如亚利桑那州凤凰城制定的程序，分析1990年至2006年期间城市热岛的强度和范围。然后，该项目的目标将转向收集、格式化和整合地面、高空和遥感气象数据集。数据整合程序将根据时间和空间分辨率配对数据集，并为点数据集制定适当的内插程序，以便在一个共同的网格结构内解释这些数据。要整合的数据来源包括克拉克县区域防洪控制区地面中尺度网络观测(温度、风速/风向和降雨量)、NEXRAD体积扫描(综合反射率、风暴相对速度和降雨率)、国家闪电探测网络(NLDN)点数据(云对地闪电)、地球同步业务环境卫星(GOES)图像(可见光和热红外)和区域无线电探空观测(RAOB)网络探测(热力学参数)。在数据整合阶段之后，研究人员将测试一些方法，以确定提取与拉斯维加斯辐合区(LVCZ)的强度、持续时间和位置以及北美季风(NAM)环流的强度、持续时间和范围有关的信息的最有效技术。在前一研究阶段开发的综合数据集将用于敏感性研究，以测试在存在强/弱低层气旋情景以及在强和弱NAM环流期间探测城市热岛对流影响信号的可行性。这项概念验证研究的主要目标是汇编一些案例研究，说明拉斯维加斯河谷夏季对流期间多尺度大气过程的空间和时间相互作用。案例研究将包括描述对流云发展、CG闪电和山谷对流降雨的参数。该项目将设计实验和进行案例研究，以评估确定可测量的城市热岛对美国干旱西南部城市地区夏季对流的影响的可行性。该项目将分析中尺度和天气尺度环流，如拉斯维加斯辐合区(LVCZ)和北美季风(NAM)，这些环流如何在拉斯维加斯山谷产生复杂和相互关联的对流环境。它还将产生案例研究，说明这两个过程中的可变性。描述对流云的区域发展、云对地闪电和降雨模式的参数将被包括在对弱和强NAM环流以及弱和强低层气旋发展的案例研究中。这项研究将在内华达大学的研究生和内华达州里诺市莫洛高中的高三实习生的帮助下进行，这是之前建立的学生实习计划的一部分。这项研究产生的案例研究将提供给内华达州的地理联盟，作为课程改进项目的一部分，分发给全州的科学教师。该项目将促进对干旱地区城市气候学的基础科学理解。它将提供关于北美季风对中尺度过程的影响的新见解，以及在对流研究中使用云对地闪电数据。该项目还将为拉斯维加斯山谷的规划界提供数据集和案例研究，为与防洪、公共安全和住宅开发相关的决策提供背景。

Urban modification of thermal conditions in the planetary boundary layer has been well documented in both humid and arid regions of North America. Among the manifestations of these modifications is the urban heat island. Urban modification of processes modulating convection in and around urban areas also has been established in humid regions like the southeastern U.S. The relationship between urbanization and changes in regional convective parameters is less well understood in arid regions. This collaborative research project will examine modification of parameters related to convection in the arid Las Vegas Valley of Nevada. The Las Vegas Valley has been rapidly urbanizing over the past three decades and produces an extensive urban heat island during the summer season. The investigators initially will analyze the intensity and extent of the urban heat island for the period from 1990 to 2006 following procedures established in arid regions, such as those developed in Phoenix, Arizona. The objective of the project then will shift to collecting, formatting, and integrating surface, upper-air, and remotely sensed meteorological data sets. The data-integration procedure will pair data sets based on temporal and spatial resolution and develop appropriate interpolation procedures for point data sets so that these data can be interpreted within a common grid structure. Sources of data to be integrated include the Clark County Regional Flood Control District surface meso-network observations (temperature, wind speed/direction, and rainfall), NEXRAD volume scans (composite reflectivity, storm-relative velocity, and rainfall rate), National Lightning Detection Network (NLDN) point data (cloud-to-ground lightning flashes), Geostationary Operational Environmental Satellite (GOES) imagery (visible and thermal infrared), and regional radiosonde observation (RAOB) network soundings (thermodynamic parameters). Following the data-integration phase, the investigators will test a number of methodologies to identify the most efficient techniques for extracting information related to the intensity, duration, and location of the Las Vegas Convergence Zone (LVCZ) and the intensity, duration, and extent of the North American Monsoon (NAM) circulation. The integrated data set developed in the prior research phase will be used in sensitivity studies to test the feasibility of detecting a urban heat island impact signal on convection in the presence of strong/weak LVCZ scenarios and during strong and weak NAM circulations. A primary objective of this proof-of-concept study will be the compilation of a number of case-studies that illustrate the spatial and temporal interactions of multi-scale atmospheric processes during summer season convection episodes in the Las Vegas Valley. The case studies will include parameters describing convective cloud development, CG lightning flashes, and convective rainfall in the valley.This project will design experiments and conduct case studies to assess the feasibility of identifying a measurable urban heat island influence on summer season convection in an urban region in the arid southwestern U.S. The project will analyze meso-scale and synoptic scale circulations like as the Las Vegas Convergence Zone (LVCZ) and the North American Monsoon (NAM), how those circulations can produce a complicated and interrelated convective environment in the Las Vegas Valley. It also will yield case studies illustrating variability in both processes. Parameters describing regional development of convective clouds, cloud-to-ground lightning flashes, and rainfall patterns will be include in case studies for weak and strong NAM circulations and for weak and strong LVCZ development. The research will be carried out with the assistance of graduate students from the University of Nevada and with high school senior interns from Monogue High School in Reno, Nevada as part of a previously established student internship program. The case studies produced by the research will be made available to the Geographic Alliance in Nevada, for distribution to science teachers statewide as part of a curriculum enhancement project. This project will advance fundamental scientific understanding in urban climatology in arid regions. It will provide new insights regarding North American Monsoon influence on meso-scale processes, and the use of cloud-to-ground lightning flash data in the study of convection. The project also will provide the planning community in the Las Vegas Valley with data sets and case-studies that provide context for decisions related to flood control, public safety, and residential development.