Collaborative Research: Climatological and Event-Based Radar Delineation of UHI Convection for Urban Corridors Within the Southeastern U.S.

天气损失的增加在一定程度上可以归因于美国恶劣天气更为常见的地区人口密度的增加。在进行这些观测的大尺度上，恶劣天气事件的频率和强度的变化与人为引起的气候变化没有明确的联系。然而，在较小的尺度上，例如人口集中的城市地区，人为引起的天气变化更为突出。本研究考察了城市热岛如何在美国东南部的一系列城市中增强对流。该研究为美国东南部的多城市地区开发了一种基于雷达的暖季对流气候学，这是一个雷暴多发地区，在过去的二三十年里，城市人口大幅增加。研究人员将开发一种城市/农村雷达反射率气候学，以表征几个城市和农村控制区域的对流分布。在确定的暖季大气环境下，通过同时评估六个不同规模的城市和两个控制区域周围的反射率模式，将对城市周边地区与城市热岛相关的对流在何处以及以何种强度演变进行比较综合。然后，研究人员将比较和对比这些地点的城市/农村雷达反射率最大值，并将它们与雷暴危险联系起来。最后，基于雷达的细胞跟踪仪器的发展将提供对个别城市热岛增强事件的分析。该工具将根据这些事件的方向、气象环境及其相对于土地利用和海拔的演变来评估这些事件。该研究项目将首次提供城市热岛对流如何在不同规模和地形的城市中变化的地理综合。通过根据对流事件的反射率水平（风暴对恶劣天气的倾向的替代指标）对其进行分层，研究人员将开发一套观测结果，这些观测结果可以告知研究人员和从业人员城市如何增强和减轻风暴强度，改变其运动方向，并创造雷暴活动的热点。不同土地覆盖对对流风暴影响的更复杂观点有望从这项研究中出现，其中地表特性、土地利用和城市天气模式的相互作用产生了雷暴强度和相关危害的更多地理变异。城市热岛增强是了解土地覆盖对雷暴和灾害分布影响的重要组成部分。此外，考虑到在人为引起的全球变暖情景下雷暴频率的预测增加，城市雷暴可能会放大天气和灾害规划政策的经济相关性。这项研究将允许研究人员和实践者调整和部署一种方法模板，以便在城市环境中持续监测雷暴。

Increases in weather losses can, in part, be attributable to greater population densities in regions of the U.S. where severe weather is more common. At the broad scales over which these observations have been made, changes in the frequency and intensity of severe weather events are not clearly linked to human-induced climate change. At the smaller scales, however, such as urban regions where population is concentrated, human-induced modification of weather is more prominent. This investigation examines how the urban heat island augments convection among a range of cities in the southeastern U.S. The study develops a radar-based, warm-season climatology of convection for a multi-city region in the southeastern U.S., a thunderstorm-prone area that has seen substantial increases in urban population over the last two to three decades. The investigators will develop an urban/rural radar reflectivity climatology that will characterize the distribution of convection across several cities and rural control regions. By simultaneously assessing the patterns of reflectivity around six different sized cities plus two control regions under defined warm-season atmospheric environments, a comparative synthesis will be developed of where and at what intensities urban heat island-associated convection evolves over and in the periphery of cities. The investigators then will compare and contrast urban/rural radar reflectivity maximums for these locations and associate them with thunderstorm hazards. Finally, the development of a radar-based cell-tracking instrument will provide for the analysis of individual urban heat island enhanced events. This instrument will assess these events in terms of their orientation, meteorological setting, and their evolution relative to land use and elevation.This research project will provide the first geographic synthesis of how urban heat island convection varies across cities of different sizes and topography. By stratifying convective events according to their reflectivity level, which is a surrogate of a storm's propensity for severe weather, the investigators will develop a set of observations that can inform researchers and practitioners regarding how cities enhance and lessen storm intensity, redirect their motion, and create hotspots of thunderstorm activity. A more complex view of the effects of differing land cover on convective storms is expected to emerge from this study, one in which interaction of surface properties, land-use, and urban modified weather patterns yield more geographic variability in thunderstorm intensity and associated hazards. The urban heat island enhancement is an important component in basic understanding of the role of land cover on shaping the distribution of thunderstorms and hazards. Furthermore, given predicted increases in thunderstorm frequency under a scenario of human-induced global warming, urban thunderstorms may amplify the economic relevance to weather and hazard planning policy. This research will permit researchers and practitioners to tune and deploy a methodological template for continued monitoring of thunderstorms in urban settings.