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较为常见的地区人口密度增加。在进行这些观测的广泛范围内，恶劣天气事件的频率和强度的变化与人类引起的气候变化没有明显的联系。然而，在较小的尺度上，如人口集中的城市地区，人为因素对天气的影响更为突出。这项调查考察了城市热岛如何增强美国东南部一系列城市之间的对流。这项研究为美国东南部的一个多城市地区开发了一种基于雷达的暖季对流气候学，该地区是雷暴多发的地区，在过去二三十年里，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，该气候学将表征对流在几个城市和农村控制区的分布。通过同时评估在确定的暖季大气环境下六个不同规模的城市和两个控制区周围的反射率模式，将形成与城市热岛相关的对流在城市上空和城市外围演变的位置和强度的比较综合。然后，研究人员将对这些地区的城市/农村雷达反射率最大值进行比较，并将它们与雷暴危险联系起来。最后，开发一种以雷达为基础的细胞跟踪仪器将提供对个别城市热岛增强事件的分析。该仪器将根据它们的方位、气象环境以及它们相对于土地利用和海拔的演变来评估这些事件。这项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之间变化的地理综合。通过根据对流事件的反射率水平(这是风暴对恶劣天气的倾向的替代)对对流事件进行分层，调查人员将开发一套观测结果，可以向研究人员和从业者提供关于城市如何增强和降低风暴强度、改变其运动方向以及创造雷暴活动热点的信息。这项研究预计将对不同土地覆盖对对流风暴的影响产生更复杂的看法，其中地面特性、土地利用和城市修改的天气模式的相互作用导致雷暴强度和相关危险的地理变异性更大。城市热岛增强是基本理解土地复盖在形成雷暴和灾害分布方面的作用的重要组成部分。此外，考虑到在人为导致全球变暖的情况下雷暴频率预计会增加，城市雷雨可能会放大与天气和灾害规划政策的经济相关性。这项研究将使研究人员和实践者能够调整和部署持续监测城市雷暴的方法模板。

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.