Impact of Terrain, Land-sea Boundaries, and Urban Areas on Convective Initiation, Structure, and Evolution over the Northeast United States

地形、陆海边界和城市地区对美国东北部对流起始、结构和演化的影响

• 批准号: 0705036
• 负责人: Brian Colle
• 金额: $ 22.58万
• 依托单位: SUNY at Stony Brook
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2007
• 资助国家: 美国
• 起止时间: 2007-06-01 至 2011-11-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0705036&HistoricalAwards=false
• 关键词: Impact; Terrain; Land; sea; Boundaries

Although severe convection is not as frequent over the Northeast United States as the central U.S., it still occurs and endangers tens of millions of people. Severe convection is often difficult to forecast across the Northeast U.S., since numerous physiographic features modify it, such as the underlying terrain and land/water boundaries. For example, severe convection may be triggered locally by lee troughs to the east of the Appalachians or by sea breeze boundaries, and then interact with urban areas such as New York City (NYC), and finally may weaken at the coast when encountering the relatively cool marine layer. However, this marine influence may depend on the synoptic scale flow regime, since elevated large-scale forcing and instability above the marine layer can maintain the convection. The core objectives of the study are threefold: (1) To develop spatial climatology of the distribution of convective frequency, intensity, and initiation areas around the Northeast U.S. coast, adjacent terrain features, and urban centers; (2) To explore how the various convective systems evolve as they approach the coast and the NYC region; (3) To investigate the physical processes associated with squall lines and elevated convection approaching the coast using mesoscale observations and high resolution simulations from a few case studies.Eleven years of WSR-88D and the National Lightning Detection Network cloud-to-ground (CG) lightning data will be used to develop a convective climatology of the region. Composite lightning counts, reflectivity, vertically-integrated water (VIL), and echo tops exceeding certain thresholds will be summed on a 4-km grid over southern New England. In order to understand the convective evolution in this region, a convective-cell tracking algorithm will be utilized. Mesoscale simulations and observations near the coast will be used to explore the three dimensional flow, impact of cooler sea surface temperatures, urban characteristics, and decreased frictional drag over water on the convective evolution. Intellectual Merit - There have been relatively few formal research studies on severe convection across the Northeast U.S. The project will improve understanding of the distribution of various convective types across southern New England in relation to different large-scale and mesoscale flow patterns, as well as how convection evolves as it approaches the coast. This study will use datasets, such as WSR-88D radar to quantify the distribution and three-dimensional structures. There have been few mesoscale model studies of severe convection across the Northeast U.S., so this study will add insight into modeling these events and the physical processes associated with convective initiation and evolution in the coastal urban environment. Broader Impacts - The Northeast convective climatology and case studies will help improve forecasting of the convective events, since these results will provide forecasters with a better conceptual model of how convection evolves near the coast for different synoptic conditions and physical processes. The numerical weather prediction community will also benefit, since the numerical model will be verified for a large number of events. This research will train two graduate students in mesoscale analysis and modeling. This project also provides an opportunity for undergraduate research in Stony Brook''s undergraduate atmospheric science curriculum and the summer Research and Experience for Undergraduates. Finally, the results from this study will be incorporated into PI''s upper-level graduate class on mesoscale dynamics.

虽然美国东北部的强对流不像美国中部那样频繁，它仍在发生，并危及数千万人。美国东北部的强对流通常很难预测，因为许多地文特征改变了它，例如底层地形和陆地/水域边界。 例如，阿巴拉契亚山脉以东的背风槽或海风边界可能会在当地引发严重的对流，然后与纽约市等城市地区相互作用，最后可能会在遇到相对凉爽的海洋层时在海岸减弱。 然而，这种海洋的影响可能取决于天气尺度的流态，因为升高的大尺度强迫和海洋层上方的不稳定性可以维持对流。该研究的核心目标有三个：（1）发展美国东北部海岸周围对流频率、强度和起始区域分布的空间气候学，邻近地形特征和城市中心;（2）探索各种对流系统如何在接近海岸和纽约地区时演变;（3）利用WSR-88 D和国家闪电探测网11年的云-地观测资料和高分辨率数值模拟资料，研究了与飑线和上升对流向海岸逼近有关的物理过程。地面闪电数据将被用来发展该地区的对流气候学。 复合闪电计数，反射率，垂直积分水（VIL），并超过一定的阈值回波顶部将在南部新英格兰的4公里网格的总和。 为了了解该地区的对流演变，对流细胞跟踪算法将被利用。 中尺度模拟和沿海附近的观测将被用来探索三维流，较冷的海面温度的影响，城市的特点，并减少对对流演变的水摩擦阻力。智力价值-有相对较少的正式研究在美国东北部的强对流的项目将提高整个南部新英格兰在不同的大尺度和中尺度流模式，以及对流如何演变，因为它接近海岸的各种对流类型的分布的理解。 本研究将使用数据集，如WSR-88 D雷达，以量化的分布和三维结构。 很少有中尺度模式对美国东北部的强对流进行研究，因此，这项研究将增加对模拟这些事件以及与沿海城市环境中对流启动和演变相关的物理过程的了解。更广泛的影响-东北对流气候学和案例研究将有助于改善对流事件的预报，因为这些结果将为预报员提供一个更好的概念模型，说明对流如何在不同天气条件和物理过程下在海岸附近演变。 数值天气预报界也将受益，因为数值模型将得到大量事件的验证。 本研究将培养两名研究生进行中尺度分析和模拟。 该项目还提供了一个机会，本科研究在石溪的本科大气科学课程和夏季研究和经验的本科生。 最后，这项研究的结果将被纳入PI的上层研究生班的中尺度动力学。