Physical and Meteorological Characteristics Associated with Lightning Ground Flashes: The National Lightning Detection Network and the Canadian Lightning Detection Network

这笔拨款支持使用国家闪电探测网络（NLDN）的数据继续分析美国各地的闪电和闪电特征。这些数据可以追溯到1983年。除了美国的数据外，还将增加加拿大闪电探测网络（CLDN）的数据，该网络成立于1997年。这两个网络总共包含187个传感器，提供的数据范围从北纬25度到60度，从西经50度到135度。这些网络上记录的闪光次数超过3亿次。这些数据用于表征云对地闪电的不同特性，包括闪光极性、每单位面积的闪光次数、峰值电流和冲程多重性。目前正在研究这些数量随季节和地理位置的变化，以及它们对诸如山脉和城市等地方特征的依赖。已经有证据表明，城市地区的闪电率增加，这可能是由于高温城市上空对流增加或污染气溶胶的微物理效应造成的。到目前为止的其他发现是，最高的峰值电流在中西部北部，而最高比例的正向闪光是在美国西海岸。对这些发现的物理解释将作为项目的一部分进行探索。

This grant supports a continuation of the analysis of lightning flash and stroke characteristics across the United States using data from the National Lightning Detection Network (NLDN). These data extend back to 1983. To the American data will be added data from the Canadian Lightning Detection Network (CLDN), which was established in 1997. The two networks combined comprise 187 sensors and provide data extending from 25 degrees to 60 degrees N latitude and from 50 degrees to 135 degrees W longitude. The number of recorded flashes on these networks exceeds 300 million. The data are used for characterizing different properties of cloud-to-ground lightning, including flash polarity, the number of flashes per unit area, the peak current, and stroke multiplicity. Studies are under way on the variation of these quantities with season and geographical location, and their dependence on local features such as mountains and cities. There is already evidence of increased flash rates over urban areas, explained perhaps by increased convection over heated cities or by microphysical effects of pollution aerosols. Other findings to now are that the highest peak currents are in the upper Midwest and the highest percentage of positive flashes to ground are along the West Coast of the United States. Physical explanations for these findings will be sought as part of the project.