The Impact of Cloud-To-Ground Lightning Type on the Differences in Return Stroke Peak Current Over Land and Ocean
The Impact of Cloud-To-Ground Lightning Type on the Differences in Return Stroke Peak Current Over Land and Ocean
复制标题
云地闪电类型对陆地和海洋回击峰值电流差异的影响
作者：
K. Cummins;Jennifer G. Wilson;A. Eichenbaum
天然云地闪电在陆地和海洋上的表现不同。这些差异可能反映了风暴在海洋上发展的速度的局部变化，并可能由局部气溶胶成分的差异造成。早期的研究报道，在海洋上的负CG第一次中风的峰值电流比陆地上的大。这项工作的重点是在这种关系的差异，为第一笔，为后续中风在现有的渠道，以地面，并为后续中风创建新的地面接触。这种区别将揭示机制负责观察到的陆地：海洋的差异，并可以支持或反驳的假设，这种差异是与向下的负先导在自由空间中的传播，驱动的电场垂直剖面内和下方的云。结果表明，当补偿的检测阈值增加与陆基传感器的距离增加，估计峰值电流的分布为后续中风在现有的（预电离）渠道地面是难以区分的分布发生在内陆，近海岸，离岸，并在遥远的海洋（离岸约200公里），与中位数值范围在14.4和15.1千安之间的闪电。相反，人口的第一次中风在遥远的海洋有更高的峰值电流比那些发生在内陆（中位数值分别为23.1千安与17.3千安），当检测阈值校正。这些发现与上述场剖面假设一致，因为由于建立新通道（第一次中风）的下行先导引起的回击的峰值电流将受到云底附近电场垂直剖面的影响最大，而先前建立的通道中中风的峰值电流应远不依赖于场剖面。
Natural cloud-to-ground (CG) lightning behaves differently over land and ocean. These differences likely reflect local variations in the speed at which storms develop over ocean, and are possibly contributed to by differences in the local aerosol composition. Earlier studies have reported statistically larger peak currents for negative CG first strokes over ocean than over land. This work focuses on differences in this relationship for first strokes, for subsequent strokes in existing channels to ground, and for subsequent strokes creating new ground contacts. This distinction will shed light on the mechanism responsible for the observed land:ocean differences, and can either support or refute the hypothesis that this difference is associated with the propagation of downward negative leaders in free space, driven by the vertical profile of electric field within and below the cloud. Results show that when compensated for detection threshold increases with increasing distance from land-based sensors, the distribution of estimated peak currents for subsequent strokes in existing (pre-ionized) channels to ground was indistinguishable from distributions for lightning that occurred inland, near shore, offshore, and in the distant ocean (~200 km offshore), with median values ranging between 14.4 and 15.1 kA. Conversely, the population of first strokes over distant ocean had much higher peak currents than those that occurred inland (median values of 23.1 kA vs. 17.3 kA, respectively), when corrected for detection threshold. These findings are consistent with the field-profile hypothesis noted above since peak currents for return strokes due to downward leaders that establish new channels (first strokes) would be impacted the most by the vertical profile of electric field near the cloud base, whereas the peak current for strokes in previously-established channels should be far less dependent on the field profile.
DOI：
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发表时间：
2014
期刊：
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影响因子：
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作者：
A. Nag;M. Murphy;K. Cummins;A. Pifer;J. Cramer
通讯作者：
A. Nag;M. Murphy;K. Cummins;A. Pifer;J. Cramer