The Lighting Flash
Early studies of lightning relied heavily on photographic and electric field measurements. Consequently, a lightning flash was defined in terms of these observations. The whole alphabet soup of lightning components (C, J, K, M, R changes, etc.) was defined from photographic and electric field measurements. The convenient, well-boxed concept of “the flash was defined during the pioneering studies of investigators such as Brook and Kitagawa. Today, we enjoy powerful, remote sensing tools that enable us to peer deep inside thunderclouds and study lightning as it develops. These instruments greatly expand out ability to study thunderstorms and lightning, but they also complicate our ability to quantize lightning activity into a flash. The Optical Transient Detector (OTD) and Lighting Imaging Sensor (LIS) have provided detailed, global measurements of lighting activity. They detect discrete optical pulses produced by lightning. These pulses are typically associated with the more energetic processes of a lightning flash such as return strokes and K-changes. Whereas electric field change measurements provide a scalar, time continuous sequence of events that are readily assigned as a flash, the pluses detected by LIS and OTD are discrete and are assigned as members of a specific flash through a somewhat arbitrary time-space association. With these instruments which have large fields of view that often contain many thunderstorm cells, the assignment of discrete optical pulses to a specific flash can be somewhat random. The same problem exists with lightning mapping arrays (LMA) where it can sometimes be difficult to determine which piece of channel to assign to what flash. Like the LIS/OTD, a LMA flash is defined by a time–space grouping of VHF pluses. The measured flash rate of a given storm can vary significantly depending on the grouping algorithm. In this presentation, simultaneous electric field change, LIS and LMA are analyzed in order to better understand the lightning flash.
H. J. Christian J. Latham M. G. Bateman
NSSTC, University of Alabama in Huntsville, 320 Sparkman Drive, Huntsville, AL 35899, USA NCAR, P.O.Box 3000, Boulder, CO 80301, USA Universities Space Research Association, Huntsville, AL, 35805, U.S.A
国际会议
第13届国际大气电学会议(The 13th International Conference on Atmospheric Electricity)
北京
英文
2007-08-13（万方平台首次上网日期，不代表论文的发表时间）