Characteristics of the Sprite Parent Winter Thundercloud with Positive Single Flash in Hokuriku, Japan (A Case Study on 14th December 2001)

Abstract

The sprite campaign was conducted by the sprite research group of University of Electro-Communications (UEC) during the winter of 2001/2002. On 14th December 2001, nine sprites were observed from Shimizu in Shizuoka and ELF transients were measured at Moshiri in Hokkaido. One of the sprites was also observed by the weather radar and the field mill network around the Komatsu Air Base. The sprite parent thunderclouds associated with the positive cloud-to-ground flash (+CG) were investigated with special reference to their electrical and meteorological characteristics. The results are summarized as follows; ( ) The sprite parent thundercloud was very small (horizontal scale is at most 30 km) and the sprite was generated by a single flash when the thunderclouds were dissipating just after the maximum activity. ( ) The sprite parent +CG occurred under the stratiform region of the thunderclouds. ( ) Before the sprite causative +CG occurred, very large positive charge and negative one were found in and over the thundercloud by the analysis of sequential field mill observation.

Meteorological and electrical aspects of several winter thunderstorms with sprites in the Hokuriku area of Japan

“… Williams and Yair [2006] have described that winter thunderstorms in the Hokuriku region are still considered to be larger than ordinary summer isolated thunderstorms. Suzuki et al [2006a, 2006b] also pointed out that the winter thunderstorm echo is much smaller than the summer MCSs, although winter thunderstorms have a very large cloud area equivalent to MCSs, and a sprite‐causative positive charge reservoir tended to reside in the cloud area (anvil‐like stratiform cloud). Winter sprite parent thunderstorms would not strictly correspond to the definition of MCSs provided by Mohr and Zipser [1996], even if the cloud area were very large, because an MCS is defined on the basis of the extent of the radar reflectivity area (>2000 km 2 ).…”

“…The frame integration time was 33.3 ms, and the accuracy of the time of the event was ±16.7 ms. An accurate azimuth of CCD cameras was determined by using the star field in the video frames, and sprite elements in the video frame were localized by triangulation with two CCD cameras. Second, the operating SAFIR lightning detection system in the Hokuriku region consists of three VHF/LF sensors with a short base line of several tens of kilometers as indicated in the upper left inset as stars [ Suzuki et al , 2006a, 2006b]. Each sensor detects the direction of the VHF lightning radiation source associated with either IC or CG by interferometry.…”

“…The first winter sprites were observed there in 1998 [ Fukunishi et al , 1999], a decade after the first imaging of summer continental sprites [ Franz et al , 1990]. Since then, Japanese winter sprite campaigns have been conducted extensively using various instruments (high‐sensitivity CCD camera, C‐band radar, two‐dimensional (2‐D) cloud‐to‐ground lightning mapping system, and meteorological satellite) [ Hobara et al , 2001, 2006; Takahashi et al , 2003; Hayakawa et al , 2004; Suzuki et al , 2006a, 2006b].…”

“…Their results suggested that winter sprite parent thunderstorms are usually lower and smaller than MCSs in the U.S. High Plains. It is additionally found that the parent thunderstorms, including active radar echo cells, are also very small (cell size is about several tens of kilometers) [ Hayakawa et al , 2004, 2005, 2007; Suzuki et al , 2006a, 2006b]. On the basis of the analysis of four different winter storms with sprites above the eastern Mediterranean, Ganot et al [2007] have concluded that the areas of active convective part were 6000∼30,000 km 2 , and their average vertical extents were from 5 to 7 km, reaching a cloud top height of 8∼9 km (T ∼ –40°C).…”