HR: 1340h
AN: AE23A-1004    [Abstracts]
TI: Positive CG flashes and possible parent cloud of sprite during winter thunderstorm seasons in Japan
AU: * Kawasaki, Z I
EM: zen@comm.eng.osaka-u.ac.jp
AF: Osaka University, 2-1 Yamada-oka, Suita, Osaka, 5650871 Japan
AU: Morimoto, T
EM: morimoto@comm.eng.osaka-u.ac.jp
AF: Osaka University, 2-1 Yamada-oka, Suita, Osaka, 5650871 Japan
AU: Ushio, T
AE23A-1004 AF: Osaka Prefecture University, 1-1 Gakuen-cho, Sakai, Osaka, 5997531 Japan
AB: An electric filed change and VHF/UHF radiation associated with positive cloud-to-ground (CG) flashes during winter in Japan has been observed, and it can be noticed that the intensity of VHF/UHF radiation increases immediately after a return stroke occurrence. It is well known that VHF/UHF radiation intensity by a negative CG decreases during and after a return stroke, and the strong VHF/UHF emission after the return stroke is believed be peculiar to the positive CG. VHF/UHF radiation due to negative CG flashes is emitted from a tip of leader progression, and a lightning channel imaging is available by VHF/UHF interferometer observations. In case of a positive CG, channel imaging of a VHF/UHF interferometer is not available. To interpret the discrepancy of VHF/UHF source mapping between negative and positive CGs, a theory of _gBi-directional Leader Concept_h is introduced. That means VHF/UHF radiation associated with a negative breakdown can be observed for both positive and negative CG, and for a negative CG that is the leader progression tip, and for positive CG that is possible positive charge regions. From this aspect, the location of VHF/UHF radiation source for positive CG mapped by interferometers may be equivalent to the location of positive charge distribution inside thunderclouds. In other words we are able to see the charge distribution by the interferometer. The 3D mapping for positive CG obtained during winter thunderstorm in Japan by means of VHF/UHF interferometer frequently gives a very large volume of source distribution, and its horizontal extension occasionally exceeds ten kilometers. The most possible altitude of the distribution of VHF/UHF source location is equivalent to or slightly lower than the altitude of -10 degree Celsius. The sources are superimposed on the radar cross section, and it is noticed that sources are rather located in a stratified region instead of a convective region. Though it has been believed that the thundercloud during winter in Japan might be small size because of weak convection, our observations by VHF/UHF interferometer are against the conventional understanding. We have occasionally experienced the MCS like thunderclouds even in winter. The total amount of charge is estimated to be a few hundred Coulombs, and it is supposed that thunderclouds, which cause positive CG during winter in Japan, should be a possible parent thundercloud.
DE: 3304 Atmospheric electricity
DE: 3324 Lightning
DE: 3329 Mesoscale meteorology
DE: 3334 Middle atmosphere dynamics (0341, 0342)
SC: Atmospheric and Space Electricity [AE]
MN: Fall Meeting 2005