The relationship between the evolution of the tornadic storm and the cloud-to-ground (CG) activity was investigated on the F3 tornado event in Saroma-cho, Hokkaido on 7 November 2006. The echo system which caused tornadoes in Saroma-cho was the mesoscale convective system (MCS) having both the convective core region and the stratiform region. CG lightning was active in the decaying stage of the MCS. Most CG lightning was negative and occurred around a relatively strong echo area in the stratiform region of the MCS. The MCS had two peaks of the CG lightning activity at the developing and decaying stages. The Saroma tornado occurred at the decaying stage of the system when the concentration of CG frequency was observed.
Six initial continuing current (ICC) pulses contained in upward negative lightning were studied. We classified these ICC pulses into two types according to current pulse shapes.The type 1 ICC pulses had a short geometric mean (GM) of 10-90% risetimes of 8.9 μs, while the type 2 ICC pulses had a long GM of 10-90% risetimes of 55 μs. We found that the type 1 ICC pulses had preceding negative leaders which were connected to the channel of the existing ICC. These negative leaders caused the current increases of the ICC pulses by creating the conducting channels. The height of the space charges transferred by the fast rise ICC pulse is estimated to be about 700 m above sea level at most.
Continuous observations of mesospheric optical emissions (sprites) were performed from two optical sites, Shimizu and Chofu during the period of seven months from November 2004 to May 2005, with the target of specific winter sprites in the Hokuriku area of Japan (in the coast of Japan Sea). Two different kinds of analysis have been performed; one is based on the monthly data and the second is the case study. The correlation between the monthly percentage occurrence of different sprite types (columns, carrots and intermediate (including V-shaped sprites, co-existence of columns and carrots)) and monthly variation of the -10°C temperature height has indicated a negative value (r ~ -0.41) for columns and a high positive value (r ~ +0.69) for carrots. Further detailed analysis was performed with the height of -10°C at the time of sprite occurrence. It was found that winter sprites occur when the height of -10°C isotherm is located in a range from 1200 m to 3000 m. When the altitude is small, like 1200 - 1400 m, the dominant shape is columnar. When the height of -10°C is increased up to 1800 - 3000 m, a new situation takes place; that is, more spectacular shapes like carrots tend to be frequently observed. This point is also confirmed by analyzing the temperature at a particular height of 850 hPa. Carrots tend to occur above a threshold of temperature of 850 hPa (-7°C). We can conclude that charge height as the consequence charge separation caused by vertical temperature variation plays an essential role in determining the spatial forms of sprites. Finally, we discuss the initiation of sprites and sprite morphology, with a reference to the observed facts in this paper.
ELF/VLF sferics are recently recognized as an effective tool to study the global distribution of background lightning, huge lightning, global warming and meteorological anomalies, and so a lot of attention has been paid again to these sferics. This paper reviews nearly all of the direction finding methods so far proposed mainly in the VLF/ELF frequency range with different principles (single or multiple station measurement, observation of azimuth or time of arrival, etc.). Depending on your purpose, you can choose any one from these methods.
The question of whether earth tides trigger earthquakes has been the subject of debate for years. Recent studies, at last, have proven the significance of the earth tide effect in triggering earthquakes, and they further reported that the direction of the compressional stress at a region created by the earth tide almost coincides with that of the dominant principal pressure axes of the focal mechanisms at the region. This suggests that there might be specific positions of the Moon, Sun and Earth, known as lunar phases that create effective tidal force for earthquakes at each fault. So that, this paper examines the relationship between earthquakes and the lunar phases in some specific regions of Japan, and the significant effect of earth tide in triggering earthquakes is confirmed.