Several methods of nowcasting thundercloud lightning activities have been presented for the past few decades, using weather charts and/or stability index of upper air profiles. In this paper, the author indicates a new nowcasting method by using weather radar observations and several lightning detection systems. The first lightning discharge occurs about 5 minutes after the moderate echo top reaches the -20 degree of centigrade level, and the peak lightning activity occurs as several cells of strong echo descent from the -10 degree of centigrade level to the 0 degree of centigrade level, respectively. A single flash lightning discharge, ''Ippatsu-ra'' in Japanese, occurs as the cell of moderate echo descent from -20 to -10 degree of centigrade level to 0 degree of centigrade level (near sea or ground surface).
On the basis of simultaneous observations of cumulonimbi using the millimeter-wave radar, the X-band radar, and photogrammetry, initiations of isolated cumulonimbi in the Kanto region of Japan were presented. These cumulonimbi were organized by the continuous generation of turrets. The growth speeds of turrets were quite different among the life cycle of the cumulonimbus. The values of the growth rates increased through the life cycle of cumulonimbus in the cases of the multi-turret, and varied from 2 m/s to 13 m/s. The time relationship between the generation of cumulonimbus clouds and the turret development is different among the cases analyzed in the study. The turret developed forty minutes after the cloud generation in the case of 23 August 2010.
In non line-of-sight VHF radio wave observation, anomalous propagations due to ionospheric sporadic-E (Es propagation) and tropospheric duct (tropospheric ducting) have been frequently observed. They are known to cause an interference problem in the television, radio broadcasts and wireless communications, so that it is important to understand them. In order to make clear the characteristics of the anomalous propagations, we have observed over-horizon FM radio waves in VHF band for six years in Hiroshima and Aso. For analyses of large amounts of data set observed over years, it is important to classify and extract the radio waves automatically. In this paper, we show a method to classify above two anomalous propagations automatically. Procedures of the method are based on their propagation characteristics and received signal strength. Further the anomalous propagations and broadband noises are separated using dual frequency method. In order to evaluate the method, we examined the occurrence of the Es propagation and tropospheric ducting detected by the above method using the data observed from 2005 to 2010. It was found that the Es propagations were mostly observed in summer season and more frequently observed months in a year were June and July. Further, they were frequently observed from 10 to 12 and from 16 to 18 o’clock in a day. These results had the same tendency as past observations at mid-latitude. On the other hand, the tropospheric ducting was observed from night to morning time in spring and fall at Aso observatory.These results were consistent with past observations of occurrences of inversion layer in the troposphere from fall to spring. In contrast, it was confirmed that there were few tropospheric ducting in summer season while the past observations reported the inversion layer occurred. Since propagation characteristics of the FM radio waves have been clearly shown, it was confirmed that the classification method worked effectively.
Earlier measurements at Karymshino observatory (Kamchatka peninsula, Russia) indicated that there appeared electromagnetic radiation in the frequency range of ULF-ELF a few days before earthquakes (EQs). It was shown that its combined characteristics of the ratio of the field components and the dispersion of field ellipticity were most sensitive to this radiation. We have also shown its high efficiency as an EQ precursor. Here we have tried to estimate its reliability by using the data from an induction magnetometer at another observatory Moshiri in Japan. The data of five weeks in February-March 2007 were analyzed and as a result, reliable precursors were found for four most significant EQ events in the vicinity of the observatory.
Very low frequency (VLF) electric and magnetic field data recorded in DEMETER satellite corresponding to 30 nighttime passes over Indian longitudes during the period from 01 September to 09 December, 2010 are analyzed. The quick-look data show the existence of two intense electrostatic noise bands, one high frequency band between 04 and 18 kHz and other low frequency band below 01 kHz in majority of passes. The noise bands are electrostatic because no similar data are seen in the magnetic channel of the satellite. The characteristics of high frequency noise bands are similar to the lower hybrid resonance (LHR) bands observed in earlier satellite experiments. The data also show the occurrence of intense VLF noise bursts of duration two to three hours in the low latitude ionosphere which are analyzed thoroughly and found containing numerous first-hop magnetospherically reflected (MR) whistlers. There are some welldefined large dispersion whistlers also which appear to have propagated to the satellite in hybrid mode of propagation. A comparison with the ground data observed simultaneously at Agra station indicate insignificant and feeble nature of whistlers recorded on the ground suggesting that satellite whistlers propagated in nonducted mode of propagation and did not reach the ground. Various possibilities for the rare occurrence of VLF bursts are discussed.