Possible weekly variations in the thunderstorm activity

By using observation data at the Yakutsk station (East Siberia) and the superposed epoch technique it has been obtained that there is a weekly cycle in thunderstorm activity variations which can be related to the industrial activities. To estimate a degree of thunderstorm activity variations, the observation data of VLF-radionoises and electromagnetic impulses of thunderstorm nature are used. In weekly distributions of the day level of the VLF-noises and electromagnetic impulse flux in summer, when their intensity is determined by the local thunderstorm activity, there is a main maximum in the middle of the week. The night distributions of VLF-noises and impulses caused by more distant thunderstorm sources at the time are turned out to be shifted by 1 day later relative to day distributions. (C) 2004 Elsevier Ltd. All rights reserved.