Characteristics of thunderstorm systems producing winter sprites in Japan

Abstract

In this work, we analyze 67 sprite events observed during the winter sprite campaign carried out in Japan from 1998 to 2003. Our aim is to clarify the relationship between winter sprites in Japan and the characteristics of their parent thunderstorm systems. Combining optical data of sprites, various meteorological data such as cloud maps obtained from the Geostationary Meteorological Satellite-5, and precipitation maps obtained from Doppler radars as well as lightning detection network data, we classify sprite-producing thunderstorm systems into four categories: (1) those associated with the cold front over the Sea of Japan, (2) those developing in the Japan Sea Polar Air Mass Convergence Zone, (3) those developing in local low-pressure areas over the Pacific Ocean, and (4) those developing ∼200-900 km behind the cold front over the Pacific Ocean. These thunderstorm systems have average cloud top temperatures ranging from -25 to -40°C and average horizontal areas of 8500-40,500 km2 at the -20°C isotherm. They are much smaller than thunderstorm systems over the U.S. high plains in the summertime. The average maximum occurrence rate of sprites is 7.7 per hour in category 1, while the occurrence rates in categories 2-4 are only 2-3 per hour. In each of the four categories of thunderstorm systems, winter sprites in Japan tend to be induced by positive cloud-to-ground lightning discharges occurring in the convective core region during the developing stage where and when convection becomes most active spatially and temporally. Copyright 2005 by the American Geophysical Union.