Long-term changes in characteristics of bomb-cyclones around Japan in winter

Abstract

Long-term changes in characteristics of bomb-cyclones around Japan from the former years (1979-1992) to the latter years (1993-2007) were investigated in winter (November – February), using analysis data of Japanese 25-year Reanalysis / JMA Climate Data Assimilation System (JRA/JCDAS). It was found that the frequency of the “bomb”, in which the deepening rate of central sea level pressure was the maximum in the lifetime of each cyclone and the deepening rate was over a criterion, was increased to the east of Japan in the northwestern Pacific and decreased over the north Pacific. Similar changes were identified in the frequency of heavy precipitation. Moreover, energy budget analyses were conducted for two composited anomaly fields constructed for bomb-cyclones in the former years and the latter years. The comparison between them indicated that the change in the development rate of bomb-cyclones was attributed to the change in the energy supply from the condensational heating.