Intraseasonal oscillation enhancing C5 typhoon occurrence over the tropical western North Pacific

Abstract

Abstract This study reveals that the atmosphere‐ocean coupled intraseasonal oscillation (ISO) enhances the occurrence frequency of Category 5 (C5) typhoons in the western North Pacific (WNP). Climatologically, the major region of C5 typhoon occurrence in the WNP is collocated with the intraseasonal variance of outgoing longwave radiation and tropical cyclone heat potential. The active convection and large ocean heat content associated with ISO create an environment conducive to the occurrence of C5 typhoons. Between 1980 and 2009, approximately 82% of C5 typhoons occurred when one or both of the two conditions were fulfilled. Our results suggest that compared with the thermodynamic factor of ocean heat content, dynamic factors (i.e., convection and near‐surface moisture convergence) within the favorable intraseasonal background state likely play a more influential role in inducing C5 typhoons.