Inter-Comparison of Development Mechanisms of Explosive Cyclones over the Japan Sea and Kuroshio/Kuroshio Extension

The inter - comparison of development mechanisms of explosive cyclones (ECs) at different stages over the Japan Sea and Kuroshio/Kuroshio Extension was examined by case studies and composite statistical analyses based on the ERA5 data and diagnostic method. The most rapid intensification cases over the Japan Sea and Kuroshio/Kuroshio Extension (referred to as EC1 and EC2, respectively) were selected for the diagnostic analyses using the Zwack-Okossi equation. The results showed that the key factors contributing to the explosive development varied with regions and explosive-developing stages. The main contributor to the initial explosive development was the warm-air advection for EC1 and diabatic heating for EC2. From the initial explosive-developing moment to the maximum-deepening-rate moment, the cyclonic-vorticity advection and diabatic heating for EC1 and the cyclonic-vorticity advection and warm-air advection for EC2 enhanced quickly and contributed to the maximum explosive development. The order of the change for each factor between the two moments in composite statistical analyses (57 ECs over the Japan Sea and 74 ECs over the Kuroshio/Kuroshio Extension) was consistent with the case studies. Moreover, changes of the cyclonic-vorticity advection and diabatic heating for ECs over the Japan Sea and the cyclonic-vorticity advection and warm-air advection for ECs over the Kuroshio/Kuroshio Extension had significant correlation with the change of the deepening rate, supporting the results of case studies.