5:15 PM - 6:30 PM
[AAS02-P09] The statistical analysis of the explosively developing extratropical cyclone in northern Japan and Atmospheric blocking
Keywords:explosively developing extratropical cyclone, atmospheric blocking, disaster protection
We used the 40-yr ECMWF Re-Analysis (ERA-40; Uppala et al. 2005), with the full horizontal resolution of 1.125°, available every 6 hours for the period 1960-1999. The subject region in this study extends over the northwestern Pacific region from 20° to 65°N and from 100°E to 180°. Definition of explosively developing extratropical cyclone follows the tracking algorithm proposed by Yoshida and Asuma (2003). Here, merger is defined as the situation in which more than two cyclone trajectories overlap each other. Blocking is diagnosed by a two-dimensional (2D) blocking index derived from daily 500-hPa geopotential gradient according the method of Masato et al. (2012, 2013).
The results show that 1775 explosive cyclones were detected. After the merger, deepening rate becomes the maximum and it is 5.37 [hPa / 6 hour] statistically. The higher latitude explosive cyclones merge in, the higher the deepening rate is. The results indicate that merger often occurs over the Sea of Japan and off the Pacific coast of Kanto region. Furthermore, about 40 % of explosive cyclones are located on southern part of blocking when the velocity of explosive cyclone becomes slowest.