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The extratropical cyclone is one of the important driving forces of the heat and water vapor transportation from the lower latitude to the higher latitude. As it brings large amount of solid precipitation over the area during cold seasons, its activity would affect the growth and decay of the cryosphere. We analyzed explosively developed cyclones over the Northwestern Pacific area during cold seasons between 1994 and 1999 using a global objectively analyzed data set (GANAL) provided by Japan Meteorological Agency (JMA).
Explosive cyclones were classified into three types by the places of birth and maximum deepening positions. They are Okhotsk and Japan Sea type cyclones, Pacific Ocean - Land type cyclones, and Pacific Ocean - Ocean type cyclones. These types of cyclones have characteristics for their seasonal appearance frequencies and maximum deepening rates. By the composite analysis, it was found that these characteristics are reflected by the interior structures of the cyclone. Water vapor acts as a driving force for the development of the cyclone through the latent heat release and the water vapor is carried into the cyclone center at its maximum deepening. The cyclone reaches its center sea level pressure minimum after explosive development and achieves large horizontal vapor transportation. Vertically integrated horizontal vapor flux and cyclone tracks were analyzed by month and the following tendencies were found: water vapor transports into the Arctic circle over the Kamchatka Peninsula during the Okhotsk and Japan Sea type cyclones predominant month; it zonally transports toward the Gulf of Alaska during the Pacific Ocean - Land type cyclones predominant month; and it transports into the Arctic circle through the Bering Strait during the Pacific Ocean - Ocean type cyclones predominant month.
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