Abstract
In this paper, a diagnostic analysis is made for a kind of explosive cyclone over East Asia and the West Pacific Ocean in cold season, using the level III FGGE dataset. The cyclone started developing at 0000 UTC 30 March, 1979. Q vector analysis shows that ageostrophic wind was obvious in cyclone region. The calculation of different kinds of frontogenetical functions indicates that the development of cyclone was closely related to baroclinicity, especially, at lower levels. Isentropic analysis revealed the three-dimensional structure of cyclone development, that is, ascent of southerly warmer current and descent of northerly colder current existed around the cyclonic center during the developing process of the cyclone and is very favourable to the release of available potential energy and generation of eddy kinetic energy. Not only shear component, but also curvature component of upper level jet contributed to the explosive development of the cyclone. The computation of convergence of moisture flux demonstrated that the moisture probably came from the tropical ocean. The distribution of water vapor supply in this case was very advantageous to the deepening of cyclone, especially, during the well-developing period. Comparison between East Asia-Pacific case and North America-Atlantic case (Ogura and Juang, 1990) has been conducted. The common characteristics were that there existed strong baroclinicity in both cases. However, in the latter case, the latent heat release was of secondary importance and in our case, moisture also played very important role in certain stages of the cyclogenesis, especially, during well-developing stage when it moved over oceanic surface.
Published Version
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