East Asia and Western Pacific METEOROLOGY AND CLIMATE

Study on the Frontal Cyclone System in Southern China and the Vicinity
of Taiwan Area during Late - Winter and Early-Spring
Huo-Ming Jiang
Institute of Atmospheric Physics
National Central University
Chung-Li, Taiwan 32054
ABSTRACT
The structure of the upper level and stationary surface
frontal zones associated with a cyclone developing over southern
China on 3-5 February 1979, is examined and discussed. The
dynamics of the transverse circulation which plays important
role in the frontogenesis process is also discussed .
From the cross-section analysis of the potential vorticity
structure, it was shown that the upper sub-tropical front was
caused by the tropopause folding of high potential voricity
stratosphere into the troposphere, but the stationary surface
frontogenesis was caused by the sub-geostrophic flow whicg was
induced by the Tibetan Plateau.
1. INTRODUCTION
According to the three-cell meridional circulation model
(Palmen,1951), the hemispheric airis divided into three principal air
masses : tropical air mass, mid-latitude air mass and polar air mass. The
polar fronts are considered as the boundary between polar and mid-latitude
air masses. The contrast between these two air masses on the poleward edge
of the Ferrel cell is relatively distinct in the low and middle troposphere
and less distinct higher up. Owing to the low-level divergence in the
boundary region between the Hadley and Ferrel cells, there is no marked
air-mass boundary in the lower troposphere. A contrast between tropical
and mid-latitude air is found in the upper troposphere where there is
meridional convergence between these circulation cells.
Fig.l (after Palmen and Newton, 1969) shows the typical structure of
the northern hemisphere. The scheme is most applicable to the atmospheric
structure during the cold season when all features are more pronounced
than during the warm season. The subtropical front is indicated as a
sloping upper-tropospheric layer between the tropical and the mid-latitude
air masses.
Cyclogenesis frequently happened in the East China Sea during latewinter
and early-spring (Fig.2). According to the results of Hanson and
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