Analyses and calculation facts of the baroclinic term in synoptic-scale motion over tropics

Analyses are made of all terms in the vorticity equation for the atmosphere at low latitudes by using the scale analysis theory, with the result that for synotic-scale motion the baroclinic term, i. e. the twisting term and the vorticity vertical-transport term, approximates in order to the relative-vorticity advection, divergence andβ term. With intensified atmospheric disturbance ratios of theβ term to others become smaller while the others stay in more or less fixed proportions between them. This statement has been confirmed by the results of 22 typhoons calculated covering a large area in low latitudes. Besides, the baroclinic term for the genesis and development of 6 typhoons over 1979–1980 is calculated and the results obtained show that it has significant effect. Finally, the baroclinicity is shown not to be ignored in dealing with synoptics and dynamics of synoptic-scale systems such as typhoons and easterly waves.