Vertical motion diagnostics related to Q-vectors,and the reorganisation of a cold frontal system

Summary Estimates of vertical motion obtained by explicit solution of the quasi-geostrophic omega equation expressed in terms of Q-vectors (Hoskins et al., 1978) were compared with qualitative estimates based on the divergence of Q-vectors. The horizontal distributions of each were broadly similar, but differed in their detail. At any level, the relative magnitudes of centres of vertical motion varied between the parameters. The precise locations of the main centres also differed. Greater differences existed in the vertical distributions of the parameters. The divergence ofQ andF _Q of Hoskins et al. (1978) both reached maximum values in upper levels, whereas peak values of occurred in middle levels. A vertical distribution similar to was achieved ifF _Q was divided by a stability parameter. The diagnosed vertical velocities appeared consistent with the restructuring of a summertime cold front as it crossed waters south of Australia.With 6 Figures