Transient Kinetic Energy at 200MB and the Development of Synoptic Disturbances over South America during the Southern Winter

摘要

The calculation of transient perturbation kinetic energy (TPKE) over South American and Australian sectors showed that it is high in the upper troposphere. A preliminary analysis suggested that these two regions are favorable for internal baroclinic instability. In an attempt to identify synoptic disturbances whose development might be linked to baroclinic instability, a case study of a winter disturbance over South America was undertaken. This showed the intensification of a cyclonic disturbance over the continent. The intensification occurred first in the upper troposphere. The disturbance showed several characteristics of baroclinic disturbances such as the eastward propagation, intensification with westward vertical tilt and barotropic decay. However, the vertical tilt was confined to upper levels only. This suggested that the mechanism of development might be somewhat different compared to the usual baroclinic instability associated with low level vertical inclination. Internal baroclinic instability is a plausible mechanism of development.