A Study on Westerly Troughs near Japan (III)

Abstract

This is the final report o n our analysis during winter months. The model of the large-scale atmospheric disturbance which was suggested in former reports is made more complete through wind field analysis. It becomes clear that there is a rather close relation between the trough and the divergence field, and that the middle layer divergence in front of the trough is not only an important factor on the cyclone development, but also acts as frontogenesis resulting in the so-called polar front. The vertical motion caused by divergence field explains the characteristic temperature field accompanied by a trough. This seems also to be applicable to the disturbance of a larger scale, such as revealed by 5-day mean.