A Study on Westerly Troughs near Japan (III)

Abstract

This is the final report on 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.

On the Vertical Structure of Disturbances in a Baroclinic Atmosnhere

“…On the other hand, judging from the experience stated above, the non-divergent layer in winter may be sought on a somewhat lower level as was inferred by MATSUMOTO, ITOO and ARAKAWA [4].…”

“…In our previous reports (MATSUMOTO, 'Too and ARAKAWA [2], [3], [4]) we analysed the time sections of the atmosphere over Japan during four months in winter, January and February of 1950 and '51. The anomalies from the averages of the months were taken in order to make clearer the feature of the relative situation, and some remarkable structures were commonly found in each of the four months.…”