On the Seasonal Variation of Upper Flow Patterns

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Abstract
Over the Far East the jet, as well as the 5-day mean trough, is extremely stationary in position and strength during winter. It is a peculiar feature in this region that two distinct cases of break-down of the steady patterns, showing sudden weakening of the jet, persistent establishment of splitting, sudden dissipation of mean trough, etc., take place at the beginning of April and in the middle of May.An analysis of the 500-mb charts leads us to suggest the existence of a long-period disturbance, prevailing all over the northern hemisphere and consisting of two principal stages which we may call S stage and B stage. So far as the height change patterns of the 500-mb surface between the two stages are concerned, it looks as if they were accompanying a complicated standing wave the loops of which are fixed near the both borders of the continents, and the period of which is about 40 days. It is, here, of interest that the time of each break-down of steady patterns over the Far East closely coincides with the time of appearance of S stage. We have carried out somewhat detailed consideration concerning the linkage between these two phenomena.