Seasonal persistence and recurrence of European blocking during 1958–1960

Blocking activity was especially frequent and persistent over Northern Europe during all seasons from late 1958 through 1959 and 1960. Some effects of the blocking on seasonal precipitation are discussed. The initiation and persistent recurrence of the blocking is studied with the help of various mean seasonal charts, particularly those for mid-tropospheric levels.

It is suggested that the physical causes of the blocks lie in complex feed-back phenomena between the atmosphere, the North Atlantic sea surface and the Scandinavian Peninsula (particularly its lack of cold-season snow). The latter two factors appear to serve as conservative links in a feed-back chain, thus providing restorative forcing elements on the general circulation over the area.

Some precursory signs of such long period blocking are suggested by an analysis of the wintertime meridional flow prevailing between southern Greenland and southern Scandinavia.