Blocking action in the northern hemisphere: A Climatological study

Using criteria developed from scientific studies, the blocking situations observed in the Northern Hemisphere during the period 1945–1977 are subjectively assessed and statistically analysed. Earlier findings are largely confirmed while new results are presented on seasonal and secular blocking trends, and the probability of multiple blocking. A catalogue of'664 blocking cases was prepared but is not included here because of its size; however, copies of the catalogue may be obtained from the authors.