ABSTRACT
Bjerknes’ first works related to undulations in the atmospheric fronts from the Atlantic associated with low pressure during his stay in Bergen. These observations led him to investigate cyclones and the prediction of stormy weather periods. He introduced the notions ‘atmospheric front’ and ‘cold front’ referring thereby to advancing cold air mass. He noted a similarity with hydraulic jumps in open channel flow. The mechanism of cyclone development was inserted in weather cards allowing for a better weather forecast. The scientific contribution of Bjerknes was the concept of the non-diverging level in meteorology. This level is approximately located at an elevation above the ground where the air pressure is half of the ground pressure. This concept allowed Carl-Gustaf Rossby (1858-1957) to develop later the scheme for the daily weather forecast. Bjerknes’ 1957 monograph gives a summary of his developments in meteorology.
