ON THE DEVELOPMENT OF BLOCKING RIDGE ACTIVITY OVER THE CENTRAL NORTH PACIFIC.

Abstract

Monthly mean atmospheric data taken over the North Pacific during the period 1950 - 70 are used to investigate blocking ridge activity over the central ocean. The blocking ridge is observed to be a finite-amplitude, quasi-stationary long wave, most often centered over the North Pacific at 170W, superimposed upon the quasi-zonal mid-latitude westerlies. The development and behavior of this ridge are analyzed. The data suggest that this regional blocking activity owes its existence to the marine environment. To test this idea, appeal is made to some theoretical work by G. J. Haltiner. In addition to good scale agreement with observations, Haltiner's theory is able to explain both the seasonal and year-to-year variability in blocking activity in terms of corresponding fluctuations in sensible heat transfer and the strength of the mean westerly winds.