The Northern Monthly

Geostrophic wind components computed from monthly mean atmospheric sea level pressure charts are employed as indices of wind intensity over the principal current systems in the North Pacific Ocean. Pressure differences across pairs of points at 36 locations and deviations from long-term monthly means are tabulated for a 33-year period, 1926-58. The data for certain locations were combined to form regional indices representing wind components tangential to the major North Pacific Ocean currents. The mean seasonal cycles of these indices show marked differences in phase and amplitude for the various regions. Monthly anomalies are found to have generally larger magnitudes in winter months than in other seasons. Some evidence of long-term trends is indicated by graphical representation of time series and decade means. In particular, weak wind components occurred over the Oyashio and Alaska currents during the winter months of the period 1946-55, while over the California current the wind components were stronger, than during the previous decade.