The algebraic signs of index values 

 representing tangential wind components are 

 positive for winds blowing with the corre- 

 sponding ocean currents and negative for 

 opposing winds. Considered in this sense, 

 the annual cycles for the Westerly, Oyashio 

 and Alaska indices are nearly 180° out of 

 phase with those for the Kuroshio, Califor- 

 nia cind Trade indices. Opposing winds 

 (negative index values) occur over the 

 Oyashio and Alaska currents in summer and 

 over the Kuroshio current in winter. 



The year-to-yesir variability for given 

 months, as indicated by the standard devia- 

 tion lines, is generally greater for winter 

 than for summer months. However, for the 

 Kuroshio and Alternate California indices, 

 the variability is quite uniform throughout 

 the year. Moreover, in these two cases the 

 monthly variability is small relative to 

 the seasonal amplitude, in contrast to 

 other regions (Westerly, Trade, Oyashio and 



Alaska) where it is comparable in magnitude 

 or larger than the seasonal ajujlitude. 



The cross-current components, listed 

 in table 4 (page 92), provide a measure of 

 the meridional air flow in the region of 

 the North Pacific Drift. The mean monthly 

 cross-current values are shown graphically 

 for locations 3a-6a in figure 6. North- 

 ward components are plotted as positive 

 values and southward components are nega- 

 tives. Compared to the zonal components, 

 in the Westerlies, the magnitudes of the 

 mean cross-current components are smjill, 

 with pressure differences generally less 

 than three millibaxs. The seasonal pat- 

 terns differ considerably at the different 



< 



s 



I 



UJ 

 o 



a. 



3 



DEC JAN FEB MAR APR MAY JUN JUL AUG SEPT OCT NOV DEC 



DEC JAN FEB MAR APR MAY JUN JUL AUG SEPT Oa NOV DEC 



Figure 5a, b, c, --Grand monthly means of pressure differ- 

 ences for period 1926-57. (a) Kuroshio index, (b) 

 Westerly index; (c) Trade index. The vertical lines 

 drawn through each point extend one standard devia- 

 tion above and below the monthly mean values. 



Figure Sd, e, f. --Grand monthly means of pressure differ- 

 ences for period 1926-57. (d) California index; (e) 

 Alternate California index; (f) Oyashio index. The 

 vertical lines drawn through eacli jx)int extend one 

 Standard deviation above and below the monthly 

 mean values. 



