















io* 5 ""- 



9 T 



















6* 





135 130 125 



Figure 11. — Relative frequency surfaces and frequency histograms for July. Data are shown for the 1-degree squares labelled 6 through 10 in the 

 upper left inset. Contours of relative frequency are drawn at intervals of 2.5%. Mean vector wind stress is indicated by an arrow. 



Seasonal Cycle at the Coast 



Time series of the surface wind stress within the 1- 

 degree square areas immediately adjacent to the coast 

 are displayed in Figure 13 as the alongshore component, 

 and in Figure 14 as the onshore component. For these dis- 

 plays, the vector means have been resolved into com- 

 ponents parallel and perpendicular to the coast. The 

 coastline angles were determined by visually fitting a 

 line to the dominant trend of the coast within each 1- 

 degree square. The months are indicated along the tops 

 of the figures. The latitudes of the 1-degree squares are 



indicated on the right and left sides of the figures. Nega- 

 tive values are shaded and indicate equatorward along- 

 shore stress in Figure 13 and offshore stress in Figure 14. 



Several characteristic features are apparent in these 

 figures. South of lat. 40°N there is an equatorward com- 

 ponent throughout the year, implying conditions 

 favorable for coastal upwelling in all months. Off the 

 coasts of Oregon and Washington, the data suggest that 

 upwelling occurs seasonally between the months of April 

 and September. 



Three relative maxima occur in the time/space do- 

 main. Off the coast of Baja California, maximum values 



17 



