116 



Water 



those of surface currents (which average 

 about 10 cm/ sec), with the greatest differ- 

 ence present when the winds followed and 

 added to the surface currents and the two 

 currents were separated by a thermocline. 



An effect of currents near shore commonly 

 encountered by swimmers is the presence of 

 warm spots. These may be as much as 3°C 

 warmer than the surrounding water, and 

 commonly they are conical to lens-shaped, 

 as though in response to their relatively low 

 density. Diameters range up to 16 meters 

 and depths are rarely as much as 4 meters 

 (Smitter, 1955). They originate from several 

 kinds of traps in which water is held until it 

 becomes abnormally warmed by insulation 

 before it escapes to the sea. Among the 

 traps are kelp barriers, tide pools, small bays 

 or estuaries, points projecting into longshore 

 current, oil slicks, and perhaps pinched-off 

 slicks. 



Waves 



Wind Waves and Swell 



Near Point Arguello wind stream lines 

 show a flow of air from the northwest, but 

 south of that point the stream lines fan out 

 into the broad embayment off southern Cali- 

 fornia. This pattern results in an area of 

 high wind velocity in the northwestern cor- 

 ner of Chart I bordered by concentric zones 

 of progressively lower wind velocity to the 

 east and southeast (Anonymous, 1956^). 

 Although daily winds may depart from the 

 annual average, the pattern is fairly constant 

 (Fig. 102). During the night and early morn- 

 ing a land breeze occasionally reaches as far 

 as 10 miles out to sea, but during the late 

 morning and afternoon the westerly pattern 

 of stronger winds becomes re-established. 

 On a smaller scale land breezes occur on 

 each of the islands. During all seasons, but 

 chiefly in summer, there may be superim- 

 posed on the general pattern a counterclock- 

 wise eddy centering north of Santa Catalina 

 Island and named the CataUna Eddy (Gra- 

 ham, 1950). A smaller one farther northwest 

 is known as the Point Arguello Eddy. The 

 general pattern is also sometimes interrupted 



Figure 102. Prevailing winds. Average annual stream 

 lines and wind velocities (meters/sec) and those for a 

 typical day having well-developed examples of the Cata- 

 lina Eddy and the smaller Point Arguello Eddy. Adapted 

 from Graham (1950). 



for periods of several days in all seasons ex- 

 cept summer by strong dry winds named 

 Santa Anas which blow seaward down slopes 

 and valleys from the desert area (Bailey, 

 1954). Once in a while the region is also 

 reached by largely spent hurricanes from off 

 Mexico; the latest such storm occurred in 

 September, 1939. Most storms, however, are 

 part of winter systems which move into the 

 region from the northwest, west, or south- 

 west (Todd and Wiegel, 1952). Except dur- 

 ing these storms, the winds in the offshore 

 area south of Point Arguello are of low 

 velocity during the winter, giving rise to 

 lower average wind velocities in winter than 

 in summer. 



