150 and 230 feet. The mean thermocline depth is quite constant during 

 individual years. Dispersion over the range "between 80 and 150 feet is 

 attributed to variability of convergence from year to year. Thermocline 

 depths exceeding 150 feet are probably caused by very strong convergence 

 produced by hurricanes passing between OWS ECHO and the east coast of the 

 United States. 



Figure 9 shows the frequency distribution of wind force at OWS ECHO 

 for September for the same 6 years. Wind force was Beaufort 3 or less 

 58 percent of the time. Under existing stability conditions the corre- 

 sponding thermocline depth should be no more than 10 feet. Wind force 

 was Beaufort h and 5> 3^- percent of the time, corresponding to a thermo- 

 cline depth of about 70 feet. The wind was strong enough to cause thermo- 

 cline depths between 70 and 110 feet only 8 percent of the time . 



100 



90 



O 80 



< 



>70 

 u 



60 



50 



2 40 



30 



20 - 



10 



mi 



1 2345678 



WIND FORCE (BEAUFORT) 



FIGURE 9 FREQUENCY DISTRIBUTION OF WIND 

 FORCE AT OCEAN WEATHER STATION 

 ECHO 135° N, 48° W) IN SEPTEMBER 

 (6 YEARS' DATA, 403 OBS) 



There appears to be no semipermanent convergence in the area in spring 

 and early summer, at which time the correlation between mechanical mixing 

 and thermocline depth is approximately the same as at the other Atlantic 

 weather stations. 



15 



