breeze, the sea breeze is apparently stronger at stations with poor 

 exposure than at stations with more open exposure. 



Mean absolute diurnal variation for three breaker height groupings 

 are presented in Table 3. Stations with larger annual means tend to 

 have less diurnal variation. 



Table 5. Absolute diurnal variation for breaker height groupings. 

 Annual mean Number of Mean absolute diurnal variation 

 height group curves July June/July/August 



(ft) (ft) (ft) 



<1.4 



1.4 to 2.0 



>2.0 



2 



10 



5 



0.160 

 0.148 

 0.118 



0.130 

 0.143 

 0.139 



VI. 



ESTD4ATED BREAKER HEIGHTS 



For a windspeed of 10 knots blowing over a 10-mile fetch (a typical 

 sea breeze), a 1. 25-foot-high wave having a period of 2.4 seconds might 

 be expected (U.S. Army, Corps of Engineers, Coastal Engineering Research 

 Center, 1975) . An approximation of height, considering the frequency of 

 occurrence of the sea breeze, would be 



f Ai 2" 

 ^SB "SB 



"s^ 



(1 - fsB) H 



C4) 



where, 



H = approximated height, 



f = frequency of occurrences of the sea breeze, 



H = height of sea breeze-generated wave, 



OD 



H = height of swell. 



Equation (4) with fsg = 0.40, was used to estimate the effect of sea 

 breeze on the mean observed height for selected stations in July (Table 4). 

 The equation provides a plausible explanation of the small diurnal varia- 

 tion found in the monthly averages. Because the sea breeze does not occur 

 every day, and because its effects are masked by superposition on the 

 swell, the examples contained in Table 4 show that the effect of sea breeze 

 on average conditions is small. 



As shown in Table 4, the absolute variation increases with decreasing 

 mean height of the waves (compare observed daily mean with approximated 

 height in Table 4). If average wave conditions are low, the effect of the 



17 



