(c) Improved knowledge of wave climate. The effects documented in 

 this paper, including the fact that some of the effects are surprisingly 

 small, add to the store of wave climate information available for coastal 

 engineering design. 



VIII. SUf-MARY 



This study examines the diurnal variation in visually observed breaker 

 height for 17 COSOP stations and two other sites on the coasts of the 

 United States. The results are as follows: 



1. An increase in average height in the afternoon or early evening, 

 the expected result of a sea breeze, occurred at 88 percent of the sta- 

 tions in June, 94 percent in July, and 82 percent in August. 



2. Differences between the largest and smallest mean heights for 

 different hours within the day (average absolute diurnal variation) were 

 0.1 to 0.3 foot. The Pacific Northwest and gulf area had the largest 

 variation, followed by the southern Atlantic and California. 



3. Observations made twice daily at two gulf locations in early 

 summer of 1972 showed that the afternoon height was larger than the 

 morning height 39 and 47 percent of the time, and less than the morning 

 height 23 and 24 percent of the time. At both stations the mean after- 

 noon wave height was slightly higher than the morning mean. 



4. Correlation between absolute diurnal variation and coastal expo- 

 sure indicate that stations with a large sector of exposure have less 

 frequent and smaller afternoon increases in height and period than sta- 

 tions with limited exposure. 



5. Stations with large mean breaker heights also tend to have smaller 

 diurnal variations in wave height. 



6. An approximation for wave height that combines swell and the sea 

 breeze-generated wave and considers the frequency of occurrence of sea 

 breeze, gives a plausible indication of why the mean observed variations 

 due to the sea breeze are small. 



