Figure 3 shows a comparison of two expressions of the diurnal varia- 

 tion: The mean range of the ratios, AD, called relative diurnal varia- 

 tion, and xjjnax - xjminj called the absolute diurnal variation, averaged 

 for stations grouped by latitude during the months of June, July, and 

 August. Figure 4 shows the same comparison for stations grouped by geo- 

 graphic region. 



The amount of absolute diurnal variation, xjmax - xjmin) was high in 

 the Pacific Northwest and along the gulf, and appeared to be the highest 

 in the 25 to 35 latitude group. These relations correspond to what is 

 qualitatively known about sea breeze frequency in these areas. 



A study of gage records at Pt. Mugu, California, by Esteva (1972] 

 resulted in the conclusion that daily variations in wave height are at 

 a maximum from April to June. This roughly agrees with Figure 4 which 

 shows that absolute variation for two stations in California is greater 

 in June than in July or August. 



Frequent occurrence of sea breeze has been reported for the gulf coast 

 and the southern Atlantic regions (Hsu, 1970; Yu and Wagner, 1970; 

 McPherson, 1970), and is supported by wind data in the gulf (CERC Littoral 

 Environment Observations (LEO), unpublished; unpublished twice daily wind 

 reports from the Crystal Beach Pier) . 



During May, June, and July 1972, wave observations were made twice 

 daily at Crystal Beach Pier between 0530 and 0830 hours and between 1430 

 and 1630 hours. For 132 observations, the mean breaker height of the 

 morning observations was 2.2 feet and the mean height of the afternoon 

 observations was 2.3 feet. On 39 percent of the days the afternoon 

 height was larger than the morning; on 23 percent of the days the morning 

 height was larger than the afternoon height; on 38 percent of the days 

 the morning and afternoon heights were equal. 



At Grayton Beach State Park, Santa Rosa Beach, Florida, 15 miles east 

 of Crystal Beach Pier, wave observations were made twice daily during May 

 and June 1972. For 90 observations, the morning mean breaker height was 

 1.7 feet, and the afternoon mean was 1.9 feet. The afternoon heights 

 were larger than the morning 47 percent of the days, smaller 24 percent 

 of the days, and equal the remaining 29 percent of the days, which was in 

 fair agreement with the data from Crystal Beach Pier. 



IV. CURVE CLASSIFICATION 



The ratio, Dj (eq. 1), for wave height during June, July, and August 

 was plotted versus time of day for the 17 COSOP stations. The resulting 

 curves, consisting of three lines connecting four points, are characterized 

 by: 



D. = largest value on curve, 

 J max 



10 



