SEAWAY 



19 



Table 5 Wave Data Obtained in Sun-Glitter Observations of Cox and Munk (1954) 



" Wind was measured at the lieights of !1 and 41 ft. The mean value, corrps|)oiiding ajiproximatelj' to the often-used "anemometer 

 height" of 24 ft is listed here. 



' The wave periods and heights were recorded. The listed values of wave length X and celerity c are obtained from Table 3 of Ap- 

 pendix A for the corresponding periods. 



c/V added. The a- are .shown plotted against wind 

 speed in Fig. 14 and the probability distribution of ir- 

 is shown in Fig. 15. This latter will be discussed later in 

 connection with the statistics of the irregular sea. 



The major conclusions can be given by a partial Cjuota- 

 tion from the summary of Cox and Miuik (1954): 



a) As a first approximation the slope distribution is 

 ff)und to be Gaussian; this can be accounted for by an 

 arljitrarily wide continuous spectrum of ocean waves, 

 but not by a spectriun consisting of a few discrete fre- 

 quencies. 



b) The ratio of the up/down wind to crosswind com- 

 ponents in the mean square slope is less than two; this 

 indicates the directional "l)eam width" in excess of 130 

 deg for the relatively shcjrt waves that constitute the 

 slope spectrum. 



c) The mean square slope, regardless of direction, in- 

 creases linearly with wind speed and reaches a value of 

 (tan 16°)^ for a wind speed of 14 mps (about 45 fps or 27 

 knots) ; this empirical relation follows in form and to an 

 order of magnitude from a spectrum proposed by Neu- 

 mann on the basis of wave-amplitude observations. A 



spectrum proposed by Darloyshire cannot he reconciled 

 with our observations. 



d) Oil slicks laid by the vessel over an area of V4 sq 

 mile reduce the mean square slope by a factor of 2 or 3. 



Sc\'eral conclusions of les.ser importance for the present 

 monograph pertain to statistical properties of records 

 and are omitted in the foregoing quotations. The dis- 

 cussion of statistics and spectra will be deferred until 

 later chapters on irregular seas, and only the featiu'es 

 bearing on the next section, on jMunk (1955), will be dis- 

 cussed here. 



This work is extremely valuable in introducing an in- 

 genious technique based on statistics, in providing very 

 valuable data on the sea surface, and in discu.ssing statis- 

 tical relationships for the sea surface. The conclusions 

 appear, h<jwever, to be too broadly stated in some re- 

 spects, without regard to the limitations of the relatively 

 small scope of observations. An examination of the 

 wave data in Table 5, particularly of the columns of 

 \/H and c/V shows that the obser\'ed significant waves 

 are mostly either too small or too large in relation to the 

 observed wind. The former case indicates that either 



