High-Freqaency wave Records 



A variable capacitance wave recorder has been developed for 

 measuring very srfiall and high frequency water waves. The instrument is 

 capable of recording elevation of a fraction of a millimeter, and 

 frequencies up to 60 cps. Hoi-ever, it is found that such sensitivity is 

 achieved at the expense of stability, and that is has not been possible 

 to achieve sufficient stability for field work. In addition, the instrument 

 itself produced a disturbance in the water which makes the analysis of 

 records diificialt. For this reason, photographic methods for measuring 

 these tiny ripples are now being investigated, 



Wind-Stress Investigation 



The experimental phase of the program to determine the stress of 

 the wind over water in the nission Bay model yacht pond ;iras concluded 

 in April. The final report on the project is now nearing completion. 

 The results indicate that tangential friction accounts for about two-thirds 

 of the total stress up to ij.0 mph wind speeds and that normal pressures 

 against wavts account for the remainder. There is some indication that 

 heavy rainfall significantly increases the total stress. Slicks produced 

 by adding detergent to the surface produce a change in the Td.nd profile 

 over the water at higher wind speeds. 



There is a critical wind speed for which the stress against the 

 waves first raakes itself felt. For lesser winds waves do not seem to 

 contribute materially to the total stress. Attempts are being made to 

 interpret these results theoretically. It is now felt that there is a close 

 connection between this critical wind speed and the minimum phase velocity 

 of surface waves. 



Sea-S\irface Roughness from Photographs of the Sun's Glitter 



Analysis of photographs of the glitter of the sun on the sea 

 continues. 



The "fir fit order" terms in the slope distribution are now known. 

 To deterraine such secondaiy features as the skewness and peakedness in 

 the frequency distribution, it becomes necessary to make certain second 

 order corrections in the analysis. Since the distribution of slopes of 

 the sea surface has been related to the intensity of reflected sunlight, 

 it is necessary to correct the observations for that part of the observed 

 intensity due to light from other sources than the sunj i.e., the reflected 

 skylight c.nd light back-scattered from the body of the sea. 



From photographs tal<en on very calm days, when the glitter of the 

 sun is confined to a small area, we have derived a semi-empirical relation 

 betv;een the unwanted intensity on the one hand, and the brightness of the 

 sun together with the estimated sea-slope distribution on the other. 



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