undisturbed sea level (or above the highest wave crests). 



Most of the observations seem to indicate that with an adia- 

 batic lapse rate in the lower layers above the sea surface the 

 observed wind profile can be approximated fairly well by a loga- 

 rithmic law within a certain height interval. However, in the lowest 

 layers, some 50 or 100 cm above the crests of the sea surface rough- 

 ness elements (waves), the logarithmic curve gradually steepens 

 more and more when approaching the "sea surface". This feature is 

 characteristic for the observed wind profiles over the rough sea 

 surface, and a careful analysis of the observations shows that the 

 logarithmic law for the wind profile just above the waves is a 

 rather questionable approximation. 



The value and accuracy of wind profile measurements with cup 

 anemometers for evaluating the wind stress at the sea surface have 

 been discussed in some detail by the author (1949, 195D. There 

 are mainly two facts which make this method unfit for stress com- 

 putations: 



First of all, the questions remains open as to what level has 

 to be chosen as the "height of the sea surface", or, in other words, 

 what is the "sea surface" in the case of an air-sea interface with 

 traveling waves? Any attempt to derive a vertical wind profile 

 from observed wind speeds at fixed heights above the crests, re- 

 quires a clarification of this question. 



Secondly, wind measurements with cup anemometers at fixed 

 heights above the wave crests are unfit to derive true average wind 

 speeds over the rough sea surface. The wind at a fixed height over 

 the trough of a "wave" may have only 40^ - $0% or less of its speed 

 over the crest. With steep waves, even a "lee-eddy" may develop 



37 



