As long as measurements of the instantaneous wind field over the ocean 

 waves are not available, the average vertical wind profile should at least 

 furoish us some useful information which can be interpreted in the light 

 of the turbulence theory developed and checked by means of measurements in 

 laboratories or over land. Now a real trouble begins! I would not like to 

 si)end much time describing the observational problems , but let me only 

 mention this: There are two possibilities of fixing the height of a certain 

 mean wind speed: 



(1) One can take the average distance from the wavy sea surface. 

 This can be done by placing the anemometer on a fixed construction or on a 

 floating base that does not pariiicipate substantially in the wave motion. 

 No measurements in the wave troughs are taJcen in this case . 



(2) The measurements are made at a point that has the same distance 

 from the wave sea surface at any instant, i.e. the anemometer oscillates 

 with the sea surface. This can be realized by using a float or a buoy as 

 carrier of the instrument. In this case, measurements may include the 

 trough region. 



Up to now, it is not clear which procedure gives the better estimate of the 

 mean wind profile . Naturally, the influences coming from the fixing of the 

 zero level will only be significant in the immediate vicinity of the waves. 

 Unfortunately, this is the very height range where the vertical wind profile 

 is of particular interest and importance. 



Apart from such observational difficulties, there are the problems of 

 interpretation of the results . During the last years we were very happy 

 that the majority of the vertical wind profiles measured showed a log- 

 distribution which can be easily interpreted in terms of the turbulent 

 boundary layer theory. Out of 26 studies I reviewed, ik reported a log- 

 profile, 3 could explain their deviations from the log- profile by the 

 influence of thermal stratification, 3 did not say anything about it, 

 because the wind speed was only measured at 2 levels (which certainly is 

 the easiest way) and only 6 papers, mostly published before 1950, reported 

 a pronounced deviation from the log- profile in the lowest levels (below 

 2 m) . The occurrence of such a "kink" in the wind profile could, however, 

 be explained by observational errors (determination of heights) or by dis- 

 turbances originating from the carrier of the instruments, e.g. from the 

 ship, float, etc. Thus, the validity of the log-profile appeared to be 

 well established also for the marine boundary layer under adiabatic con- 

 ditions, and many conclusions about the aerodynamic roughness and the 

 friction coefficient of the sea surface as well as the wind stress at the 

 sea surface were based on this fact. 



Quite recently, however, some doubt has been shed on the validity of 

 the log-profile for representing the mean vertical wind distribution over 

 the sea. For instance, Takeda (1963) and others found a kink in the 

 lower part of every log-profile they measured over the sea and, after having 



