TM No, 377 



For all geophysical fluid motions are, after all, irrotational to varying 

 degrees. The quasi-oscillatory nature of some modes of motion shmil ii not 

 alter the fact that they have strong stochastic (random) attributes. Setting aside 

 all preconceptions of what types of motions are turbulent and what are not, 

 one should ask simply? what are the statistics and the defined turbulent 

 characteristics of a given set of motions represented by a series of care- 

 fully taken velocity data? The following is a brief resume of early and 

 recent experiments in which attempts were made to record turbulent or 

 oscillatory fluctuations, both in the ocean environment and in the laboratory. 



In Situ Measurements - Thorade (1934 ) made measurements of velocity fluc- 

 tuations in the Kattegat using the Rauschelback current meter (Von Arx, 1962), 

 He derived records of speed and direction every 10 seconds and found fluctua- 

 tions having periods of several minutes, 



Mossby (1947;, 1949, and 1951) used arrays of revolving cups at various 

 heights above the bottom in the Alvoestrommen near Bergen, and in the open 

 ocean (at a depth of 100 meters) near the Viking bank about 100 km from the 

 coast, 



Doodson (1940), who is widely known for his valuable contributions to 

 the measurement and analysis of tides s designed a current meter that re- 

 sponded to oscillations up to 1 cps. This meter was used by Bowden and 

 Proudman (1949) for near-bottcm measurements in the river Mersey near Liver- 

 pool, The variances of the horizontal velocity along with the mean current 

 and the auto-covariance functions were determined for various depths, 



Bowden and Fairbairn (1952) used a pair of Doodson meters mounted at 

 various vertical separations on a rigid staff to obtain the spatial vari- 

 ability (and j, hence, the instantaneous shear flow) as a function of depth. 



Probably the first attempt to measure simultaneously the horizontal and 

 vertical velocity components at a point in the water column was reported by 

 Francis g Stommel, Farmer, and Parson (1953), This work is of interest here 

 because it represents a direct, if not a daring, effort to measure turbulent 

 quantities in the ocean and to make some quantitative analysis regrading 

 these heretofore little known and little understood phenomena. Estimates 

 were made of turbulent fluctuations of momentum, heat, and salinity in the 

 vertical, while occupying anchor stations in the Kennebec Estuary, Maine, 

 It is worthwhile to describe these experiments in some detail. 



A somewhat crude but novel type of instrumentation was developed to de- 

 tect both the horizontal and vertical velocity components simultaneously, 

 A propeller meter (Von Arx, 1950), which served to detect horizontal flow, 

 was used in conjunction with a pivoting vane device, which oscillated in the 

 vertical about a horizontal rod on its leading edge. The vane rod was coupled 

 to the shaft of a watertight potentiometer, which was wired in series to a 

 fixed voltage source aboard ship. The outputs of both systems were recorded 

 aboard ship on a strip chart recorder. 



