A Comparison of Momentum Fluxes Determined from Time and Space Structure Functions.
TEXAS A AND M UNIV COLLEGE STATION DEPT OF OCEANOGRAPHY AND METEOROLOGY
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Estimates were made of the rate of turbulent energy dissipation and of the shearing stress at a height of 10 m in the marine atmosphere from measurements taken aboard R.P.Flip during BOMEX, 17-28 May 1969. Two types of structure functions were used in determining energy dissipation rate and shearing stress the mean square of the difference in wind speed between two points aligned normal to the mean wind, D3, and the mean square of the difference observed between two times at a fixed point in space, D2. Comparisons were made between the two methods to improve knowledge of the relationships uniting them. Results indicated a relationship of the form D2 gamma D3 where gamma approx. 0.8 under existing conditions. Further investigation of this relationship is needed in order to interpret properly results obtained from the space-based structure function, which is less affected by platform motion at sea than is the time-based structure function. Related drag coefficients revealed, somewhat unexpectedly, a Neumann-type decrease with mean wind speed over a range of 5-11 msec. Diurnal variations in resulting values of wind stress were also examined and, based on a very limited sample, a semidiurnal variation was indicated. This variation showed an apparent correlation with observed diurnal variations in other meteorological parameters. In addition, computations were made of the universal constant in Kilmogorovs third similarity hypothesis and values obtained were found to agree qualitatively with results of earlier investigators. Author
- Physical and Dynamic Oceanography