than is presented here, also contains in chrono- 

 logical order by day and by 1° square the wind 

 speed and direction, the zonal and meridional 

 components of the wind velocity, the square of 

 the wind speed, and the zonal and meridional 

 components of the wind stress. 



I originally planned to summarize the mete- 

 orological data for periods of, possibly, 5 days 

 and then, by summation, obtain values for the 

 monthly sea-air interaction processes. The 

 spatial and temporal distribution of marine ob- 

 servations proved inadequate to permit this 

 procedure, however, so the traditional climatic 

 approach had to be used. 



The wind properties on the data tape were, 

 therefore, summarized by 5° squares and by 

 months and are presented in table A. The sum- 

 maries for each property contain the mean 

 value, the highest and lowest values observed, 

 and the standard deviation if there were more 

 than four observations. The number of obser- 

 vations and the mean location of observations 

 are also given. 



Smoothed charts of the zonal and meridional 

 components of the wind velocity, the square of 

 of the wind speed, and the zonal and meridional 

 components of the wind stress were obtained by 

 hand-contouring the summarized data plotted at 

 the mean location of the observations. In turn, 

 the smoothed charts were used to obtain inter- 

 polated values at the center of each 5° square 

 that are presented in table B. In this table the 

 properties are listed in geographic format to 

 facilitate contouring. 



When table B is used in combination with 

 table A, it is possible to judge the reliability of 

 the results in any area and month covered by 

 this report. 



COMPUTATIONS 



The wind stress is the only derived property 

 listed in tables A and B whose calculation needs 

 discussion. All other properties listed are 

 simply mean values of vector components from 

 which the resultant winds and wind stresses can 

 readily be obtained. The monthly values of the 

 square of the wind speed are based on the 

 squared value of each wind speed observation. 



Malkus (1962), in an excellent summary of 

 the significance of wind and wind stress in 

 large-scale, sea-air interactions, reviewed the 

 method of computation of the wind stress and 

 the limitations of the stress estimates so ob- 

 tained. The formula for the magnitude of the 



wind stress at the sea surface. 

 T = pCDW^ 



is particularly applicable when surface-ship 

 wind measurements are used. In the formula, p 

 is the density of the air, W the wind speed, and 

 C r-, the nondimensional drag coefficient. 



The drag coefficient is the uncertain term in 

 the formula. First, Cj-, varies widely depending 

 on the stability of the air (Malkus, 1962; also 

 see a theoretical analysis of the air-sea ex- 

 change coefficients as a function of stability by 

 Deardorff, 1968). Secondly, the dependence of 

 Crj on the wind speed has not been resolved. For 

 example, Wu (1969) suggested a coefficient that 

 varies with wind speed, but Ruggles (1969) pro- 

 posed a constant for winds from 2 to 10 m. 

 sec."' , Cp = 1.6 X 10"\ 



Computation of large-scale, sea-air interac- 

 tion processes by different workers reflect 

 these uncertainties. In calculation of evapora- 

 tion rates a constant drag coefficient has gen- 

 erally been used (Malkus, 1962). In the compu- 

 tation of the wind stress, different values of the 

 drag coefficient have been used for low (<6.7 m. 

 sec."') and high (>6.7 m. sec."') wind speeds 

 (Malkus, 1962; Reid. 1948). 



In this paper the choice of the drag coefficient 

 for the calculation of the wind stress was based 

 on three considerations: (1) In the study region 

 neutral stability at the height of marine weather 

 measurements can be assumed; (2) relative 

 changes in the wind stress from month to month 

 and season to season, rather than absolute mag- 

 nitudes of wind stress, were the main interest 

 of the TWZO Pilot Study; and (3) because the 

 wind stresses computed at the Scripps Institu- 

 tion of Oceanography (1948) and by Hidaka 

 (1958), based on a drag coefficient with differ- 

 ent values for low and high wind speeds, have 

 been widely applied, the use of drag coefficients 

 giving comparable results is valuable. 



The drag coefficient for neutral stability, 

 which varies with wind speed given by Malkiis 

 (1962: fig. 6, p. 110), satisfies the considera- 

 tions above and has been used to calculate the 

 wind stresses in this paper. The equation 



_ . arctan (W-8 ) , -3 



Cd - [ Y796 + 1-6 J 10 , 



with the wind speed in meters per second, ap- 

 proximates the values given by Malkus and fa- 

 cilitates computation. 



The computer program to calculate the zonal 

 and meridional components of the wind stress 



