The Trade Wind Zone Oceanography Pilot Study 

 Part IX: The Sea-Level Wind Field and Wind Stress Values 



July 1963 to June 1965 



By 



GUNTER R. SECKEL, Oceanographer 



Bureau of Commercial Fisheries Biological Laboratory 

 Honolulu, Hawaii 96812 



ABSTRACT 



Wind observations and derived wind stresses are summarized in 5° square 

 units of the area lat. 0° to 35° N., long. 130° to 170° W., for each month. The re- 

 sults complement time-sequence oceanographic observations of the Trade Wind 

 Zone Oceanography Pilot Study in the area lat. 10° to 26° N., long. 148° to 157° W., 

 February 1964 to June 1965. The sources and processing of wind observations, 

 and the computations to obtain 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 are described. The results are consistent with monthly wind 

 stresses computed from long-term mean winds over the North Pacific. Despite 

 inadequacies in the distribution and quality of data, the wind and wind stress 

 summaries are adequate for interseason and interyear comparisons. 



INTRODUCTION 



This report contains monthly summaries of 

 sea-level wind observations and the derived 

 wind stresses at the sea surface in the area 

 bounded by lat. 0° and 35° N. and long. 130° and 

 170° W., July 1963 to June 1965. The wind data 

 and wind stress values, in addition to other me- 

 teorological properties and heat exchange pro- 

 cesses that were published previously (Seckel, 

 1970), complement the TWZO (Trade Wind 

 Zone Oceanography) Pilot Study oceanographic 

 data (Charnell, Au, and Seckel, 1967a, 1967b, 

 1967c, 1967d, 1967e, 1967f). 



The TWZO Pilot Study was designed to fur- 

 ther an understanding of the mechanisms that 

 change the distribution of sea-water properties 

 and water masses in the North Pacific trade 

 wind zone (Seckel, 1968). The meteorological 

 processes are an essential part of these mecha- 

 nisms; e.g., the heat exchange processes affect 

 the heat budget and the wind stress affects the 

 momentum budget of the ocean. 



The areas of the TWZO oceanographic and 



meteorological observations are outlined in 

 figure 1. The oceanographic field work took 

 place from February 1964 through June 1965 in 

 the area between lat. 10° to 26° N. and long. 148° 

 to 157° W. Oceanographic stations in a fixed 

 grid were occupied at monthly intervals. 



Oceanographic conditions that were observed 

 are intimately related to the behavior of the 

 trade wind system. The area of interest, there- 

 fore, encompasses the region of strongest trade 

 winds, which is located between the North Pa- 

 cific high- and the equatorial low-pressure re- 

 gions. Because the results reported here begin 

 in July 1963, they antecede and cover the oceano- 

 graphic study period. 



The wind data and wind stresses for every 

 month of the 2-year study period are presented 

 in two tables: Table A contains means of the 

 observed and derived values per 5° square, and 

 table B contains interpolated values based on 

 smoothed charts. 



The sources of data, methods of processing 

 and computation, and an evaluation of the re- 

 sults, are presented below. 



