from April to November are relatively low and 

 average 28cal. cmT^day"' and 56 cal. cmT^day"', 

 respectively. From December to March these 

 interyear differences, however, are an order of 

 magnitude larger (table 6). 



Consider next lat. 17° N., long. 152° W. (table 

 B) in the trade wind zone, where the variations 

 of Q(E) are large and where the most pronounced 

 interyear differences occur during January to 

 April (fig. 5). Table 7 lists average values of 

 Q(E) and Q(N) for the 4 months January to April. 



Finally, in the equatorial zone, lat. 2° N., 

 long. 157° W. (table B, fig. 6), interyear dif- 

 ferences are primarily reflected by the net heat 

 exchange across the sea surface. From No- 

 vember 1964 to May 1965, Q(N) was larger than 

 during the same months 1 year earlier. Table 

 8 lists average values of Q(E) and Q(N) for the 

 4 months November to February, the period of 

 largest interyear difference in Q(N). 



The illustrations based on the results of ta- 

 ble B show that interyear differences of Q(E) 

 and Q(N) during the 2-year period under con- 

 sideration were larger than the variations to be 

 expected from the data uncertainties discussed 

 earlier in this paper. Furthermore, the inter- 

 year differences in the northern zone and in the 

 trade wind zone are probably underestimated. 



The interyear differences in the northern 

 zone and in the trade wind zone are also con- 

 sistent with the monthly mean sea-level pres- 



Table 6. --Interyear differences of Q(E) and Q(N), 

 lat. 32° N., long. 167° W. (from table B) 



Table 7. --Interyear differences of Q(E) and Q(N) , 

 lat. 17° N., long. 152° W. (from table B) 



sure distributions (Northern Hemisphere charts 

 of mean sea-level atmospheric pressure. Ex- 

 tended Forecast Division, National Meteoro- 

 logical Center, Environmental Science Ser- 

 vices Administration). During the winter and 

 spring of 1964, the trade winds were well de- 

 veloped and contributed to the large evapora- 

 tion rates in the trade wind zone. During the 

 winter of 1965 the trade winds were weak and 

 the northern zone came under the influence of 

 the Northwest Pacific circulation. In conse- 

 quence evaporation rates were high in the 

 northern zone but low in the trade wind zone. 



Table 8. --Interyear differences of Q(E) and Q(N), 

 lat. 2° N., long. 157° W. (from table B) 



CONCLUSION 



Despite the limitations of the marine surface 

 meteorological data, meaningful measures of 

 the month-to-month and year-to-year changes 

 in the large-scale heat exchange processes have 

 been obtained for a large portion of the North 

 Pacific trade wind region. The results pre- 

 sented in table B, therefore, satisfy the needs 

 of the TWZO investigation. 



Beyond this application, the need for monthly 

 measures of large-scale, sea-air interaction 

 processes in the trade wind zone will continue 

 and increase; the experience gained in the prep- 

 aration of this paper may be of help in future 

 work. Some suggestions to facilitate the calcu- 

 lations and improve the results are therefore 

 made. 



The mechanics of processing large quantities 

 of meteorological and oceanographic observa- 

 tions for the computation of sea-air interaction 

 processes are still in the developmental stages. 

 In the work reported here, quality control pro- 

 cedures involved laborious visual inspection of 

 original data. Obvious errors that were initially 

 overlooked could usually be corrected during 

 the preparation of the smoothed charts. By us- 

 ing the statistics of table A, it is now possible 



17 



