Figure 2. — Comparison of total heat transfer values (cal/cm^/day) 

 taken from Seckel (horizontal axis) and this report (vertical axis). 

 Each of the 24 monthly values for the period July 1963 to June 1965 

 was averaged over the region lat. 20 to 35'N and long. 130° to 170°W. 



for which the comparison was made, wind speeds 

 were less than 7 m/sec in about two-thirds of the cases 

 for June through September and greater than 7 m/sec 

 in about two-thirds of the cases for November through 

 February. These factors combine to make Sectcel's 

 computed values of heat loss by evaporation lower 

 than ours in the warming season and greater in the 

 cooling season, which is reflected by his higher max- 

 imum and lower minimum values of net heat flux 

 shown in Figure 2. 



Computations of heat exchange at the sea surface 

 have also been carried out by Wyrtki ( 1966) who pre- 

 pared charts of heat loss by evaporation and of total 

 heat exchange for the Pacific Ocean north of lat. 20°S. 

 Wyrtki's charts are based on marine synoptic weather 

 observations taken during the period 1947-60. The 

 equations used for computation of the various compo- 

 nents are equivalent to those described in this report, 

 except for differences in certain empirical constants 

 which give Wyrtki larger values of heat loss by evap- 

 oration and conduction under otherwise similar condi- 

 tions. Wyrtki's method of data processing also differed 

 from that of Johnson et al. (1965). Considering all cir- 

 cumstances, however, results obtained with the equa- 

 tions and procedures of Johnson et al. (1965) for a 

 given set of data would probably agree as well or bet- 

 ter with corresponding results from Wyrtki's method 

 than with Seckel's. 



Since Wyrtki's charts represent a time period an- 

 tecedent to the 1 1 yr covered by our charts, they af- 

 ford an opportunity to verify climatological patterns of 

 net heat flux and, with caution, to infer changes in 

 such patterns. We will make no attempt at interpretive 

 comparison in this respect, other than to point out a 

 few of the main characteristics in the mean cycle of 

 heat exchange. 



The beginning of the cooling season is first evident 



in September in the northernmost part of the Gulf of 



Alaska and in an area west of long. 155°W between lat. 

 35° and 45°N . However, large positive heat flux values 

 still occur at this time of year along the North Ameri- 

 can coast south of lat. 45°N. By October, the mean net 

 flux is generally negative north of lat. 25°N, except in 

 coastal areas out to about long. 125°W. From October 

 through January, negative heat flux is most intense in 

 the Gulf of Alaska and west of long. 150°W, between 

 lat. 25° and 45°N. Heat loss is minimal between lat. 45° 

 and 5()°N west of long. 165"W, and our charts show an 

 area of positive heat flux off southern California and 

 Baja California in every month except December. 

 Wyrtki's charts include all of these features and, in 

 addition, show small areas of positive heat flux even in 

 December. In February, positive values of heat flux 

 appear in coastal areas south of lat. 40°N, out to long. 

 125°W. The largest negative flux of heat at this time 

 occurs south of lat. 30°N, from long. 165° to I7()°W 

 according to Wyrtki's charts and somewhat north and 

 west of that area on our charts. 



March is a transition month with marked intensifica- 

 tion of positive heat flux south of lat. 40°N from the 

 coast out to long. 125°W, while the flux elsewhere is 

 both positive and negative and generally weak. The 

 principal features in the heat exchange pattern which 

 characterize spring and summer are the areas of max- 

 imum positive heat flux along central and northern 

 California and to the west of long. 150°W at lat. 30° to 

 35°N. Wyrtki also found a relative maximum along the 

 southern stretch of Baja California which does not ap- 

 pear on our charts because of the cutoff east of long. 

 115°W. A relative minimum in the pattern occurs in 

 the vicinity of long. 130°W at about lat. 20° to 25°N. 

 Our charts show a negative flux in this area in every 

 month except August and September. Wyrtki found 

 negative values in the same area in every month ex- 

 cept July and September. 



The values of net heat flux computed by Wyrtki 

 differ from those presented in this report by 50 

 cal/cm-/day or more in many areas. Such differences 

 may reflect dissimilarities in data distribution, 

 methods of processing or real climatological trends. 

 The main features in the mean seasonal patterns of net 

 heat exchange depicted by our charts appear, how- 

 ever, to be well substantiated by comparison with 

 those of Wyrtki. 



ACKNOWLEDGMENTS 



The authors express their thanks to Albert J. Good 

 and Dorothy D. Roll for special programming and 

 technical assistance and to Gunter R. Seckel for his 

 thorough review of the original manuscript. 



LITERATURE CITED 



BERLIAND. M. E.. and T. G. BERLIAND. 



1952. Opredelenie effektivnovo izluchenia zemli s uchetom vli- 

 jania oblachnosti (Determination of effective radiation of the 



11 



