depth, assuming that temporal variability of the exponent -would be accounted 

 for by the cosine terms in the equation. In that case, exponent, phase 

 angle variation, and reduction of mean annual temperature at a given level 

 with respect to the surface must be determined individually by empirical 

 means. 



These parameters can be determined by Fourier expansion of the long- 

 term mean temperature distribution at the surface and at UOO feet in the 

 same location. Variability of parameters with latitude can be determined 

 by conveniently combining two or more locations. This course is followed 

 below . 



B. Areas of Data 



Derivation of practical eq.uations for temperatiire distribution at 

 400 feet requires adequate simxiLtaneous data at the surface and 400 feet. 

 Obviously, only BT data are available for this purpose, and only BT traces 

 reaching 400 feet can be applied. This requirement eliminates more than 

 half of extant BT observations. 



Data collected for the ocean weather stations are as follows: 



Location Period Number of observations 



BRAVO (56°30'N, 51°W) 

 CHARLIE (52°U8'N,35°30'W) 

 DELTA (i^4°N, 4l°W) 

 ECHO (35°N, 480W) 

 HOTEL (36°n, 10^) 



In addition to data from the ocean weather stations, data were 

 obtained from the National Oceanographic Data Center for the following 

 areas delineated in figiure 1. 



Area Number of observations 



F 290 



G hk2 



H subarea Hi jk 



H2 2l]-9 



H3 62k 



\ 322 



The data collected in areas F, G, and H were assiimed to be valid 

 for the mean latitude (^) of each area. The number of useful observations 

 was considerably larger than given above; however, some large groups of 

 data covered restricted areas in relatively short periods of time, in 

 which case, only one or a few of the observations were used for computing 

 the long-term mean. 



1955-1960 



3,563 



19i^5-1958 



3,598 



19l|Jj._1958 



2,251 



1944-1958 



7,669 



1944-19 5^^ 



2,710 



