differences than the significance limits determined by eq.uation (13) • 

 The significance limits may be high, because they are based on the en- 

 tire range of variation. However, it shovild be remembered that sharp 

 peaks in the ratio distribution have been eliminated by smoothing. A 

 ■wide margin of safety is desirable; therefore, significance limits de- 

 termined by equation (13) are more realistic by being large. 



In summary, correlated pairs of surface and ij-OO-foot anomalies are 

 defined as those which have the same sign and do not differ in magnitude 

 by more than k2 percent of the larger value of a pair plus O.5 F. All 

 other pairs are considered uncorrelated. 



The third set of correlation coefficients in table 5 were computed 

 according to this definition with elimination of only part of the un- 

 correlated anomalies. If uncorrelated pairs determined by equation (13) 

 had also been excluded, the correlation coefficients would be consider- 

 ably larger. About 70 percent of anomalies at both levels in the Worth 

 Atlantic are correlated; the remainder are uncorrelated. 



VII. PREDICTIOIJ TECHNIQUE 



A. Mean Temperatuje at 400 Feet 



Mean temperature at 400 feet can be computed by use of equations 

 (9) J (10), (11), or (12)^ depending on the area under study. In order 

 to apply the equations, 9^ q, the mean annual surface temperature, and 

 A, the annual amplitude of mean monthly surface temperature at the given 

 point, must be known. 



Mean annual surface temperatures, computed with more than 100 

 years of data, are plotted in figure 2 at intervals of 1*^ except for 

 the Gulf Stream where 2°F intervals were used to prevent crowding. The 

 annual amplitude of mean monthly surface temperature (half annual range) 

 is plotted in figure 11 at 0.5°F intervals. 



Computations of mean temperatures are rather time consuming; 

 therefore, graphic representations of the equations are given in figures 

 A-1 through A-4 (appendix A). These nomograms contain four parts for 

 each equation. In the first part, the harmonics are computed with the 

 amplitude, A, factored out. For example, the graph in the upper left 

 of figure A-1 represents: 



The nomograms are used as follows: 



A straightedge place horizontally from a point representing a 

 given latitude and time in the upper left of each nomogram intersects the 

 annual amplitude in the upper right of the nomograms (Ko = K-,A). A 

 straightedge placed vertically from this point intersects the given 

 latitude in the lower right (K, = K2 - 7.^^ cos 4> )• Horizontally from 



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