Eq.uatxons (9) throvigh (12) apply to certain water masses. Along 

 boundaries "between the masses, interpolation would probably give the 

 best results. If mean temperatures at 400 feet were computed for the 

 entire North Atlantic, computations in the boundary areas could overlap. 

 Inconsistencies could then be smoothed out. 



B. Determination of the Anomaly at ^00 Feet 



Mean monthly surface temperature charts are presented in 

 appendix B. These charts are based on long-term data, with numerous 

 obsearvations taken by 1-degree squares. Observations in the Labrador 

 Sea, around Greenland, and northeast of Iceland are very limited. 

 Consequently, the isotherms in these areas are not too reliable. The 

 mean monthly temperature for any given time and location can be inter- 

 polated from two charts. The surface temperature anomaly can be computed 

 from observed surface temperature values and appropriate mean monthly 

 temperature charts. The anomalj'- at 400 feet, determined from the svirface 

 anomaly and by use of figure 8, is added algebraically to the mean 

 temperature computed with the appropriate equation. The result is the 

 predicted temperature at 400 feet. 



The exact reliability of anomaly ratios in figiire 8 is unknown. 

 However, the mean error of prediction in 53 tests (735 individual 

 predictions) in the eastern and northern part of the North Atlantic was 

 1.06°F by use of figure 8 and 1.17°F without use of figure 8. The ratio 

 seems to reduce prediction error. The reduction is not apparent from 

 one or two predictions, because the prediction error is sometimes in- 

 creased through application of the ratio correction. However, the 

 statistical evidence given above supports use of the ratio. 



Use of the corrected surface anomaly to predict temperature at 400 

 feet is successful about 70 percent of the time (when anomalies are 

 correlated). A successfiil prediction is one in which the prediction 

 error of temperatiire at ^l-OQ feet is small or moderate. 



Large errors occur when anomalies at the surface and 400 feet are 

 uncorrelated. There is no way of knowing when anomalies are uncorrelated 

 if only stxrface temperatures are available. If mean monthly temperature 

 charts for 400 feet were computed by equations (9) through (12), the areas 

 of uncorrelated anomalies could be detected from daily BT observations 

 taken by various ships in the charted area. The charts would serve as 

 bases for computation and interpretation of anomalies at 400 feet in the 

 same manner that mean monthly surface temperature charts are used for 

 computing surface anomalies. 



BT observations would pinpoint daily locations of uncorrelated 

 anomalies. Superposition of observations from several days or weeks would 

 outline areas of uncorrelated anomalies. Further superposition should re- 

 veal more definite areas of uncorrelated anomalies and the nature of their 



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