about 6°F along latitude 20°N, increasing to about l6°F in the Sargasso 

 Sea, about 20*^ in the Gulf Stream, and about 30°F in coastal waters. 

 Surface temperature anomalies cause the actual range for any one year to 

 vary from the mean annual range. The mean annual range of surface temper- 

 ature between 20° and 70°N in the North Atlantic is about h6°F. Annual 

 temperature oscillations and average anomalies occurring at these two 

 latitudes increase the range to about 55°F« 



The annual march of temperature below the thermocline is essentially 

 a trigonometric function of time expressed in a manner similar to eq.uation 

 (l). However, there will be different mean annual temperatures, amplitudes, 

 and lag angles for each depth and location. It is not possible to compute 

 and plot mean monthly temperature charts for subsurface levels as can be 

 done for the surface. Sufficient data for constructing such charts will 

 not be available for some time. Therefore, this study attempts to deter- 

 mine the main characteristics of temperature distribution and to devise 

 a temperature prediction method at a level close to the thermocline but 

 always below it during seasonal stratification and in the mixed layer in 

 winter. 



Existing BT data are satisfactory only for limited areas (near weather 

 stations) to depths of only ^i-OO feet; therefore req.uired conditions for 

 formulation of a prediction method are approached closest at UOO feet but 

 are not optimum. In rather wide zones of tropical convergence the ^lOO-foot 

 level is often in the upper part of the thermocline in winter and in the 

 lower part of the thermocline in summer. At temperate and higher latitudes, 

 the 400-foot level is in the thermocline during the transition period in 

 autumn. Temperature at the Uoo-foot level is always subject to internal 

 wave oscillations. 



The mean annual temperature range at UOO feet in the North Atlantic 

 seldom exceeds U°F at a given location; however, temperature anomalies at 

 400 feet are generally of the same magnitude as surface temperature anoma- 

 lies. Therefore, temperature osci2J.ations at 400 feet may more than double 

 the normal annual range at a given location. 



The mean annual temperature range at i<-00 feet for the area between 

 20° and 70°W is about ko'^ — approximately 10°F smaller than the surface 

 range. This range is considerably augmented by anomalies. 



Temporal anomalies of temperature at 400 feet, although usually 

 related to surface anomalies, often have quite independent characteristics 

 and origins. 



Short-term oscillations caused by internal waves at 400 feet do not 

 occur at the surface. On the other hand, short-term oscillations caused 

 by diurnal heating processes at the surface are imperceptible at 400 feet. 



