34 



Inversions were characteristically present in thermograms 

 from the outfall areas. Evidently the turbulent nature of the 

 boil is the primary cause of these thermal variations „ As the 

 warm effluent leaves the pipe it mixes with bottom water and 

 moves toward the surface as a more or less fractured mass, 

 A bathythermograph lowered into the area of an outfall will 

 thus intercept alternate zones of poorly mixed, unstable water. 

 Typical inversions at the Hyperion outfall were present on 

 July 20, 1956 „ Figure 9 shows the vertical temperature pro- 

 file along a line extending from the boil to a distance of 

 6 miles from shore . Figure 10 is a detailed representation 

 of the area near the boil. The deflection of the 54° to 61°F 

 isotherms reflects the entrapment of cold bottom water by the 

 rising boil and its subsequent rise toward the surface. 



Inversions were encountered frequently in the southern 

 reaches of the bay and in the offshore portions of the north 

 and north-central areas. Here the inversions appeared to be 

 due to a horizontal overlapping of different water types. 

 These warmer bodies of water must have had a sufficiently 

 high salinity to make them stable under such circumstances. 

 In all cases the inversions were of small magnitude and the 

 level at which they occurred was well above the major boundary 

 between the warm surface layer and the colder subsurface water. 



A peculiar inversion was encountered in only two or three 

 instances near the bottom of the central bay shelf. There is 

 no obvious explanation for such a warm layer in that area and 

 at that depth. In any event, it is not of major significance 

 in the thermal structure of the bay. 



