A certain initial' stability exists with a given At in the absence of 

 a mixed layer. If the mean stability index remains constant, stability 

 increases from the initial value with increasing mixed-layer thickness. 

 Increase of stability is slow when the mixed layer begins to form and 

 gradually becomes greater as the mixed- layer thickness and At increase. 

 Table 2 lists mixing parameters (k) for various stability indexes before 

 mixing begins. These values apply during initial formation of the mixed 

 layer near the surface. 'In Figures 15 through 22 these k values are at 

 the point where k(*7) = and h(k) = 0. 



TABLE 2 



k VALUES AT INITIAL STABILITY 



Stability index At (°F) 



k 



Stability index At (°F) 



k 



2° (0°-k°) 

 5° (k°-6°) 

 7° (6°-8°) 

 9° (8°-10 6 ) 



0.10 



0.13 

 0.16 

 0.19 



11° (10°-12°) 

 13° (12°-1^°) 

 15° (14°-16°) 

 17° (16°-18°) 



0.21 

 0.24 

 0.27 

 0.30 



7) Curves 



To connect mixing parameter values with stability and wave parameters, 

 another parameter t/ = HT was introduced. EWj is significant wave height, 

 and T max is the period of maximum energy of the spectrum. 77 is used as a 

 measure of sea state for wind waves, k values determined in Equation (6) 

 with known wave parameters and mean mixed-layer thickness (h) values were 

 plotted against rj values computed with corresponding wave parameters for 

 eight groups of At. The resulting distribution of points suggests a para- 

 bolic law. Curves computed for each At group with the equation 



*? -2p(k-k') 



(8) 



readily fit the distribution of points, k in (8) is the value of the 

 mixing parameter at initial stability with the given At, and 



St? 2 (K-k') 

 P ~2 2 (k-k')Z 



determined by the least square method. 



p values for stability index intervals from 0° to 18° F are shown in 

 Table 3« 



29 



