Figure 23 shows the distribution of three types of points of k (17) 

 for the At interval of 6° to 8° F. The upper points, designated by square 

 symbols, correspond to convergent conditions; central points (circles) are 

 normal values in the wind field with horizontal flow of pure wind current; 

 and the lower group (triangles) correspond to divergence areas. Each group 

 of points follows the same functional pattern and spreads from the central 

 (normal) group increasingly with k and 17 . The same pattern occurs in all 

 At intervals. Largest p values for all 3 groups of points lie in the At 

 interval of 0° to h° F, and smallest p values for all 3 groups lie in the 

 At interval of l6° to 18° F. 



p values computed for convergence and divergence curves by least 



squares for all available At intervals show a certain variation of the 



P P 

 ratios ^"^"and ^^ within each interval. This variation is probably 



conv norm 

 due to sparsity of data. The total range of variation of these ratios in 

 all At intervals is 0.339 to 0.505; overall distribution of values indicate 

 a constancy of ratio from one At interval to another and no apparent dif- 

 ference between convergence and divergence. Therefore, the mean value of 

 all ratios, O.436, was used for computation and plotting of k(^) curves 

 for convergence and divergence. Constancy of ratios from one At interval 

 to another indicates constant decrease of convergent and divergent effects 

 with increasing stability, because the convergence and divergence curves 

 approach the normal curve as the stability index increases. Logical inter- 

 pretation of this constant decrease indicates that stability resists all 

 mixing forces equally. 



Corresponding equations of convergence and divergence curves for a 

 given At are : 



\onv = [o^ (K - k 'conv) 2 Pnor m ] ,/2 =[4.58p norm (k-k' conv )] |/ 2 (n) 

 \ v =[o.436(k-k , dlv )2p norm ] l/2 =[o.873p norm (k-k' dlv )] ,/2 ( 12 ) 



WhSre ''conv = k 'nor m "^ «* *'d,v = ''nor. +0.07 



Mixed-layer thickness is still correlated to wave parameters which 

 must be taken from the wind field producing convergence or divergence at 

 the point under consideration. This wind field usually lies outside the 

 point of observation. Tnis idea is based on the assumption that the area 

 of observation or prediction was initially in the wind field where normal 

 mixing occurred. Because of propagation of the wind field, the area later 

 became a convergent or divergent zone, and the mixed-layer thickness was 

 altered accordingly. 



The upper and lower solid curves in Figures 15 through 22 for con- 

 vergent and divergent conditions of pure wind current were computed by 

 Equations (11 ) and (12). Only k and 77 values showing no intermixing of 

 normal and convergent or divergent points (transition zones) were used 



51 



