dU 

 V dz ' """"^^ " n 



-1 



with a step length of I — '^ where T = — is the vertical time scale 



The jump rate for conditions described in the previous paragraph, „008 sec 

 then requires that a velocity gradient of 4 sec be present to obtain 

 diffusion coefficients of 10 gm cm sec . Such a gradient obviously 

 cannot be present, and so diffusion probably takes place as a result of 

 existing horizontal eddies having a large scale. 



Some idea of the characteristics of the horizontal eddies can be 

 obtained from the horizontal diffusion coefficient, Aj, , and from the 

 maximum rate of energy dissipation, 2x10 ergs gm sec « Thus, 



A„ (4r)^ = Aj^ (^)^ < 2x10"^ 



H dx .. .„ 

 n 



lead to 



u„ < 2 cm sec 



l„ > 5x10 cm 



and a time scale of the order of several dayso The value of these results 

 should be tempered by noting that 1) the expression for the energy dissi- 

 pation applies to shear flows and may be appreciably in error when applied 

 to the ocean, 2) the resulting length scale may be too large to have a 

 meaningful random walk approximation, and 3) the horizontal diffusion 

 coefficient used is based on experiments which were probably obtained over 

 a smaller geographical area than required to obtain good statistical data 

 for the large eddies expected. 



-17- 



