33.2.4.2 Vertical mixing coefficients

After computing the Richardson number, both vertical mixing coefficients are computed at the bases of their respective cells for rows 2 through jmw-1 in the memory window

$$diff\_cbt_{i,k,j} \frac{fricmax}{(1 + 5\cdot rit_{i,k,j})^3} + diff\_cbt\_back$$ = (33.10)

$$visc\_cbt_{i,k,j} \frac{fricmax}{(1 + 5\cdot riu_{i,k,j})^2} + visc\_cbu\_back$$ = (33.11)

In regions of vertical instability, the mixing coefficients are set to their limiting values.

$$visc\_cbt_{i,k,j} visc\_cbu\_limit \;\;(for \;\; rit_{i,k,j} < 0)$$ = (33.12)

$$diff\_cbt_{i,k,j} diff\_cbt\_limit \;\;(for \;\; riu_{i,k,j} < 0)$$ = (33.13)

Typically, $diff\_cbt\_limit$ is set to 10⁶ cm²/sec when option implicitvmix is enabled. Otherwise it is set to fricmax. The value of $visc\_cbu\_limit$ is set to fricmax regardless of whether option implicitvmix is enabled or not.

To account for the effect of high frequency wind mixing near the surface (which is absent in climatological monthly mean wind stress), the mixing coefficients at the base of level one are taken as the maximum of the predicted mixing coefficients and parameter windmix.

$$diff\_cbt_{i,k=1,j} max(windmix, diff\_cbt_{i,k=1,j})$$ = (33.14)

$$visc\_cbu_{i,k=1,j} max(windmix, visc\_cbu_{i,k=1,j})$$ = (33.15)