Boundary layer mixing

The parameterization of boundary layer mixing coefficients follows the local vertical diffusion scheme of Holtslag and Boville (1993). In KMCM, a slight modification has been introduced to the Richardson criteria in order to ensure that their derivatives are continuous. For l=1,…,lev-1, the diffusion coefficient is defined on half model layers as

The diffusion tendencies are defined in section 4.1, and ka 0.4 is the van Kàrman constant. The surface coefficient yields