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


Here, Zr is the roughness length which has a constant value of 10-3 m in the present model experiments.