### Dynamic boundary conditions

At the bottom boundaries, no-slip conditions are prescribed for the horizontal velocity components:

 (8)

With (7), also holds at the bottom. It should be noted already here, that the bottom boundary condition (8) is generally not directly used in numerical ocean models, since the near-bottom values of the horizontal velocity components are not located at the bed, but half a grid box above it. Instead, a logarithmic velocity profile is assumed in the bottom layer, leading to a quadratic friction law, see section 8.13.9.

At the surface, the dynamic boundary conditions read:

 (9)

The surface stresses (normalised by the reference density) and are calculated as functions of wind speed, wind direction, surface roughness etc. Also here, the drying parameter is included in order to provide an easy handling of drying and flooding.

kklingbe 2017-10-02