Hs, k, kx, and ky are the significant wave height, wave
number, wave number in x direction, wave number in y
direction, respectively.
The original surface and the bottom stresses are computed
by the drag equation (proportional to quadratic velocity)
but in the coupled model they are related to wave
and sediment and more detail will be presented in Section
total water depth; θ the potential temperature; s the salinity;
ρ the density; patm the air pressure; f the Coriolis parameter;
H.