devap_datmos -- real, dimension(:,:)
             shape must conform to first two dimensions of input fields
             Set = 0.0 if the surface flux is treated explicitly
             If dependence of flux on lowest level of atmosphere is
             treated implicitly, set 

                dtau_du = derivative of surface stress with respect to 
                     zonal wind component in lowest model layer.
                     Units = kg/(m**2 s)

                dtau_dv = derivative of surface stre