Added effective wind forcing to bulk parameterization

[arango]

Added a new C-processing option WIND_MINUS_CURRENT to compute the effective wind forcing by subtracting surface ocean currents to input wind components in bulk_flux.F:

#ifdef WIND_MINUS_CURRENT
!
!  Modify near-surface (2m or 10m) effective winds by subtracting the
!  ocean surface current (J Wilkin). See:
!
!  Bye, J.A.T. and J.-O. Wolff, 1999: Atmosphere-ocean momentum exchange
!     in general circulation models. J. Phys. Oceanogr. 29, 671-691.
!
      DO j=Jstr-1,JendR
        DO i=Istr-1,IendR
          Uwind(i,j)=Uwind(i,j)-                                        &
     &               0.5_r8*(u(i,j,N(ng),nrhs)+u(i+1,j,N(ng),nrhs))
          Vwind(i,j)=Vwind(i,j)-                                        &
     &               0.5_r8*(v(i,j,N(ng),nrhs)+v(i,j+1,N(ng),nrhs))
        END DO
      END DO
#endif

Many thanks to John Wilkin for coding and evaluating this option.

References:

Bye, J.A.T. and J.-O. Wolff, 1999: Atmosphere-ocean momentum exchange in general circulation models, J. Phys. Oceanogr., 29, 671-691.

Sandery, P.A., G.B. Brassington, A. Craig, and T. Pugh, 2010: Impacts of Ocean-Atmosphere Coupling on the Tropical Cyclone Intensity Change and Ocean Prediction in the Australia Region, Mon. Wea. Rev., 138, 2074-2091, doi: 10.1175/2010MWR3101.1