anchor.diff:  
   subroutine evaluate_dvdt(dvdt, h, u, v, b, zeta, wind_y, fv, &
       au, ar, slip, dx, dy, hfacW, hfacE, nx, ny, layers, rho0, &
  -    spongeTimeScale, spongeV, RedGrav, botDrag)
  +    RelativeWind, Cd, spongeTimeScale, spongeV, RedGrav, botDrag)
     implicit none
   
     ! dvdt(i, j) is evaluated at the centre of the bottom edge of the
  
positive.code:         dx, dy, wetmask, hfacW, hfacE, hfacN, hfacS, fu, fv, &
          au, ar, botDrag, ah, slip, &
          RedGrav, g_vec, rho0, wind_x, wind_y, &
          spongeHTimeScale, spongeH, &
          spongeUTimeScale, spongeU, &
          spongeVTimeScale, spongeV, &
  
negative.code:         dx, dy, wetmask, hfacW, hfacE, hfacN, hfacS, fu, fv, &
          au, ar, botDrag, ah, slip, &
          RedGrav, g_vec, rho0, wind_x, wind_y, &
          RelativeWind, Cd, &
          spongeHTimeScale, spongeH, &
          spongeUTimeScale, spongeU, &
          spongeVTimeScale, spongeV, &
  