-- real, dimension(:,:,:)
             pressure at full model levels
             size(p_half,3) must = size(t,3)
             units = Pascals

         z_full -- real, dimension(:,:,:)
             height of the levels where t, q, u, v, tr are defined
             shape must conform to that of xi
             units = meters

	 dtau_du, dtau_dv  -- real, dimension(:,:)
	     shape must conform to first two dimensions of input fields
	     Set = 0.0 if the surface flux is treated explicitly. If
	     depende