e above)  size(dt_tr,4) = number of tracer

        Tri_surf -- type(surf_diff_type)
             information needed to pass 
               => surface modules => gcm_vert_diff_up
	       
     output: 
     
        dissipative_heat -- real, dimension(:,:,:)
             shape must conform to that of u, v, t, etc
	     units: deg_K/s 
	     
	     (computed when do_conserve_energy = .true.
	      and added to dt_t before temperature is diffused)

     optional input:

          kbot -- integer,dimension(:,