          that have been added prior to this call
             output will be the tendency modified by the 
                 effects of diffusion 
             Units are [xi]/s where [xi] = [u], [v] etc

        dt_tr -- real, dimension(:,:,:,:)
             Tracer tendency (see 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 