     i.e, longitude index ranges from is to is + size(dt_t,1) -1
                   latitude index ranges from js to js + size(dt_t,2) -1

         delt -- real
           time step , seconds
           if using leapfrog step, set equal to 2*dt = time(i+1) - time(i-1)

         Tri_surf -- type(surf_diff_type)
             information passed from  information 
               surface modules and gcm_vert_diff_down 


         dt_t, dt_q -- real, dimension(:,:,:)

             The tendencies modified by the e