nce of flux on lowest level of atmosphere is
	     treated implicitly, set = derivatives of surface stress
	     with respect to wind components in lowest model layer.  
             Units = kg/(m**2 s)

        dt_t, dt_q -- real, dimension(:,:,:)
             Tendency of t, q  up to this point
             (The final value of dt_t and dt_q are output by 
              gcm_vert_diff_up)
             Units are [xi]/s where [xi] = [T], [q]


    input/output:

         tau_u, tau_v -- real, dimension(:,:)
  