anchor.diff:      divu%name="divu"
       allocate(divu%f(1:divu%n), stat=ist)
   
  +    !Gradient of divergence
  +    grad_ed_div%n=mesh%ne
  +    grad_ed_div%pos=edpos
  +    allocate(grad_ed_div%f(1:grad_ed_div%n), stat=ist)
  +    grad_ed_div%f = 0._r8
  +
  +    !Gradient of vorticity
  +    grad_ed_vort%n=mesh%ne
  +    grad_ed_vort%pos=edpos
  +    allocate(grad_ed_vort%f(1:grad_ed_vort%n), stat=ist)
  +    grad_ed_vort%f = 0._r8
  +
  +    !Laplacian at edges
       lapu%n=mesh%ne
       lapu%pos=edpos
       lapu%name="lapu"
  
positive.code: 
      !Laplacian
      lapu%f=0._r8
  
      !PV analysis
      q_tr_exact=q_tr
  
negative.code: 
      !Vorticity
      eta%f=0._r8
      zeta%f=0._r8
      eta_ed%f=0._r8
      q_tr%f=0._r8
      q_ed%f=0._r8
  