Calculation of sea surface height according to change of reference pressure

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1

Dear all,

I am currently conducting research on predicting storm surge with NEMO-surge. A sensitivity test was conducted by changing the reference pressure in the NAMELIST, but there was no change in the sea surface height (SSH). It was confirmed that the model calculated the equivalent inverse barometer sea surface height(ssh_ib), but there was no change in the final SSH result. I cannot find the part where the reference pressure directly affects the sea surface height (not ocean momentum equation) in the source codes except sbcssm.F90. Is there any other process for calculating SSH?

Thanks in advance,
Soyeon

2

Hi,

Further precisions are needed:

  • I guess you have in your namelist :
    ln_apr_dyn = .true. ! Patm gradient added in ocean & ice Eqs., right ?

  • Is your model global (or do you have open boundaries making use of the Flather scheme) ?

  • When you say “no change in the final SSH result”, are you referring to the total SSH (hence including pressure effects if any) or corrected by the inverse barometer estimate ?

3

Hi,

  • In my namelist :
    ln_apr_dyn = .true. ! Patm gradient added in ocean & ice Eqs. ,
    ln_ref_apr = .false. ! ref.pressure: global mean Patm (T) or a constant (F). ,
    ln_apr_obc = .false. ! inverse barometer added to OBC ssh data

  • The model is regional and has open boundaries(making use of Flather scheme).
    In the current namelist,
    !-------------------------------------------------------
    &nambdy ! unstructured open boundaries
    !-------------------------------------------------------
    cn_dyn_2d = 'flather' ! boundary conditions for barotropic fields ,

  • I mean the total SSH, not equivalent inverse barometer sea surface height.

Thanks for your help.

4

You should use ln_apr_obc=.true. in order to add the inverse barometer component to your elevation data used by the Flather scheme.
Hence, It’s normal that you don’t see anything by changing the reference pressure with ln_apr_obc=.false.. (since this is the gradient of the inverse barometer that is actually used in momentum equations).

5

I got it. I will check this part.

Thanks for your help.