[MITgcm-support] How to include tides by the atmospheric pressure like the tidal forcing in LLC4320

[Dimitris Menemenlis]

Hi Chengyan,

If you want to recreate atmospheric forcing for LLC4320, the atmospheric pressure plus tidal forcing is available here:
https://ecco.jpl.nasa.gov/drive/files/ECCO2/atmos/ECMWF_operational

However, since the LLC4320  simulation was carried out, better ways to include tides in MITgcm have been implemented:

1. Jean-Michel Campin added the capability to prescribe tidal forcing separately from atmospheric pressure forcing.  Search for “tidePot” in https://github.com/MITgcm/MITgcm/tree/master/pkg/exf

2. Oliver Jahn integrated the JPL SPICE library in MITgcm, see: http://mailman.mitgcm.org/pipermail/mitgcm-support/2023-May/013438.html

If you carry out a regional simulation in. A large domain, you will need to apply both tidal currents at the lateral boundary conditions as well as tidal potential using one of the two methods above.

Dimitris


> On Nov 28, 2024, at 7:08 PM, whale <250107302 at qq.com> wrote:
> 
> Dear MITgcm users
> 
> I am trying to configure a regional model with tides included. The usual way is to prescribe the barotropic tidal forcing at the open boundaries of a regional model, and I can do it with this method in my regional model.
> 
> However, if the model domain is relatively larger, it would be better to prescribe the tidal potential at each bin than the tidal forcing on open boundaries. It seems that the well-known LLC4320 experiment successfully added tides by using tidal potential at every grid.
> 
> The tidal forcing of LLC4320 is documented by Rocha et al. (2016) as follows:
> 
> 'The model also includes tidal forcing for the 16 most significant components that are applied as additional atmospheric pressure forcing (A. Chaudhuri 2014, personal communication).'
> 
> Rocha, C. B., Chereskin, T. K., Gille, S. T., & Menemenlis, D. (2016). Mesoscale to Submesoscale Wavenumber Spectra in Drake Passage. Journal of Physical Oceanography. 46(2), 601-620. https://doi.org/https://doi.org/10.1175/JPO-D-15-0087.1
> 
> Then, I read the 'data.exf' of LLC4320 at http://mitgcm.org/viewvc/MITgcm/MITgcm_contrib/llc_hires.
> 
> The 'data.exf' of LLC4320 shows some information as follows:
> 
> ‘apressurefile     = 'EOG_pres_tide',’
> 
> It looks like the tides are prescribed by the atmospheric pressure forcing files of 'EOG_pres_tide'.
> 
> I have not found more documentation of the tidal forcing descriptions of LLC4320 from http://mitgcm.org/viewvc/MITgcm/MITgcm_contrib/llc_hires
> 
> So, I have the following question.
> 
> 1) Where can I get the tidal forcing data like‘EOG_pres_tide’used in LLC4320?
> 
> 2) If I have the atmospheric pressure forcing fields with tidal forcing, can the tidal forcing be included by directly applying the atmospheric pressure forcing to the model with the 'data.exf'?
> 
> 3) Is there anything else I should care about when I use the atmospheric pressure forcing to included tides?
> 
> Any comments or suggestions are warmly appreciated.
> 
> Cheers
> 
> Chengyan
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