GO-novf

Code to generate localized ME s-coordinates (Bruciaferri et al. 2024) in the Greenland-Scotland ridge region of GOSI configurations to better represent the Nordic overflows.

Quick-start

1. Clone the repository

git clone https://github.com/JMMP-Group/GO-novf.git
cd GO-novf

2. Create and activate conda environment

conda env create -f pyogcm.yml
conda activate pyogcm

3. Create the localisation area

cd src/loc_area/
python generate_loc_msk.py loc_area_novf_gosi10_025.inp 

As we can see from the loc_area_novf_gosi10_025.inp input file, in GOSI10 we use a wider localisation area than in Bruciaferri et al. 2024 - here we target the 2930m isobath instead of the 2800m one.

The output of this step is a file including the bathymetry and the localisaztion masks that will be used to define the localised multi-envelope terrain-following vertical levels in the proximity of the Greenland-Scotland ridge region - the file for GOSI10@1/4 can be found at ADD ZENODO ARCHIVE!!!

4. Create the envelopes

cd ../envelopes/
python generate_envelopes.py ${input_file}

where inp_file=MEs_novf_gosi10_025_4env_2930_r12_r16-r075-r040-r035_it2-r030.inp is the file used to create the defintive version of the envelopes that are used in GOSI10.

In order to reduce horizontal pressure gradient errors, envelopes are smoothed using the iterative preocedure detailed in Appendix C of Bruciaferri et al. 2024, which uses the Martinho and Batteen (2006) smoothing algorithm to reduce the local slope parameter $r$ below multiple user defined $r_{max}$ values, effectively allowing one to apply distinct level of smoothing in different areas of the model domain. In the case of GOSI10, increasingly more severe $r_{max}$ values were applied only in those grid points where spurious currents were $\geq 0.025$ $m s^{-1}$.

The three months long tests to assess the horizontal pressure gradient (HPG) errors were conducted with the u-di990@301896 suite. Since the u-di990 suite was based on GOSIp1, it didn't include the key_qco which is part of GOSI10p2. Therefore, given the importance of the key_qco, I reconducted the final HPG test with the u-dk586@302161 suite (which is based on GOSI10p2). The suite u-dk586@302161 can replicate the results of u-di990@301896.

All the input files needed to generate and optimise the envelopes can be found here: ADD ZENODO ARCHIVE!!!

The output of this step is a file including the bathymetry, the localisaztion masks and the envelope surfaces that will be used to define the localised multi-envelope terrain-following vertical levels in the proximity of the Greenland-Scotland ridge region - the file for GOSI10@1/4 can be found at ADD ZENODO ARCHIVE!!!

5. Generate the vertical grid

The vertical grid of GOSI10 with local ME s-levels in the Nordic overflows area is generated using the 423-adding-more-flexibility-to-me-gvcs@17eae5a7 development branch of the DOMAINcfg tool.

The namelist_ref and namelist_cfg used to configure the vertical grid of GOSI10 can be found in namelists.

The output of this step is a domain_cfg.nc file - the file for GOSI10@1/4 can be found at ADD ZENODO ARCHIVE!!!

6. Horizontal pressure gradient error

7. Comparison with GOSI9

GOSI9 --------------------------

GOSI10 --------------------------

The strange canyon that can be seen in the first sections of GOSI9 are due to the fact that in the case of GOSI9 the bathymetry has been modified by hand as shown in the following map:

8. INITIAL CONDITION FOR GOSI WITH LOCALALISED ME s-coordinates

Because of the way NEMO interpolates the T&S fields passed in input when initialising from rest (ln_tsd_init=.true.), the following two important point MUST be considered when initilising a model with localised ME levels (ln_sco=.true. and ln_loczgr=.true.):

1. Since the land-sea mask will be different in the localisation area, The T&S used to initialise the model should be flooded, i.e., continents should be filled with value from the ocean to avoid issue when interpolating in the vertical.

2. When using local GVC s-coord, the last level must be a copy of previous level:

ori_S=woa13v2.omip-clim.abs_sal_gosi10p1-025_flooded.nc
new_S=woa13v2.omip-clim.abs_sal_gosi10p1-025_flooded.MEs.nc
ori_T=woa13v2.omip-clim.con_tem_gosi10p1-025_flooded.nc
new_T=woa13v2.omip-clim.con_tem_gosi10p1-025_flooded.MEs.nc

ncap2 -O -s 'so_abs(:,74,:,:)=so_abs(:,73,:,:)' ${ori_S} ${new_S}
ncap2 -O -s 'thetao_con(:,74,:,:)=thetao_con(:,73,:,:)' ${ori_T} ${new_T}