GO-iniTS

Code to generate T & S fields compliant with OMIP protocol to initialise GOSI configurations.

According to OMIP-1 (Griffies et al. 2016) and OMIP-2 (Tsujino et al. 2020) protocols, OMIP simulations are initialised with temperature and salinity taken from WOA13.v2:

Potential temperature and practical salinity are initialized in the upper 1500 m using January observational-based climatology from version 2 of Locarnini et al. (2013) for temperature and Zweng et al. (2013) for salinity. We refer to these data as WOA13v2. The January fields from WOA13v2 stop at 1500 m. We filled deeper depths with the mean from January/February/March (winter in the north and summer in the south). Initial conditions are provided at the OMIP website, with both 1 ◦ and 1/4 ◦ versions. Interpolation should be made to the respective model grid. Conversion to Conservative Temperature and Absolute Salinity should be made for models based on IOC et al. (2010).

The initial temperature and salinity fields are therefore each a composit of two different variants:

1. upper 1500m: January mean (averaged decades between 1955-2012)
2. below 1500m: seasonal mean (Jan-Feb-Mar; all decades)

The Geomar CMIP6-OMIP/OMIP-input repository provides an example of the workflow and the code to generate an initial ocean state in agreement with OMIP protocol.

The documentation for WOA13.v2 dataset can be found here. WOA13v2 datset includes in-situ temperature and practical salinity. Therefore, in order to use this data to initialise our TEOS10 based configurations they need to be converted in Conservative Temperature and Absolute Salinity first.

Quick-start

1. Clone the repository

git clone [email protected]:JMMP-Group/GO-iniTS.git
cd GO-iniTS

2. Create and activate conda environment

conda env create -f pyogcm.yml
conda activate pyogcm

Generating WOA13v2-based initial condition following OMIP protocol

Before running the code, make sure to adapt the Input parameters section of each script to your needs.

1. Download WAO13v2 data

cd src
./download_woa13v2_data.sh

2. Generate T/S initial condition

python  generate_iniTS.py

N.B: on Met Office machines, this script is run using SLURM with the submit_generate_iniTS.batch script file.

3. Generate a mesh_mask.nc file for WOA13v2 data

python create_woa_mesh_mask.py

N.B: on Met Office machines, this script is run using SLURM with the submit_create_woa_mesh_mask.batch script file.

Remap WOA13v2-OMIP fields onto eORCA-025 grid with $z$-coordinates

We use the suite u-cx924@289674 (accessible by anyone able to access Monsoon) to remap WOA13v2-OMIP Conservative Temperature and Absolute Salinity fields onto eORCA-025 grid. The suite carries out the following tasks:

1. Uses the the SCRIP (available also ESMF) package to compute the interpolation weights to remap from WOA13v2 regular lat-lon horizontal grid onto the orthogonal curvilinear eORCA-025 horizontal grid with bi-linear interpolation.
2. Computes the interpolation weigths to remap from WOA13v2 $z$-levels onto eORCA-025 $z$-levels with partial steps using linear interpolation (in-house code).
3. In the case of the WOA13v2-OMIP datset, extrapolates T and S values from coastal wet cells onto land cells using a python version of the seaoverland NEMO module.
4. Applies the previously computed horizontal and vertical remapping weights to remap the "filled-flooded" WOA13v2-OMIP fields onto the eORCA025 mesh.

The following rose-suite.conf@289674 file is used in case of GOSI10-025 (30 iterations of seaoverland are used).

How to use the WOA13v2-OMIP_eORCA-025 T/S fields to initialise GOSI10p1.2

While testing the new initial condition with GOSI10p1.2, I found that we first need to conduct a 10 days long run with Smagorinsky viscosity to ensure that the run is stable and after using the restart from this simulation to initialise the lopng simulation with the standard viscosity. The same procedure was needed also with GOSI9-12 but not with GOSI9-025.

The suite u-dg800@289603 was used to run the 10 days long simulation and create the restart for the longer GOSI10p1.2 simulation. The suite u-dg878@289746 was used to run the 33 years long GOSI10p1.2.

For clarity: GOSI10p1.2 is the release of GOSI10 with new bathymetry, JRAA-55do forcing and WOA13v2-OMIP initial state.