SWOT Interpolation - time of ocean model output SSH

[oj-tooth]

Name of your institution / research group

Marine Systems Modelling Group, National Oceanography Centre

Information request

Hi, I’m just getting started on preparing our Near-Present Day eORCA025 & eORCA12 daily SSH (2024) outputs for interpolation onto the SWOT grid using the synthocean package and the SWOT dataset made available through the package’s README.md.

Would you be able to clarify how you would like us to choose the time of the model output SSH variable to interpolate onto each SWOT swath grid. Since there is no temporal interpolation performed, do we need to manually select the SSH output file with a timestamp which is closest to each SWOT swath? In which case, the resulting interpolated SSH dataset will be structured the same way as the SWOT grid dataset (many swaths for each cycle). How would this translate to interpolating SSH for a neutral output years if output for 2024 is not be available?

Thanks in advance for your help!

Ollie

[contreras-m]

Thank you for your interest! Here are the answers to your questions:

1. You must manually select the date, taking into account the closest date to the SWOT date.
2. Yes, it will have the same structure as an SWOT L3 expert file.
3. If you do not have the year 2024, you will have to assume that the year you select will have the same cycle as the year 2024.

Let me know if I have not clarified your questions.
However, I must warn you that due to the holiday season, our responses will be slower. But we will be back the week of the 25th.

[abarthele]

Hello,

I was testing out the processing of our model outputs, and I was asking myself the same questions. This issue helps me understand what I should do, but just to be sure... Assuming that I have a file with daily SSH for 2024, I should do:

for each cycle_0??: 
    for each file in the cycle: 
        ./model2SWOT.py (...), using model_timestep_index to select the time frame in my output file (e.g. the day appearing in the SWOT file name)

There are some much-needed clarifications in the README of synthocean:

• [latitude_var_name, longitude_var_name, time_name, time_index are not what the code expects] => not true
• the "path to the directory containing the SWOT data files" cannot be specified, only a specific file
• I suspect it is the same for "the output directory where results will be saved"

Antoine

[haguedjou]

Hello [abarthele]
Before you fill in the variable names latitude_var_name, longitude_var_name, time_name, time_index , you should first specify --model-lat-var , --model-lon-var , --model_timestep_index etc.
The command be like : ./model2SWOT.py -m path_to_your_model_file -k path_to_your_model_mask_file -s path_to_swot_data_file -o path_to_output_file -i interpolator --model-lat-var latitude_var_name --model-lon-var longitude_var_name --model-time-var time_name --model_ssh_var the_model_ssh_variable_name --model_timestep_index time_index
So, terms in bold must be entered first. By this way the code will run

Yes, currently only a specific SWOT file can be specified. This is an important point that we will work on to allow the simultaneous specification of multiple SWOT files.

Same as the output directory, but you can create an output directory where to save your interpolated data files

[abarthele]

@haguedjou My bad indeed, I mixed up the parameter keys and values...