Meaning of variables in ''gridded_posterior.nc" and "inversion_result.nc" datasets.

[elenagjyli]

Name: Elena Gjyli
Institution: University of Aarhus
Hi everyone :),
After running the inversion with IMI version 2.0, I get these files: ''gridded_posterior.nc and "inversion_result.nc".
When opening them with xarray in Python I can see that those datasets contain the next variables:
'ScaleFactor','S_post' and 'A' in the first nc file and 'KTinvSoK','KTinvSoyKxA','ratio','xhat','S_post' and 'A' in the second nc file.
Is there any documentation of what those variables represent?
We need to know what exactly those variables mean so we can be able to create the right graphs.
Thank you!

[msulprizio]

The output file gridded_posterior.nc contains the following variables projected onto the 2D inversion grid:

• ScaleFactor: posterior emission scale factors
• S_post: diagonal elements of the posterior error covariance matrix
• A: diagonal elements of the averaging kernel matrix

The output file gridded_posterior.nc contains the following variables projected onto the 2D inversion grid:

• xhat: Posterior scaling factors
• KTinvSoK : K^T*inv(S_o)*K (part of inversion equation, see code snippet below)
• KTinvSoyKxA: K^Tinv(S_o)(y-K*xA) (part of inversion equation, see code snippet below)
• ratio: Change from prior (aka delta_optimized where xhat = 1 + delta_optimized])
• S_post: Posterior error covariance matrix
• A: Averaging kernel matrix

integrated_methane_inversion/src/inversion_scripts/invert.py

Lines 86 to 88 in 0dc30a6

	# = xA + inv(gamma * K^T*inv(S_o)*K + inv(S_a)) * gamma * K^T*inv(S_o) * (y-K*xA)
	# (--------------) (-----------------------)
	# Expression 1 Expression 2

These variables are documented in the code but I will work on adding some text to our documentation and possibly to the netCDF files for clarity.

[msulprizio]

See also the visualizatrion_notebook.ipyb (also included in the inversion output directory) for sample python code for plotting those output and the existing documentation at https://imi.readthedocs.io/en/latest/other/listing-directory-contents.html.