This is a great project idea and I am extremely interested in joining this project. In particular, I am curious about the representation of the Equatorial Current system and the Equatorial Undercurrent between the different models, something I have looked at recently for several CMIP5 models. @yassir.eddebbar summarized the variables needed for that nicely. Are full oxygen budgets available for any of the models?
From a technical standpoint I agree with @matt-long:
We will rely on packages like xgcm, esmlab, etc. to enable concise expressions for operations like integrals, etc. It is possible shortcomings in these packages will need to be addressed to enable writing elegant, performant, exemplary notebooks.
One of the major challenges of a project like CMIP6 is that the various models provided have different grid architectures, both in the horizontal and vertical. In order to analyze the output between different models we require tools that can calculate properties on the native grid of the model and avoid interpolation and associated errors. The syntax of these tools should be as „agnostic“ as possible so that common operations like a gradient or divergence operator can be applied with a simple syntax akin to an analytical equation. The proposed tools would detect if e.g. the velocities are located on a B or C-grid and then execute the numerical calculations as close to the internal model code as possible.
I would propose the implementation of common vector calculus operators like grad, div, curl into the xgcm module. Recent addition of automatic grid metric handling builds the foundation for these operators and this workshop presents a fantastic opportunity to develop these new function on top while simultaneously testing them with a variety of model outputs.
Functionality for (very related) vertical grid transformation has happened mostly at Plotting ocean variables in density coordinates (using xhistogram), but this could be a fit for this more technicsl project too.
I am unsure if I should propose this as a seperate project, since it will surely benefit other proposals as well. @matt-long, @rabernat, do you think it would make sense to split out the more techincal aspects?