Add distinctive look for AMIP type variable resolution models

[jesusff]

As in #75 , we should add some distinctive look to help users identify models driven only by SST and sea ice, as these can behave quite differently to RCMs or GCM with atmospheric nudging, which have their circulation constrained. This is allowed by the CORDEX experiment design:

Variable resolution global climate models (VR-GCMs) that follow the CORDEX protocol for a given domain (e.g., resolution, etc.) may also contribute to that domain. In this case, the use of atmospheric nudging to incorporate information from the driving GCMs’ atmosphere is encouraged; thus, making the VR-GCMs more comparable to the limited area RCMs. The inclusion of VR-GCMs adds to the overall diversity of the CORDEX ensembles, which provides some advantages, but the methodological differences when compared to limited area RCMs should be considered when combining the VR-GCMs and RCMs in an ensemble. There are many ways that variable resolution is achieved and it is up to the modelling groups
to determine an optimal configuration.

[jesusff]

This is the case e.g. for some versions of CCAM (WCRP-CORDEX/cordex-cmip6-cv#126, WCRP-CORDEX/cordex-cmip6-cv#128)

@sdesrosiers1989 wrote:

CCAM is a stretched grid global model [...] using bias-corrected SSTs and sea ice plus CMIP6 radiative forcing. Basically an AMIP style experiment.

[jesusff]

I wonder about the ocean coupled versions (CCAMoc; WCRP-CORDEX/cordex-cmip6-cv#127), as these produce their own SST and sea ice. Are these nudged towards the driving GCM? which fields?

[sdesrosiers1989]

For our ocean coupled versions, spectral nudging was applied to the host model SSTs. We used the same type of nudging as CCAM-ACS did for their ERA5 runs.

https://journals.ametsoc.org/view/journals/apme/63/9/JAMC-D-24-0004.1.xml?rskey=1p0Pze&result=1

[jesusff]

Thank you for the details!