GCM evaluation along the lateral boundaries of the CORDEX domains

[SwenBrands]

The idea is to compare historical GCM runs along the lateral boundaries of the different regional domains used in CORDEX against a reference reanalysis, a as was done in, e.g., http://dx.doi.org/10.1007/s00382-013-1742-8. The latitude-longitude coordinates of the domain boundaries can be retrieved from @larsbuntemeyer:

https://github.com/WCRP-CORDEX/domain-tables/blob/main/CORDEX-CMIP6_boundaries.csv

Abbreviations in the table are as follows: tlc = top left corner, trc = top right corner, blc = bottom left corner, brc = bottom right corner, cnb = center of the northern boundary, ceb = center of the eastern boundary, csb = center of the southern boundary, cwb = center of the western boundary, cpd = center point of the domain:

TLC----CNB----TRC
 |             | 
CWB    CPD    CEB
 |             |
BLC----CSB----BRC

This file will be updated for CORDEX-CMIP7. The evaluation focuses on the atmospheric variables used to drive the RCMs, i.e. u, v, z, hus, ta on multiple pressure levels, ps at the land surface, as well as tos at the ocean surface. Bilinear interpolation can be applied to interpolate the GCM data to the aforementioned coordinates, taking into account the land-sea mask for ps and tos. The mean error (bias) in the year-round monthly-mean data, averaged over the 9 coordinates of each CORDEX domain, is a good error metric to begin with. 1979-2021 is a suitable reference period that covers the satellite era and is long enough to at reduce the effects of internal variability on the error results.