Regridding standards

I refer to the regridding standards documented as "Observations and GCMs should be regridded to RCM/CCAM grid using conservative area weighted remapping" on https://github.com/AusClimateService/ccam-evaluation/blob/main/evaluation_standards.md.

We agree that conservative method is suitable for upscaling.

For downscaling, it is less clear, whether NN, bilinear or conservative. The use cases are evaluation of mean states, climate indicators, and added-value analyses. I assume using the implementations given by xesmf.Regridder, https://xesmf.readthedocs.io/en/latest/notebooks/Compare_algorithms.html

Do we also want to worry about any height correction (to temperature for instance) using lapse rates? Which can be messy.

I raise this issue for discussion and reaching agreement.

Read evaluation_standards.md and compare the xesmf.Regridder algorithms described in the linked documentation for the stated upscaling, downscaling, and evaluation use cases. The work is complete when the project agrees on the remapping methods and any height-correction policy, then records that decision in the standards document.

Written by the indexing model from the issue text.