Add CMORized AeroNET aerosol optical depth observations to the Tier 3 category

[catherinehardacre]

Issue #2775 adds support for an aerosol optical depth climatology metrics to the AutoAssess replacement. For the recipe and and diagnostic to be tested in ESMValTool the AeroNET AOD observations must be CMORized and added to an ESMValTool observational data base.

The work in this issue will CMORize the AeroNET AOD climatologies developed for #2775 and add support for these into ESMValTool. The CMORIzed observations will be classified as Tier 3 initially because further work to develop automatic download scripts, pre-processing scripts and CMORizers will be required.

This work is assigned to me, catherinehardacre.

[bouweandela]

The deadline for including new work in v2.9 has passed, so I'm removing this issue from the milestone. Please add it to the next milestone if you plan to include this in the next release.

[zklaus]

We're almost there with #3227, but won't make it into 2.10.

[mo-gill]

Hi, we are currently working on the ESMValTool release for v2.11.0. We're wondering if you'd be able to finalise this issue by the end of next week (Friday 10th May).

Otherwise, please let us know, and we'll move it into the next milestone for you 🙂