CESM2 contains several subversions as described on the CESM2 Release Webpage. CESM2.0 and CESM2.1 are consistent with CMIP6 simulations, while CESM2.2 contains a number of updates that will give different results from previous versions. CESM2.2 is a "functional" release, and not all available compsets and configurations have been scientifically validated. When building some combinations of resolution and compsets you may need to include the switch "--run-unsupported" when creating a case. The default chemical mechanism for CAM-chem in CESM2 is the MOZART-TS1 chemistry (Emmons et al., 2020) with MAM4 aerosols and a VBS-SOA scheme (Tilmes et al., 2019).
CESM2.2 contains MUSICA-V0. CESM2.2 also includes an updated scavenging of aerosols in convective clouds. The MOZART-TS2 chemical mechanism (Schwantes et al., 2020) is available. Both MOZART-TS1 and -TS2 now include the NOx-dependent VBS-SOA scheme described in Jo et al. (2020).
The definitions of CESM compsets (component sets, i.e., configurations) can be found here: http://www.cesm.ucar.edu/models/cesm2/cesm/compsets.html. Current CAM-chem compsets start with "FC". More information on the CESM2.2 CAM-chem compsets is available on the MUSICA-V0 wiki. Compsets that include "ts2" use the MOZART-TS2 chemical mechanism published in Schwantes et al. (2020). Compsets with "nudged" use the physics-side nudging, as described in the CAM User's Guide. Spectral Element resolutions are now available: "ne30" is approximately 1-deg resolution, ne30pg3 is approximately 1-degree with CSLAM (Conservative Semi-Lagrangian multi-tracer transport scheme). More information on supported grids is on the CESM2 grids webpage.