Model Developments

The following developments for CAM-chem (including the Workhorse Model: Mid-Top 93L (80km) and Low-Top 58L (40km) (ne30pg3)) are listed below.

Detailed development plans: Wiki Page

Updates planned for CESM3:

  • Default configuration will be Spectral Element dynamical core with a cubed sphere grid at approximately 1-degree resolution (ne30pg3)
  • Introduction of stratospheric aerosol (MAM5)
  • New dust scheme (Leung et al., 2023)
  • Chemistry mechanism naming: T1S etc. -- numbers are associated with the tropospheric mechanism because this updates frequently. Workhorse chemistry (for CMIP7) will be T4S. More detail on different mechanisms here: https://www2.acom.ucar.edu/gcm/mozart
  • Updated vertical resolution: more layers in the PBL and UT/LS
    • Low-Top = 58 layers to ~40 km
    • Mid-Top = 93 layers to ~80 km
    • High Top (WACCM) = 135 layers to ~140 km

Chemistry configuration options in CESM3

Updates implemented but not validated:

  • Chemistry: Troposphere + Stratosphere (TS1.2) (CAM Issue #558)
  • New aerosol model: MAM5 (MAM4 + 1 mode for stratospheric sulfate) for all CESM configuration (CAM Issue #663, #664)
  • Optional Upper boundary conditions for the low top L58 model  (CAM Issue #533)
  • Updated Soil NOx emissions (CTSM Issue #1952)
  • Simple chemistry (for CAM7)  with updated SOA parameterization to support tropospheric aerosol formation (MAM4) (CAM Issue #727)
  • T4 chemistry mechanism, simplified from T1 to be used for longer climate-scale simulations such as CMIP7
  • Online DMS emissions based on Online Air-Sea Interface for Soluble  Species (OASISS) -> all CESM compsets (CAM, CAM-chem, WACCM)
  • HEMCO Emission Component (CAM Issue #560)
  • New dust emission scheme in CTSM (CAM Issue #651)

Updates to be added

  • Additional online ocean (acetaldehyde etc.) emissions based on OASISS
  • New photolysis scheme (TUV-x) (https://github.com/NCAR/tuv-x)
  • Marine Organic Aerosol Emissions (CAM Issue #531)
  • MEGAN3 biogenic emissions (CTSM Issue #1323)
  • Very Short Lived (VSL) halogen chemistry and interactive methane emissions

Page last updated: July 2025