CESM Models

What's New in CESM1.2.0 - Science

The CESM1.2 release has numerous new key features among which are the addition of CLM4.5, new science changes to CAM5 running with the CAM-SE dynamical core, and new scripting infrastructure for the generation of component sets, grids and model testing.

Additional information regarding these updates is also available in the CESM User's Guide and in the individual model component documentation.


CAM5.3 includes modifications and updates for the spectral element dynamical (SE) core. These include a change from an Eulerian to a Lagrangian calculation for vertical advection. The updated version of the Morrison Gettelman microphysics is now available (MG1.5) with fixes for droplet activation and a major code refactoring. The ability to run a prescribed version of the Modal Aerosol Modal (MAM3) is also available. Finally the capability to significantly reduce default history file size, retaining only those fields needed for the AMWG diagnostics, is included.


The new features available in CAM-Chem in this release include:

All these are released to give users access to these new capabilities. Only limited evaluation has been performed.


Functional updates for WACCM include:


For more details on the changes made in CESM1.2.0, see the "What's new in CESM1.2.0" section of the CISM documentation.


CLM4.5 incorporates a broad set of changes throughout the model including a revised photosynthesis scheme, improved cold region hydrology and optional VIC-based hydrology, prognostic wetland distribution, a new snow cover fraction parameterization, a new lake model, new crop model features such as fertilization and grain fill, and multiple urban classes. Biogeochemistry changes include the introduction of a Century-like vertically resolved soil biogeochemistry scheme with revised denitrification and biological fixation processes as well as a methane emissions model, a revised fire model including anthropogenic triggers and suppression, and 13C and 14C isotope fractionation.

Important Note - CLM4.5 has been evaluated for "CLM offline mode" (I compsets), but has NOT been evaluated or scientifically validated when coupled to the other models.

Data Models


Updates to the POP ocean model include:



CESM1.2.0 introduces a new WAV model to CESM with initial support of just the stub and dead versions for this release.