Multi-Scale Chemistry Modeling (MUSICA)

Group Lead: Dan Marsh

Focus 3: Development of a Unified Community Multi-scale Modeling Infrastructure for Chemistry and Aerosols (MUSICA).

ACOM builds, critically evaluates and applies process, regional- and global-scale models that address atmospheric chemistry research questions, with a focus on couplings between different components of the Earth system (water cycle, biosphere, cryosphere). This section provides the necessary modeling tools to address the following scientific challenges.

Global Chemistry Modeling

ACOM leads the development of the representation of chemistry in two components of the Community Earth System Model (CESM):

    • CAM-Chem: Community Atmosphere Model with Chemistry
    • WACCM: Whole Atmosphere Community Climate Model

These models are developed under the general direction of the CESM Chemistry-Climate Working Group and Whole Atmosphere Working Group.

CAM-Chem and the Whole-Atmosphere Community Climate Model (WACCM)  are versions of the NCAR Community Earth System Model that couple the Community Atmosphere Model with chemistry based on MOZART.  Both CAM-Chem and WACCM can operate in two modes; 'free-running' with fully coupled chemistry and climate, or with dynamics contrained to analyzed meteorological fields (e.g., GEOS-5 or MERRA).  WACCM has a model top that extends to ~140 km and includes a stratospheric/mesospheric chemical mechanism with both neutral and ionized constituents.  WACCM is particularly suited for studies from the upper troposphere through the mesosphere.  CAM-chem is suitable for studies of air quality and chemistry-climate interactions focused on the troposphere.

Assessments and Intercomparisons

ACOM participates in numerous model assessments and model intercomparison projects:


Scientific Themes



  • CESM2 has been released and will be used for CMIP6 simulations.


Regional Modeling 

  • WRF-CHEM: Weather and Research Forecasting model with Chemistry


Process Modeling 

    • BOXMOX: Box Model
    • DICE-Africa: Diffuse and Inefficient Combustion Emissions in Africa
    • FINN: Fire INventory from NCAR
    • GECKO-A: Generator of Explicit Chemistry and Kinetics of Organics in the Atmosphere
    • NCARMM: the NCAR Master Mechanism chemistry box model
    • TUV: Tropospheric Ultraviolet and Visible radiation model




ACOM | Atmospheric Chemistry Observations & Modeling