AMWG CAM Development Activities


This page is intended to be a summary of the Atmosphere Model Working Group (AMWG) activities in developing the CESM Community Atmosphere Model (CAM). CAM4 was released as part of the CCSM4 release in June 2010 with the following notable improvements and IPCC AR5 simulations. No further core development activities will be done with CAM4. All future development will be done using CAM5. Development activities are primarily driven by the CAM Strategic Plan. Activities are supported from a broad range of sources including, NCAR(NSF), DOE, NASA, NOAA, EaSM awards and CPT awards in addition to multiple UCAR and other University-based activities.

Details of CAM specific development activities are listed below, but a number of projects are also relevent to development within other working groups including CAM-chem through the Chemistry-Climate Working Group (Chem-ClimWG), WACCM and WACCMX through the Whole Atmosphere Working Group (WAWG) and the CISL IMAGe Data Assimilation Research Testbed (DART) using CAM.

Some simulation links are password protected, but access to active model developers can be granted by contacting the AMWG community liaison.


CAM5 was released in June 2010 as part of the Community Earth System Model, version 1 (CESM) release with a number of signficant notable improvements. In summary the physics parameterization changes compared to CAM4 are:

  • The 2-moment Morrison Gettelman (MG) bulk stratiform microphysics scheme (Morrison and Gettelman 2008).
  • The University of Washington (UW) planetary boundary layer/moist turbulence scheme (Park and Bretherton 2009).
  • The University of Washington (UW) shallow convection scheme (Park and Bretherton 2009).
  • An improved consistancy cloud macrophysics scheme (presentation, Sungsu Park).
  • The Rapid Radiative Transfer Model for GCMs (RRTMG) radiation scheme (Mike Iacono and Andrew Conley).
  • The 3-mode prognostic Modal Aerosol Model (MAM3) scheme with revised droplet activation (presentation, Xiaohong Liu and Steve Ghan).

The inclusion of new physics in CAM5 allows new research into process interactions associated with cloud-aerosol-radiation indirect effects; a major source of IPCC uncertainty in the radiative impacts of the 20th century climate. Fully coupled pre-industrial and 20th century simulations performed using CAM5.0 can be found here (password required).

As with CAM4, the Spectral Element (CAM-SE) dynamical core option based on HOMME is also available in the CAM5 release.

CAM5.1 Release

CAM5.1 will be released prior to the 2011 CESM Workshop in June. This version of the model in its default configuration will be used for all CESM (CAM5) IPCC AR5 simulations using the CMIP5 experiment protocol. It includes a number of changes and signficant bug fixes compared to CAM5 including:

  • Modifications to correct the effective radiative radius of precipitating snow crystals which required minor climate retuning
  • To be consistant with CESM(CAM4) CMIP5 experiments the prognostic carbon-nitrogen cycle is turned on in the land model (CLM4).
  • Tuned coupled configuration will be available for both finite volume, 1 degree and 2 degree resolutions (simulations).

CAM5.2 Release Plans

A number of changes are planned for the release of CAM5.2 in the Fall of 2011. This release is intended to form a base model for all other CESM components to continue their next stages of development. The current plan is to make the following major changes to the CAM5.1 release:

  • A prescribed version of the Modal Aerosol Model (MAM3) will be the default option
  • The HOMME/CAM-SE dynamical core will be the default option (at least for equivalents for current FV resolutions of 1 degree and finer).

Current Simulations

Current CESM(CAM5.1) simulations are focused on completing a large fraction of the IPCC AR5 suite of experiements at 1 degree and 2 degree resolutions.

Simulations completed (diagnostics):

  • 1 degree 1850 control
  • 1 degree SOM 1xCO2 and 2xCO2
  • 1 degree 20th century ensemble 1
  • 1 degree AMIP (1979-2006)

Simulations ongoing

  • 2 degree 1850 control
  • 2 degree 20th century (2 ensembles)
  • 1 degree 1850 (CAM4-SE) control

Simulations to be completed

  • 1 degree 20th century ensemble 3
  • 2 degree 20th century w/ aerosol emission evolution only
  • 2 degree 20th century w/o aerosol emission evolution
  • 1 degree RCP8.5
  • 1 degree RCP4.5
  • 2 degree 20th century
  • 2 degree AMIP (1979-2006)
  • 2 degree SOM 1xCO2 and 2xCO2

Simulations proposed

  • 1 degree AMIP (CAM5-SE)
  • 2 degree 1850 control (prescribed aerosols)

Model Infrastructure and Major Projects

CAM development code maintenance and implementation for both CAM and CESM is carried out by the CESM software engineering group (CSEG). Ongoing and upcoming general model development and infrastructure updates relevant to CAM are listed below.

  • Represntative Concentration Pathways (RCPs) emissions are being generated for future scenario runs with CAM5 using prognsotics MAM3 aerosols
  • The CLM grid is being changed to the CAM-SE cubed-sphere grid for co-location of grid boxes with the atmosphere

Major Projects

A brief description of major, cross-component model development activities is listed below

CSSEF Climate Science for Sustainable Energy Future (CSSEF) is a DOE-funded cross-lab+NCAR effort aimed at providing next generation earth system, modeling capability within the context of observational data utilization and Uncertainty Quantification (UQ). Activities for next generation CAM development can be found here. (Project lead: Dave Bader, LLNL; Atmosphere lead: Steve Klein, LLNL)

Physics Development

Community development activities related to the improvement of the physical parameterizations (convection, boundary layer, cloud microphysics, cloud macrophysics, radiation and gravity wave drag) are detailed below.

UNICON A unified convection scheme for CAM to replaces separate shallow and deep schemes (presentation; Sungsu Park, NCAR)

CAM-SP Integrating the CAM-SP (superparameterized CAM) into the CAM framework to assess aerosol indirect impacts and CMIP5 experiments. CAM-SP replaced most of the moist physics parameterizations in CAM with a small domain (usually 2D) Cloud Resolving Model (CRM-SAM) at each prid-point (EaSM project1, project2; Andrew Gettelman and Sungsu Park, NCAR)

CAM-CLUBB Implement a multi-variate PDF based moist turbulence and cloud macrophysics scheme based on the Cloud Layers Unified By Binormals (CLUBB) into CAM as part of a Climate Process Team (Andrew Gettelman, Pete Bogenschutz and Hugh Morrison, NCAR)

CAM-PDFcloud a PDF-based cloud macrophysics scheme implemented into CAM (presentation; Peter Caldwell and Steve Klein, LLNL; Sungsu Park, NCAR and Chris Bretherton, UW)

Convective Microphysics An implimentation of the Morrison Gettelman 2-moment microphysics into the Zhang-McFarlane deep convection parameterization (paper; Guang Zhang and Xiaoliang Song, SCRIPPS)

Convective Organization Development of a convective organization augmentation to the UW shallow convection scheme in CAM (paper; Brian Mapes, U. Miami and Rich Neale, NCAR)

Stochastic Backscatter Implementaion of small-scale energy reintroduction at larger scales (Judith Berner, NCAR)

Dynamics Development

Community development activities related to improvemed performance of the dynamical core are detailed below.

CAM-SE Integrating the HOMME spectral-element dynamical core into CAM (presentation; Mark Taylor, Sandia and Saroj Mishra, NCAR/CU)

CAM-MPAS Integrating the Model for Prediction Across Scales (MPAS) dynmical core into CAM (presentation; Joe Klemp, Bill Skamarock and Art Mirin)

CAM-FV3 Integrating the finite volume dynamical core on a cubed sphere grid (Christine Jablonowski, UMich; Will Sawyer, U. and Art Mirin, LLNL)

CAM-EULAG Integrating the EULerian (flux form), or a LAGrangian (advective form) modelling framework (EULAG) into CESM (presentation; Bill Gutowski, Iowa State; Babatunde Abiodun, U. Cape Town; and Piotr Smolarkiewicz, NCAR)

CSLAM The Conservative Semi-LAgrangian Multi-tracer scheme (CSLAM) is being tested and implemented in HOMME to provide multiple tracer scalability (presentation; Peter Lauritzen).

Model Diagnosis

Standard diagnosis of CAM development runs involves using the AMWG diagnostic package to analyze the simulation performance. Determining whether a simulation is acceptable or not will depend on the outcome of the AMWG standard analysis procedures. Beyond the standard analysis there are a number of diagnostic projects aimed at addressing specific aspects of CAM simulations:

Cloud Simulators The CFMIP Observational Simulator Package (COSP) has been implemented into the CAM code and is available for to use in both CAM4 and CAM5 to better diagnose model cloud fields based on native, remotely sensed retrieval algorithms (NCAR: Jen Kay; UW: Ben Hillman; LLNL: Yuying Zhang, Jim Boyle and Steve Klein)

CAM-CAPT The CAM implementation the Cloud Associated Paramaterization Testbed (CAPT) is enabling an assessment of the contribution of fast physical processes to the mean climate errors in CAM (NCAR: Dave Williamson, Jerry Olson, Brian Medeiros and Cecile Hannay; LLNL: Steve Klein, Jim Boyle, Shaocheng Xie; CIRES: Robert Pincus; UW: Roger Marchand)

Hurricane Analysis Tracking the performance of high resolutions CAM simulations in producing credible hurricane statistics (Julio Bacmeister)

Identifying and Addressing Systematic Errors

Systematic errors that are currently being addressed and have persisted since CAM3 include

  • Twin ITCZ in the East Pacific
  • Excessive northern ITCZ in the East Pacific

East Pacific/Double ITCZ CAPT forecast activities examining how ITCZ errors develop (David Williamson and Rich Neale)

US Summer Time Rainfall Examining the source of summertime seasonal and diurnal rainfall biases (Mitch Moncrieff and Rich Neale)

CESM Project

The Community Earth System Model (CESM) is a fully-coupled, global climate model that provides state-of-the-art computer simulations of the Earth's past, present, and future climate states.

CESM is sponsored by the National Science Foundation (NSF) and the U.S. Department of Energy (DOE). Administration of the CESM is maintained by the Climate and Global Dynamics Division (CGD) at the National Center for Atmospheric Research (NCAR).


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