The National Center for Atmospheric Research (NCAR)

• The Kasahara/Washington Models (NCAR 1-3)
• NCAR Community Climate Model
  • CCM-0A
  • CCM-0B: A Combined Forecast and Climate Simulation Model
  • CCM-1
• Current NCAR Models
• References

The National Center for Atmospheric Research, established in 1960, initiated a GCM effort in 1964 under Akira Kasahara and Warren Washington.

Two different model series were eventually constructed, designated here as NCAR 1-3 and CCM 0-2.

The Kasahara/Washington Models (NCAR 1-3)

The first-generation NCAR GCM was developed starting in 1964, with first publication in 1967. It was a simple 2-layer global model with a 5° horizontal resolution.

The second-generation model, completed around 1970, added a great deal of flexibility. The basic model had a 5° horizontal, 6-layer resolution, but it could also be run at resolutions as fine as 0.625° horizontal over a limited domain, with up to 24 vertical layers.

NCAR 3, finished about 1973, also allowed multiple resolutions, including a user-specifiable vertical increment. The most significant changes, however, involved improved finite-difference schemes.

The Kasahara/Washington group focused a great deal of attention on numerical schemes for finite-difference approximations. In addition, a great deal of work was done on problems of computational error arising from truncation.[1]

NCAR Community Climate Model

In the latter part of the 1970s, the National Center for Atmospheric Research gradually abandoned the Kasahara/Washington model. In its place, NCAR developed a Community Climate Model (CCM), intended to serve not only modelers working at NCAR, but the large constituency of affiliated universities associated with NCAR's parent organization, the University Corporation for Atmospheric Research. The Community Climate Model was initially based on the Australian Numerical Meteorological Research Center model and an early version of the ECMWF model. It also incorporated elements of the GFDL models.

The NCAR CCM series of models was especially important because of the relatively large community of researchers who were able to use it. Versions of the model were adopted by a number of other groups in the late 1980s. This was made possible by NCAR's strong focus on documentation and modularity. User manuals and code documentation were made available for all elements of the models starting with CCM-0B.

CCM-0A

The initial version of the Community Climate Model was based on the spectral model of the Australian Numerical Meteorological Research Centre. One member of the ANMRC team (K. Puri) brought the model to NCAR during an extended visit. Later, it was extensively revised.[2]

CCM-0B: A Combined Forecast and Climate Simulation Model

A second version of the Community Climate Model was developed in 1981. This model's guiding purpose was "NCAR's decision to utilize the same basic code for global forecast studies (both medium- and long-range) and for climate simulation. Economy and increased efficiency could then be achieved by documenting and maintaining only one set of codes. Changes from one application to the other could be relatively straightforward in a model with modular design. The use of one basic model for both forecasting and climate studies has potential scientific value since a major part of long-range (one- to two-week) forecast errors is due to the drift toward a model climate which differs from that of the atmosphere. Thus, improvements in the climate aspects of the model should lead to improvements in forecasts."[3]

CCM-0B was designed to include the best elements of other existing models. Initial code for CCM-0B came from an early version of the European Center for Medium Range Weather Forecasts model. Physical parameterizations, including the radiation and cloud routines of Ramanathan, and numerical approximations were added from CCM-0A.[4] Energy balance and flux prescriptions from the early GFDL models were incorporated, while the finite difference scheme was derived from the Australian spectral model that was the basis for CCM-0A.[5]

CCM-1

CCM-1 evolved from CCM-0B in the mid-1980s. The primary differences were changed parameterizations, new horizontal and vertical diffusion schemes, and changes to moisture adjustment and condensation schemes.

Current NCAR Models

• CCM-2 (1992)
• CCM-3

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References

[1] A. Kasahara and W.M. Washington, "NCAR Global General Circulation Model of the Atmosphere," Monthly Weather Review, July 1967, 389-402.

[2] W. Bourke et al., "Global Modeling of Atmospheric Flow by Spectral Methods," in General Circulation Models of the Atmosphere, Methods in Computational Physics: Advances in Research and Applications (San Francisco: Academic Press, 1977), 267-324.

[3] D.L. Williamson et al., "Description of NCAR Community Climate Model (CCM1)," (National Center for Atmospheric Research, 1987).

[4] V. Ramanathan et al., "The Response of a Spectral General Circulation Model to Refinements in Radiative Processes," Journal of Atmospheric Sciences 40 (1983): 605-630.

[5] D.L. Williamson et al., "Description of NCAR Community Climate Model (CCM1)," (National Center for Atmospheric Reasearch, 1987).