The COLA Atmosphere-Biosphere General Circulation Model (ABGCM) has evolved from its single thread NCEP based dynamical core framework (Version 1.12) described in Kinter et al. (1997) to a multithreaded NCAR based dynamical core (Version 2.2). Most physical processes and options from the V1.12 code were retained, however indexing in both the vertical (now always top-down instead of usually bottom-up) and the latitudinal (now South-to-North instead of North-to-South) directions have been changed to be consistent with the NCAR dynamical core. Significant revisions have been made to the land surface process calculations. These are described in Dirmeyer and Zeng (1997) and Dirmeyer and Zeng (1999). The NCAR dynamical core used is based on a Fortran 90 version of the CCM3.2 AGCM described in Kiehl et al. (1996) and Acker et al. (1996). The core, while spectrally based, uses either spectral moisture transport or semi-Lagrange moisture transport. The time step cycling also differs with adjustment physics (large scale and convective moist processes) being done first and flux based physics (planetary boundary layer, radiation, land and ocean surface processes) done second. The actual cycle of calculations: adjustment physics, flux physics, time stepping (including advection and horizontal diffusion) and time filtering remains the same as V1.12, but the now cycle begins with the adjustment physics instead of the flux physics and no Fourier-Legendre transform takes place between the two physics calculation branches.

While the physical process calculations have been reindexed, the original spectral, horizontal and vertical parameters have been retained. A table shows their correspondence with the NCAR parameters. Similarly the original model clock and most of the I/O have been retained from V1.12. This permits continued use of many model run options from V1.12 and the use of existing software for input data set preparation and model output post processing. As a result, many of the files used to run the model and those created by the model are the same except for the indexing changes. These files are discussed in the Version 2 files document.

Running the model first requires understanding the model diagnostics system in order to select what model diagnostics are needed for a given experiment and to learn the model output data arrangement. This is described in the model diagnostics document.

Once the model data sets and diagnostic tables have been prepared, the model NAMELIST parameters can be set to determine the model run length, time stepping, physics options and other options. These are all described in the model NAMELIST document.

Some examples of model run scripts can be seen in the model scripts document.


Acker, T. L., L. E. Buja, J. M. Rosinski and J. E. Truesdale (1996): Users's Guide to the NCAR CCM3. NCAR/TN-421+IA.

Dirmeyer, P. A. and F. Zeng (1997): A Two Dimensional Implementation of the Simple Biosphere (SiB) Model. COLA Technical Report No. 48.

Dirmeyer, P. A. and F. Zeng (1999): An update to the distribution and treatment of vegetation and soil properties in SSiB. COLA Technical Report No. 78.  

Kiehl, J. T., J. J. Hack, G. B. Bonan, B. A. Boville, B. P. Briegleb, D. L. Williamson and P. J. Rasch (1996): Description of the NCAR Community Climate Model (CCM3). NCAR/TN-420+STR.

Kinter, J. L. III, D. DeWitt, P. A. Dirmeyer, M. J. Fennessy, B. P. Kirtman, L. Marx, E. K. Schneider, J. Shukla and D. M. Straus (1997): The COLA Atmosphere-Biosphere General Circulation model Volume 1: Formulation. COLA Technical Report No. 51.