Randall95 Randall, D.A., D. Dazlich, L. Fowler, D.-M. Pan, P. Sellers, and C.-H. Chen, 1995: The CSU AMIP runs. Abstracts of the First International AMIP Scientific Conference, Monterey, California, 90.

The Colorado State University (CSU) atmospheric general circulation model (GCM) completed its first AMIP simulation (CSU91) in 1991. A second simulation (CSU94) was conducted in 1994, after three major changes had been made to the model, namely:
 
  • The cumulus parameterization was revised to make use of a prognostic cumulus kinetic energy;

    •  
  • SiB2, the second-generation version of the land surface parameterization developed by P. Sellers and colleagues, was installed in the GCM;

    •  
  • The stratiform cloud microphysics parameterization developed by L. Fowler and colleagues was adopted.
This first round of changes to the model led to improvements in the simulation of the Earth's radiation budget and cloudiness, as surface air temperature, snow cover, the Indian summer monsoon circulation, and the precipitation rate.

A third AMIP run (CSU95) is now being conducted. This version of the model includes a gravity wave drag parameterization developed by Kim and Arakawa at UCLA, and also a simple convective downdraft parameterization developed at CSU by C.-H. Chen and D. Randall. In addition, for AMIP95 the top of the model has been raised to the 1 mb level, whereas in AMIP91 and AMIP94 it had been at the 50 mb level. Preliminary results indicate that CSU95 has more realistic zonal winds, precipitation rate, and tropical thermodynamic structure. The simulated Indian summer monsoon has also improved further.