Climate Modeling Section

This year, the Climate Modeling Section in collaboration with the Atmospheric Modeling Working Group released a major new release of the NCAR Community Atmosphere Model called CAM2. This model incorporates improvements in the physics, dynamics, and numerical formulations developed in partnership with colleagues at universities and national laboratories. Some of the major enhancements include better treatments of cloud condensate, radiation processes, and sea ice. Through NCAR's ongoing collaboration with NASA, CAM2 incorporates a new formulation for atmospheric circulation known as the Finite Volume dynamical core. CAM2 will be the atmospheric component of the coupled climate models used by NCAR in upcoming national and international climate assessments.

This figure shows the outgoing longwave radiation (OLR) simulated by the new Community Atmosphere Model (CAM2, left panel) and measured by the NASA Earth Radiation Budget Satellite (ERBS, right panel). The region is the tropical Pacific between 100E and 80W. The OLR has been averaged between 5N and 5S. The mean value for the period 1985-1999 has been subtracted to give anomalies, i.e. differences relative to the long term mean. CAM2 was integrated using observed sea surface temperatures.

Positive anomalies east (to the right of) the date line show periods when convection is suppressed relative to the long-term mean. These roughly correspond to La Ninas during the observational record. Negative anomalies east of the date line show period of enhanced convection corresponding to El Ninos. Notice that the anomalies east and west of the dateline generally have opposite sign, corresponding to the dipole in convective cloud cover driven by ENSO.

The figure shows that the new CAM is able to reproduce the tropical fluctuations in OLR with considerable fidelity in their timing, strength, and geographical distribution. This is a marked improvement compared to the previous version of CAM.