Development of the Community Climate System Model-2
Maurice L. Blackmon
Climate and Global Dynamics Division
National Center for Atmospheric Research
Boulder, Colorado 80307, USA
The original Climate System Model (CSM) was released for use five years ago. Equilibrium runs were performed for today's climate, for the climate of the 19th century, and several projections of climate change for the 21st Century. However, diagnostic work using CSM data has uncovered flaws in all components of the model. These include low values of atmospheric variability in the tropics, low values of ocean currents and variability in the tropics, temperature biases over land surfaces in midlatitudes and ice concentrations higher than the observed values. In addition, scientists in the United States are now using microprocessor-based, distributed-shared-memory machines, so the codes used in the CSM, which ran efficiently on vector supercomputers, are being rewritten in order to increase performance on the new machines.
While the configuration of our next model, the Community Climate System Model-2 (CCSM-2), is not yet fixed, some of the improved model components and model physics that will be included in CCSM-2 have been identified. I will discuss what is likely to be included in each model component and show how it has improved the simulation characteristics of each component.
I will also discuss new features that will be included in CCSM-2, either in its standard version, or in the research version that will evolve toward CCSM-3. These include river runoff, improved land hydrology, ecosystem dynamics, an interactive biogeochemistry component, and a middle atmosphere component.
