A new flexible coupler for earth system modeling developed for CCSM4 and CESM1

The Community Climate System Model (CCSM) has been developed over the last decade, and it is used to understand past, present, and future climates. The latest versions of the model, CCSM4 and CESM1, contain totally new coupling capabilities in the CPL7 coupler that permit additional flexibility and extensibility to address the challenges involved in earth system modeling. The CPL7 coupling architecture takes a completely new approach with respect to the high-level design of the system. CCSM4 now contains a top-level driver that calls model component initialize, run, and finalize methods through specified interfaces. The top-level driver allows the model components to be placed on relatively arbitrary hardware processor layouts and run sequentially, concurrently, or mixed. Improvements have been made to the memory and performance scaling of the coupler to support much higher resolution configurations. CCSM4 scales better to higher processor counts, and has the ability to handle global resolutions up to one-tenth of a degree.