This User's Guide describes the overall design of the most recent version of the NCAR Community Climate Model, CCM2. In addition to in-depth information about running the CCM2 model code, the User's Guide gives a detailed description of the code organization and data structures so that CCM2 can be modified by users as mandated by their particular research requirements. Section I of this report, titled "Using CCM2," presents sample scripts for executing the Model, describes the input parameters, and provides information about input datasets, output file formats, and samples of output from a Model integration. Section II, "CCM2 Internals," gives a detailed description of the Model control and data flow. The various data structures are described, along with detailed control flow and file management information, and multitasking capabilities. This section concludes with tips on modifying the basic code, adding and/or changing physical parameterizations, basic trouble-shooting techniques and a description of the "plug-compatible" coding standard adopted for CCM2.
