This documentation describes tools and procedures for creating paleoclimate simulations using the NCAR CESM1 model. Using the CESM1 model for paleoclimate modeling requires complex, multi-step modifications to the input and forcing files used by the model, particularly for Deep Time simulations where continental configurations have changed. These tools are developed on the computing resources at the National Center for Atmospheric Research (NCAR) and we strive to keep pace with the current version of the CESM1 model. Researchers may need to modify these procedures to accommodate the version of the CESM1 model they are using, or for the computer resources available on their home machines. To gain more understanding about the CESM1 component models and input files, see the CESM1 documentation http://www2.cesm.ucar.edu/.
This document describes the procedures for creating a CESM1 paleoclimate simulation in the fully coupled (all active components) configuration. CESM1(CAM5/CLM4.0) is the default configuration for CESM1. IPCC/CCSM4.0 simulations are equivalent to running CESM1.0 (CAM4/CLM4.0) (Release code cesm1_0_5).
Throughout this User’s Guide we differentiate between CESM1 for Quaternary and CESM1 for Deep Time. The procedures required to create near-modern (e.g., Quaternary, Pliocene) and Deep-Time (pre-Quaternary) model simulations are similar, but important differences exist. In near-modern simulations, the continents are in their present-day positions, the land/sea masks do not require significant modification, and modelers can often use default mapping and grid files. In addition, Quaternary modelers are often able to use existing pre-industrial forcing files to drive the model. By contrast, deep-time simulations include drastic modifications to the land/sea mask, which requires embedding the ocean bathymetry onto the ocean grid, creating new coupler mapping files, specifying ocean and atmospheric initial conditions and scientifically consistent model forcing. In addition, the modeler is responsible for providing the orographic/bathymetric maps for their geologic period of interest.