CESM1 Paleo Users Guide

Introduction

A brief note to users ... 

The Community Earth System Model (CESM1) is a coupled climate model for simulating the earth's climate system. Composed of four separate models simultaneously simulating the earth's atmosphere, ocean, land surface and sea-ice, and one central coupler component, the CESM allows researchers to conduct fundamental research into the earth's past, present and future climate states. Please see the brief overview of the notable model improvements.

The CESM and its component models have been invaluable tools for the national and international research communities.  These models have been used by researchers worldwide, starting with the first version CSM1, to explore problems of both greenhouse and icehouse past climates.  They have been shown to be adaptable for both deep-time paleoclimate applications, when the continental configurations were much different from present, to the more near-term past climates of the glacial-interglacial cycles of the last million years.  Over 60 research articles using versions of CESM for studying past climates have been published by the community.   Low-resolution versions of CESM1 have been developed and supported to allow paleoclimate researchers to integrate the model for thousands and even tens of thousands of years.  This document outlines the procedures for setting up paleoclimate simulations with CESM1, released in 2010.  The science of the paleoclimate simulation still rests on the researcher.  Choices will need to be made on the appropriate conditions (i.e., land-ocean configuration, topography and bathymetry, ice sheets, vegetation) for the specific paleoclimate research topic being explored.  Additional information on the component models and options that may need to be set can be found in the technical notes of these models.  We thank all those who have contributed their time and expertise for maintaining the paleoclimate versions of CESM1.

Bette Otto-Bliesner and Jeff Kiehl

 

Introduction

This document describes the procedures for creating a CESM1 paleoclimate simulation in the fully coupled (all active components) configuration.  We provide tools and examples of the process used to create paleoclimate simulations using the computing resources at the National Center for Atmospheric Research (NCAR).  This document is to be used as a guide; researchers are ultimately responsible for modifying the process to accommodate their time period of interest as well as adapting the tools to their available computer resources.

Throughout this User’s Guide we differentiate between the procedures required to create (1) near-modern (e.g., Quaternary, Pliocene) or (2) Deep-Time (pre-Quaternary) model simulations.  In near-modern simulations, the continents are in their present-day positions, and the land/sea masks do not require significant modification. Quaternary modelers are often able to use existing forcing files to simulate past climate.  By contrast, deep-time simulations require drastic modifications to the land/sea mask, and the modeler is responsible for providing the orographic/bathymetric maps for their geologic period of interest.

This document assumes a default fully coupled CESM1 configuration.  We do not describe the creation of the forcing files used in Data Model components or in stand-alone component model runs. To gain more understanding about the CESM1 component models and input files, see the CESM1 documentation (http://www2.cesm.ucar.edu/).

To contact a paleo climate liaison, please see the CESM webpage: (http://www2.cesm.ucar.edu/working-groups/pwg).