Setting the RUN TYPE

Overview

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Questions

• What are CESM RUN Types and how do I set them?

Objectives

CESM has three types of runs that define how the model starts or is initialized. They are set by the RUN_TYPE variable in the env_run.xml files.

1. STARTUP: All model components are initialized from basic default initial conditions.
2. HYRBRID: Model components are started from a user-specific CESM simulation., but I want to make some modifications to the run itself.
3. `BRANCH’: Model components are started from exact restart files and mimic exactly what the model would have done if it had been allowed to continue from where it was started.

When to use HYBRID vs. BRANCH

Use HYBRID when you do not need bit-for-bit reproducibility. For example, I want to start a simulation from a date in a previous one where I make a change to some part of the model. Then I want to compare my new run with the previous one. This would be a HYBRID simulation.

Use BRANCH when you want the model to reproduce exactly what it would have done if it have never been stopped, but you need to change it to have higher frequency output part way through the run.

If you use HYBRID or BRANCH you also specify RUN_REFCASE to tell it what case you are starting from and RUN_REFDATE to specify the date stamp of the reference case you are starting with

What is the RUN_TYPE for our new experiment?

Use xmlquery to find out the RUN_TYPE for our new experiment

Key Points