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Initialized Prediction

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Initializing the Model

Overview

Teaching: min
Exercises: min
Questions

  • How to setup model initial conditions?

Objectives

Setting up Experiments - Review

To setup experiments with CESM, we setup and configure the following things:

Understanding Initial Conditions in CESM

Initial conditions tell the model what state to start from. The files that contain this information are called restart and intial condition files. They represent an instantanous state of each model component at a given time. There are multiple restarts for each componenet of the model.

Initial Conditions in our B1850 simulation (Assignment #3)

Let’s take a look at the initial conditions we used for some of our previous experiments:

$ cd /glade/u/home/cstan/cases/b.day1.0
$ ./xmlquery RUN_TYPE,RUN_STARTDATE,RUN_REFDATE,RUN_REFCASE,GET_REFCASE,RUN_REFDIR

Results in group run_begin_stop_restart
	RUN_TYPE: hybrid
	RUN_STARTDATE: 0001-01-01
	RUN_REFDATE: 0301-01-01
	RUN_REFCASE: b.e20.B1850.f19_g17.release_cesm2_1_0.020
	GET_REFCASE: TRUE
	RUN_REFDIR: cesm2_init

RUN_TYPE=hybrid, so this indicates the information in the other variables need to be set and that this run uses initial conditions from another CESM run to start it.

GET_REFCASE=TRUE means that the code will get the initial condition/restart files for you from the RUN_REFDIR. If it is FASLE, we have to “stage” (meaning copy) the initial condition/restart files in the case run directory ourselves. As an example, we did this in Assignment #4.

RUN_REFDIR is set to the default value of cesm2_init. This is a preset directory of initial condition files for starting CESM2 simulations. The full path is: /glade/p/cesmdata/inputdata/cesm2_init/

RUN_REFCASE tells it which files in RUN_REFDIR to use. Let’s take a look:

$ ls /glade/p/cesmdata/inputdata/cesm2_init/b.e20.B1850.f19_g17.release_cesm2_1_0.020*

0301-01-01

The RUN_REFDATE tells us which of these we are using (0301-01-01)

$ ls /glade/p/cesmdata/inputdata/cesm2_init/b.e20.B1850.f19_g17.release_cesm2_1_0.020/0301-01-01/

b.e20.B1850.f19_g17.release_cesm2_1_0.020.cam.i.0301-01-01-00000.nc     b.e20.B1850.f19_g17.release_cesm2_1_0.020.ww3.r.0301-01-01-00000
b.e20.B1850.f19_g17.release_cesm2_1_0.020.cam.r.0301-01-01-00000.nc     rpointer.atm
b.e20.B1850.f19_g17.release_cesm2_1_0.020.cam.rs.0301-01-01-00000.nc    rpointer.drv
b.e20.B1850.f19_g17.release_cesm2_1_0.020.cice.r.0301-01-01-00000.nc    rpointer.glc
b.e20.B1850.f19_g17.release_cesm2_1_0.020.cism.r.0301-01-01-00000.nc    rpointer.ice
b.e20.B1850.f19_g17.release_cesm2_1_0.020.clm2.r.0301-01-01-00000.nc    rpointer.lnd
b.e20.B1850.f19_g17.release_cesm2_1_0.020.cpl.r.0301-01-01-00000.nc     rpointer.ocn.ovf
b.e20.B1850.f19_g17.release_cesm2_1_0.020.mosart.r.0301-01-01-00000.nc  rpointer.ocn.restart
b.e20.B1850.f19_g17.release_cesm2_1_0.020.pop.r.0301-01-01-00000.nc     rpointer.ocn.tavg.5
b.e20.B1850.f19_g17.release_cesm2_1_0.020.pop.ro.0301-01-01-00000       rpointer.rof

These are all the files that the model needs to start this run. Notice that they begin with RUN_REFCASE

So what does RUN_STARTDATE do?

Even though the restarts we start from begin on 0003-01-01, we can tell the model to begin our experiment with whatever we want the startdate to be. This is because our simulation does not need to match any specific, real date. You can see in my experiment that the RUN_STARTDATE is set to 0001-01-01 and the output begins at that date:

$ cd /glade/derecho/scratch/cstan/archive/b.day1.0/ocn/hist
$ ls -lt

Important Note: You can specify a new startdate for your run if the RUN_TYPE=hybrid. You cannot do this if your RUN_TYPE=branch.

Now that we know better how initializing the model works, we will learn about initialized prediction experiments.

Key Points

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