Experiment with the Atmosphere
How do I setup and run an experiment with prescribed ocean forcing?
How is the ocean forcing defined?Objectives
In this lesson, we will learn about setting up experiments using the atmosphere with the ocean in data mode with prescribed SST forcing.
We will start with a basic case of running an atmosphere-forced experiment. We will then consider a specific scientific question and setup experiments using the atmosphere-forced experiment to answer this question, following the Drought Working Group Experiments.
Running the Atmosphere
Anytime we want to setup a new expeiment, we will create a newcase using the
create_newcase script. The script requires us to provide several things when we run it. Let’s figure out the correct options for setting up a case with the atmosphere in forced mode.
We can name our case whatever we want
We are using this resolution, but we will need to check if it is available for what we want to do
We will need to determine the right compset for this experiment.
This is our project code. It does not change.
compset do we use?
There are two ways to determine which compset to use.
- There is a tool:
$ CIMEROOT/scripts/query_config --compsets
We can see from this that the compsets with
cam, the atmosphere model, active all start with
F, but it gives us the complicated long name and doesn’t provide us with all the information we need. Let’s take a look at the website for more information.
Notice that the website indicates which version of CESM you are using in the upper right corner. Our version is
CESM 2.1.1. Let’s scroll until we find the
There are several options here, but the most basic option is
FHIST. This is an atmosphere forced run with prescribed ocean and ice using historical GHG forcing.
Remember that the compset determines which grids are
scientifically validated, meaning which ones have been tested.
Is our resolution grid
scientifically validatedfor any of the
Take a look at the webpage and view the scientifically validated grid for the F-composets. See if our grid is listed.
Create your case
Create a new case using the
FHISTcompset with our grid and project code Call the case whatever you wish.
$ ./create_newcase --case ~/cases/testatmF --res f19_g17 --compset FHIST --project UGMU0032
You will get an error. Read the error.
What does it mean? What do you need to do to setup your case with this compset and grid resolution?
create_newcaseis letting us know that our grid is not scientifically validated for this compset. It tells us we can use the
--run_unsupportedoption to use this grid and compset anyway.
$ ./create_newcase --case ~/cases/testatmF --res f19_g17 --compset FHIST --project UGMU0032 --run-unsupported
Complete the setup, build the case and run it for 1-month as a test
$ ./case.setup $ qcmd -- case.build $ ./xmlchange STOP_OPTION=nmonths $ ./xmlchange STOP_N=1
How is the ocean prescribed in this run?
Full documentation on
DOCN is here
The file specifying the SST and Ice data is located in
SSTCE_DATA_FILENAME. We can use
xmlquery to see what this is set to.
$ ./xmlquery SSTICE_DATA_FILENAME
- Let’s look at the description of this variable in
- Prescribed SST and ice coverage data file name. Sets SST and ice coverage data file name. This is only used when DOCN_MODE=prescribed.
Based on the filename, this appears to be SST and Ice data on a 1x1 degree grid from 1850-2017. We can do
ncdump -h on the file to get more information.
$ ncdump -h /glade/p/cesmdata/cseg/inputdata/atm/cam/sst/sst_HadOIBl_bc_1x1_1850_2017_c180507.nc
The data contains several variables:
The global attributes tell us how this data was made and even give us a reference for it. We can look this up in more detail if we want. For now, let’s take a look at the data using
$ module load ncview $ ncview /glade/p/cesmdata/cseg/inputdata/atm/cam/sst/sst_HadOIBl_bc_1x1_1850_2017_c180507.nc
We now know how to create a case with ocean prescribed.
We know how to set the file that prescribes the ocean.
We have an example file that prescribes the ocean.