Ocean

Ocean#

The ocean component of CESM3 is the Modular Ocean Model version 6 (MOM6).

It can be helpful for people interested in ocean science to run simulations with only active sea ice, wave, and ocean components and atmospheric forcing. This exercise will teach you how to run one of these ice-wave-ocean simulations.

This exercise was originally created for POP by Nancy Norton, David Bailey, and Mike Levy and adapted for MOM6 by Gustavo Marques and William Xu.

Learning Goals#

  • Student will learn what G compsets are, the difference between G and GW compsets, the types of forcing available to run one, and how to run one.

  • Student will learn how to make a namelist modification that turns off the submesoscale parameterization and compare results with a control experiment.

  • Student will learn how to make a source code modification that changes zonal wind stress and compare results with a control experiment.

  • Student will learn what a GW1850MARBL_JRA compset is and compare it to the GW_JRA compset.

Exercise Details#

  • All exercises use the same code base as the rest of the tutorial.

  • You will be using the GW_JRA compset at the TL319_t233_wg37 resolution.

  • You will run a control simulation and three experimental simulations. Each simulation will be run for one year.

  • You will then use ‘ncview’ (http://meteora.ucsd.edu/~pierce/ncview_home_page.html) to evaluate how the experiments differ from the control simulation.

Useful MOM6 references#

MOM6 Examples Wiki

MOM6’s documentation

CESM MOM6 Discussion Forum

What is a G/GW case?#

The G compsets have active and coupled ocean and sea-ice components. The G compsets require boundary forcing from the atmosphere. The G compsets are forced with atmospheric data that does not change interactively as the ocean and sea-ice evolve in time. The land and land ice are not active during a G compset experiment and the runoff is specified. A GW compset experiment also has an active wave model.

In this exercise, you will be running the GW compsets. In the sea ice challenge exercise, you will be running the G compsets.

G/GW Compset forcing data#

There are two types of temporal forcing for G compsets:

  • Repeat Year Forcing (RYF) is 12 months of atmospheric data (from a particular time period) that repeats.

  • Interannual varying forcing (GIAF) is forcing that varies by year over the time period (1958-2023).

We use the following interannual forcing for G compsets:

Post processing and viewing your output#

  1. You can create an annual average of the first year’s data for each simulationg using the ncra (netCDF averager) command from the netCDF operators package (NCO).

ncra $OUTPUT_DIR/*.mom.h.0001*nc $CASENAME.mom.h.0001.nc

  1. Create a file that contains differences between each of the experiments and the control simulation

ncdiff $CASENAME.mom.h.0001.nc $CONTROLCASE.mom.h.0001.nc $CASENAME_diff.nc

  1. Examine variables within each annual mean and the difference files using ncview

ncview $CASENAME_diff.nc

  1. You can also look at other monthly-mean outputs or component log files.

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