Regionally coupled

Unified Model

Setting up a GCM with full ocean-atmosphere coupling in some areas, but with prescribed SSTs in others is a little complicated but once you've gone through the process once its not too onerous. The UM User Interface can only cope with the choice between atmosphere-only and coupled versions, so you have to run the coupled model, supplying a modification to the code. The technique actually uses Haney forcing, whereby the SSTs in the area you wish to prescribe them are actually calculated by the coupled model but then relaxed back to your prescribed values on a very short timescale (pretty much instantaneously). This is a standard choice within the User Interface, and the modification to the model code just applies Haney forcing in the required region rather than globally.

You will need to have copies of 2 pieces of extra code. One is a Fortran script which generates a set of Haney forcing coefficients for your region of interest. This is called make_haney_coeffs.f. You run this script prior to running the UM. The other is a Unified Model modification set ("modset") which makes the model read in these haney coefficients instead of the value set in the User Interface. This is called haney.mod. Finally you will need a Unified Model ocean grid land-sea mask, in netcdf format, called umgrid_hires.nc. Copies of all 3 of these files can be obtained by clicking on the filing cabinet icon below. They are in a tar file called regional_coupling_files.tar. Download and unpack this file.

The buttons on the left will take you through the steps you need to follow to create and use a regionally coupled version of the Unified Model.



link to files

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Information on the regionally coupled version of the Unified Model is maintained by Pete Inness.

email: pete@met.reading.ac.uk phone: 0118 3785583