Overview
This page provides access to a global barotropic model using the spectral transform technique.
The model integrates the fully non-linear divergent barotropic vorticity equation, using prescribed divergence and/or orography to force the rotational flow. For more information on the model equations and typical experimental results, see:
Sardeshmukh, P.D. and Hoskins, B.J. (1988) On the generation of global rotational flow by steady idealised tropical divergence. J.Atmos.Sci., 45, 1228-1251. (Abstract and PDF)
The model exists as a program library in nupdate format, which allows a fixed version of the code to be temporarily updated for each experiment.
The nupdate code maintanance tool and model Support Libraries are available from the main Dynamical Models page.
Using the Model
The job-scripts linked below are coded to run on Unix/Linux workstations in the Department of Meteorology, but can be modified to run on other linux machines.
To run the model, copy the job-script to your Unix filespace; set the MACHINE variable and other switches appropriately, then run the script. The support libraries will be loaded automatically.
Note: the script contains some defunct batch commands, but experiments should in general run interactively within a few seconds, unless you are running at a resolution to rival ECMWF!
To run the model elsewhere, copy the job-script, program library, any required model updates and the all support libraries. Compile and load the main support libraries using the same compiler and options that you will use for the model itself. Modify the paths, compile command and any other syntax.
The barotropic model creates a data file containing a user-defined selection of global lat-long fields at a user-defined frequency. The format of this file is UTF, an antiquated local ACII-coded format. New users are recommended to replace this, writing (un)formatted data to be read into a scripted graphics package.
Please note that we are not able to support remote users of the dynamical models.
Idealised test-job
This section describes a test-job for the barotropic model and provides links to the job-script, model, support libraries etc.
The test run is similar to the first experiment in Sardeshmukh and Hoskins (1998: J.Atmos.Sci.,45,1228-1251), hereafter SH88. It uses the non-linear divergent barotropic vorticity equation, with the vorticity freely evolving, forced by a prescribed idealised divergence. The experiment corresponds most closly to that in SH88 Fig.1d, the model set-up differing in the following ways:
-
T21 and del^8 hyperdiffusion with a 4 hour timescale at n=21
-
The divergence forcing is modified to remove its zonal average, giving compensating convergence around the equator
-
The zonal flow evolves freely, being modified by the non-linear eddy vorticity fluxes
-
The integration is for 10 days only
Plots of initial state and forcing.
Plots of eddy streamfunction and vorticity at days 5,10.
The model exists as a program library in nupdate format, which allows a fixed version of the code to be temporarily updated for each experiment.
The nupdate code maintanance tool and model Support Libraries are available from the main Dynamical Models page.
Model program library (binary)
Source listing with nupdate line numbering
job-script for idealised divergence forcing on a super-rotation initial state
output listing from job-script
List of model updates used by the test job - each contains comments describing the code modifications:
|
