Hi, what is the sea surface elevation you start with? I guess you experience the following:
If you set up some salinity (density) distribution with large horizontal gradients it appears, that the barotropic mode rapidly adjusts to the density field in such a way, that the barotropic (sea level) pressure gradient balances the vertical integral of the baroclinic pressure gradients. (A very old adjustment problem which has been discussed first by Marsigli in the 16th or 17th century .. I have forgotten. I remember there is some remark on this in the textbook of Gill.) The point is, that the currents, which give a rough geostrophic balance to these gradients are missing in your initial field. Since the geostropic balance is the leading balance in most cases, the result may be very large currents which damage completely your initial field and may violate CFL criteria. A way out is not simple. To initialize a new model I am doing the following: - edit the tracer subroutine and set the tracer time tendency to zero. (In some cases the vertical mixing must be switched on to get a reasonable surface boundary layer. This depends on your problem.) This means, that you have tracers constant. - Run your model (with a sufficiently) small timestep. For simplicity you could switch off wind forcing. The result is a set of fields, tracers (baroclinic pressure gradient), sea level, baroclinic and barotropic velocities, where the (fixed in time) vertically integrated sea level gradient approximately balances the barotropic pressure gradient and currents are in geostrophic balance with the pressure fields. - I do not know, how long you must run the model to reach a stable state. - Alternatively, you could diagnose the geostropic baroclinic velocity field from the initial data and could initialize the model with these fields. I propose to use FERRET for this purpose. - If you have found a sufficiently stable model state, replace the simplified executable with the original one and use the last restart file to initalize the new model. - An alternative is to use the sourceterms in tracer to relax the tracer fields to the initial configuration. It is possible, that I am completely wrong with my idea. Anyway, the problem described above is typical for free surface code. You need some spinup for every model configuration. Greetings, Martin ------------------------------------------------------- This SF.Net email is sponsored by: INetU Attention Web Developers & Consultants: Become An INetU Hosting Partner. Refer Dedicated Servers. We Manage Them. You Get 10% Monthly Commission! INetU Dedicated Managed Hosting http://www.inetu.net/partner/index.php _______________________________________________ FMS-mom4 mailing list [EMAIL PROTECTED] https://lists.sourceforge.net/lists/listinfo/fms-mom4
