how to add SSH perturbation at restart time in pop2

[zhouqian09@gmail_com]

I want to add SSH perturbation in pop2, but it seems not a variable saved in the restart file. I am wondering what its variable name is in the model’s codes, and how is SSH calculated and initialized, so I can add perturbation at the restart time for only once.Any reply and comment is highly appreciated.

 

[klindsay]

Hi,PSURF_OLD and PSURF_CUR are directly related to SSH and are in the restart file.
SSH, in units of cm, is equal to PSURF/g, where g=9.80616e2 cm/s^2.That said, there is some risk in directly changing SSH in restart files, vis PSURF.There are associated quantities in the restart files that are directly related to PSURF: PGUESS, GRADP{X,Y}_{CUR,OLD}, {U,V}TROP_{CUR,OLD}. Changing PSURF and leaving these other variables unchanged introduces an inconsistency into the model state. I do not know what the impact of such an inconsistency would be.Numerical discretizations in POP make the assumption that SSH is small compared to the thickness in the model's top layer, which for standard configurations is 10m.  This assumption should not be violated by changes to SSH.POP, as typically run in CESM, conserves volume. That is, global mean SSH is constant in time. Modifications to SSH that change the global volume of the ocean could have unforeseen consequences.Keith Lindsay

 

[zhouqian09@gmail_com]

Thank you!