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Negative PHIS after spectral filtering by EUL dycore

Hello all,

I have a question regarding the spectral filtering performed by the EUL dycore on PHIS. I've read over the response on a somewhat similar question here: http://forum.cgd.ucar.edu/archive/index.php/t-929.html, but I have an additional question. I'm running CESM1.0.4 with CAM4 physics, CLM and DOCN using a highly idealized landmask and land fraction that was created following the paleo group's procedures. The land itself is simple geometric shapes of elevation 25m and is smoothed along the coastlines. This experiment is part of a series of runs, some of which have all-ocean surface boundary. As such, I have used the APE gravity of 9.79764 to calculate the input PHIS in bnd_topo.

I noticed that when the spectral filtering of PHIS occurs during the model initialzation, that it is setting the near-coast ocean grid points to as low as -10 m2/s2 and is setting some slightly inland land points to about +10 m2/s2 greater than the input data. I'm not concerned about the inland positive increase, but I am curious as to whether the negative PHIS in the ocean near the coastlines normally occurs or if this is a problem that needs corrected.

Thank you for any help.

mveres
 
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