[MITgcm-support] Shapiro filter configuration

[Jean-Michel Campin]

Hi Yuan,

The nShap[T,UV] parameter correspond to the power "n" in section 2.20
"Shapiro Filter" of the manual. The larger "n" is, the more scale
selective the filter is (the lesser effect it has on larger scale
feature).

regarding corner effects:
- which cube-sphere grid are you using ? There are some CS-32 grid-files
  that behave better than others regarding this issue.
- hard to tell much more without knowing what are the shapiro parameter
  (data.shap) you are using.

Cheers,
Jean-Michel

On Sat, Jun 25, 2011 at 09:34:16PM -0700, Yuan Lian wrote:
> OK, Just figured out nShapT=0 will turn off Shapiro filter for
> active tracers.
> nShapT=1 is an extremely bad option, which smooths out almost everything.
> 
> In atmosperhic modeling with cube-sphere grid, I noticed strong
> corner effect
> occurs if Shapiro filter is stronger, say nShapUV=2 causes much
> larger pressure
> anomaly around corners than nShapUV=4. Setting nShapUV=0 actually totally
> removes the corner effects. Is there any reason why this happens?
> Isn't Shapiro
> filter supposed to smooth the wind vectors (so the vertical winds I
> assume) than
> exaggerating them?
> 
> Thanks!
> 
> Yuan
> 
> 
> On 6/25/11 7:15 PM, Yuan Lian wrote:
> >Hi,
> >
> >Does anyone by chance know the difference between nShapT=1 and
> >nShapT=0? I noticed nShapT=1
> >has stronger smoothing effect than nShapT=0. Are they supposed to
> >behave in this way? I though
> >nShapT=1 would have weaker smoothing.
> >
> >Thanks!
> >
> >Best,
> >Yuan
> >
> >
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> 
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