Re: questions about interpolation by NCL

From: Dennis Shea <shea_at_nyahnyahspammersnyahnyah>
Date: Wed, 6 Dec 2006 08:06:27 -0700 (MST)

> I'm trying to interpolate topography by f2fsh_Wrap
> into a lower resolution one, however, the interpolated
> topography in ocean has some positive and negative
> values which cross the whole ocean where the original
> values are all zeros. So when I turn back to the
> arithmetic, I find that the f2fsh_Wrap, f2gsh_Wrap and
> so on are all using the spherical harmonics.
> Therefore, I think the whether some pseudo waves or
> results are generated by using the NCL interpolation
> functions.Or in another words, the rank data cannot be
> interpolated simply by the NCL functions, right?
> ___________________________________________________________

f2fsh_Wrap/g2gsh_Wrap use spherical harmonics to perform
the regridding. These are best applied to fields that
are not bounded (eg: zero for some fields like precipitation)

When spherical harmonics are applied to bounded fields
the results exhibit "spectral ringing" ... small oscillations
about aero in your case.

Use linint2_Wrap.

Good luck

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Received on Wed Dec 06 2006 - 08:06:27 MST

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