Re: vinth2p with CMIP data

[1] If you are interpolating from hybrid to pressure levels,
any grid point where the surface pressure (ps) is greater than the
constant pressure level is below ground. (ps=791, the 850 is below ground).

[2] Perhaps the GFDL hybrid coefficients are different than
the ones used in vinth2p. The eqn for the 'a' and 'b' coefficients
can take slightly different forms.

On 3/27/12 12:10 PM, kelly lombardo wrote:
> I was just interpolating to 850; 700; 500; 300; 200 hPa, nothing below
> ground level. Could it be that this routine isn't calibrated for GFDL
> model output, and can only be used with the CESM? I assumed that the A
> and B coefficients would be alright since it looks like these
> coefficients in both the GFDL and CESM are used for the middle point in
> between the model grid levels. Maybe this was an incorrect assumption?
>
>
>
> ------------------------------------------------------------------------
> *From:* Dennis Shea <shea@ucar.edu>
> *To:* kelly lombardo <kellyann7319@yahoo.com>
> *Cc:* "ncl-talk@ucar.edu" <ncl-talk@ucar.edu>
> *Sent:* Tuesday, March 27, 2012 1:50 PM
> *Subject:* Re: [ncl-talk] vinth2p with CMIP data
>
> If you are interpolating, there should be no winds that
> look "too strong". If you are extrapolating (below ground level)
> then this could be the case. vinth2p_ecmwf will extrapolate
> temperature (using the lapse rate) and/or geopotential (lapse
> rate and hydrostatic formula). *All* other variables are
> set to the the nearest non-missing value. This could result
> in "too strong" winds.
>
> As noted in the documentation, the vinth2p was taken directly
> from the old model processor. NCL changed nothing.
>
> My suggestions:
> (1) do not extrapolate [*all* extrapolations not guided
> by physics are dangerous, even then use with caution]
>
> (2) Look at "Grid Fill" examples at
> http://www.ncl.ucar.edu/Applications/grid_fill.shtml
> In particular the ones using 'poisson_grid_fill'
> Good Luck
>
> On 03/27/2012 11:27 AM, kelly lombardo wrote:
> > Hey everyone
> >
> > I am trying to interpolate CMIP GFDL-ESM2M data (such as U, V, T) which
> > is stored on hybrid sigma-pressure coordinates to pressure coordinates
> > using vinth2p. I was able to interpolate the data, but the winds look
> > too strong. Has anyone encountered a similar problem? Or does anyone
> > know where I can find the vinth2p code so I can see how the
> > interpolation is calculated?
> >
> > Thanks
> > kelly
> >
> >
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>
>
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Received on Tue Mar 27 13:20:00 2012