[ncl-talk] Computing geopotential height

[markus.mingel at libero.it]

Hi Carlos,


thanks for sharing your scripts. I revised my code and finally I found the bug. In vinth2p_ecmwf I used as tbot the surface geopotential instead of bottom temperature. After providing the right surface temperature and surface geopotential as orog*9.81 I get reasonable geopotential heights.

Best regards,


Markus

> Il 14/11/2022 14:17 Carlos Marques <cafm at ua.pt> ha scritto:
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> Hi,
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> Attached there are two scripts that I used to compute Geopotential for CMIP6 model MPI-ESM1.2-LR and to interpolate after to pressure levels.
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> Also attached there are 3 figures that compare the geopotential computed and interpolated to pressure levels with NCL with that provided by MPI. You may see that they compare fairly well.
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> You should check that every variable is what NCL's expects (units, coordinates ordering, etc. ). I think that for example you P0 is in hPa, but NCL expects that to be in Pa.
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> I don't think that you can compute and interpolate to pressure levels without the surface geopotential.
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> Hope that helps.
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> C. A. F. Marques
> CESAM & Physics Department
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> University of Aveiro
> 3810-193 Aveiro. Portugal
> http://www.cesam.ua.pt/cafmarques
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> ---------------------------------------------
> 
> From: ncl-talk <ncl-talk-bounces at mailman.ucar.edu> on behalf of markus mingel via ncl-talk <ncl-talk at mailman.ucar.edu>
> Sent: Monday, November 14, 2022 12:42:27 PM
> To: ncl-talk at ucar.edu
> Subject: [ncl-talk] Computing geopotential height
> 
> 
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> Hi All,
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> I am trying to derive the geopotential height of a given CMIP6 model from its air temperature and humidity.
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> Firstly, I compute the geopotential in the native hybrid coordinates using the NCL function cz2ccm, then I interpolate the just computed geopotential to some pressure levels using vinth2p_ecmwf.
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> The comparison of the geopotential computed with my script (attached) with the zg downloaded from ESGF shows large differences, so I was wondering if anyone could suggest me what's wrong in my script? 
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> Besides, when the variable phis (surface geopotential (m^2/sec^2)) is not available as input, which values I should use? Is it possible to compute it in anyway with NCL?
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> Thanks into advance for help,
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> Best,
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> Markus
> 
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