[ncl-talk] Computing geopotential height

[Carlos Marques]

Hi,


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.

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.


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.


I don't think that you can compute and interpolate to pressure levels without the surface geopotential.


Hope that helps.


C. A. F. Marques
CESAM & Physics Department
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


Hi All,

I am trying to derive the geopotential height of a given CMIP6 model from its air temperature and humidity.

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.

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?

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?

Thanks into advance for help,

Best,

Markus
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