Re: [ncl-talk] Vertical Interpolation

> Happy New Year!

Happy New Year to u also!

> I am trying to interpolate the CCSM and NCEP/NCAR Reanalysis into Sigma
>coordinates.
> I was wondering if there are subroutines can convert the data from Hybird
>to Sigma coordinates and convert from Pressure to Sigma coordinates.

[a] hybrid to sigma

    The next release of NCL [a033; hopefully very soon] has a function
    called "hyi2hyo". The purpose is to interpolate from data on
    one set of hybrid levels to another set of hybrid levels.
    
    http://www.ncl.ucar.edu/Document/Functions/Built-in/hyi2hyo.shtml
    
    Hybrid levels are a combination of pressure levels and sigma levels
    
                     p(k) = A(k)*PO + B(k)*PS
                            ^^^^ ^^^^
                            pressure sigma
                            
    Thus, it seems that this function could be used by setting
    the A(k) to 0.0.
    
    f = addfile ..., "r")
    hyai = f->hyam ; input A(k)
    hybi = f->hybm ; input B(k)
    xi = f->X ; variable to be interpolated
    p0 = f->P0 ; reference pressure (Pa)
    
    fP = addfile ("file containing surface pressure", "r")
    psfc = fP->PSFC ; surface pressure (Pa)
    
    hybo = sigma ; *your* B(k) [ sigma levels ]
    nsig = dimsizes(hybo)
    hyao = new ( nsig, typeof(hybo))
    hyao = 0.0 ; set output A(k) to 0.0

    xo = hyi2hyo(p0,hyai,hybi,psfc,xi,hyao,hybo,0)
or, better,
    xo = hyi2hyo_Wrap(p0,hyai,hybi,psfc,xi,hyao,hybo,0) ; contributed.ncl
    printVarSummary(xo)
    

[b] pressure to sigma

    It seems to me that a combination of
    
    http://www.ncl.ucar.edu/Document/Functions/Built-in/pres_sigma.shtml
    and
    http://www.ncl.ucar.edu/Document/Functions/Built-in/int2p.shtml
    
    Depending upon the shape of psfc
                          
    pSigma = pres_sigma (sigma, psfc) ; pSigma(klvl,nlat,mlon)
    pSigma = pres_sigma (sigma, psfc) ; pSigma(ntim,klvl,nlat,mlon)
                                                 time,pSig, lat, lon)

    f = addfile ("reanalysis.." , 'r")
    xi = f->X ; (time,plevel,lat,lon)
    pi = f->pressure_levels ; [*]
    
    linlog = 0 or 1
    x_out = int2p(pi,xi(time|:,lat|:,lon|:,plevel|:), \
                   pSigma(time|:,lat|:,lon|:,pSig|:), linlog)

good luck
D
    

_______________________________________________
ncl-talk mailing list
ncl-talk_at_ucar.edu
http://mailman.ucar.edu/mailman/listinfo/ncl-talk
Received on Wed Jan 04 2006 - 11:27:54 MST