[ncl-talk] Wheeler Kiladi Spectrum

[Dennis Shea]

The underlying fortran code uses FFTs at each latitude. It assumes the data
are global (cyclic in longitude). I am not sure you can modify the code to
do what you want.

If you work on non-global data, what does 'wave number' mean?

Here is a f77 code snippet:

========================================================
c--------------------------------------------------------------------
c---------------COMPUTING SPACE-TIME SPECTRUM for EE1----------------

            DO T = 1, NT
               DO N = 1, NL
c CEEa(n) contains the grid values around a latitude circle
                  CEEA(N) = EE1(N,T)
               END DO
               CALL CFFTF (NL, CEEA, WSAVE1)
               DO N = 1, NL
c Normalize
                  EE1(N,T) = CEEA(N)/DBLE(NL)
               END DO
            END DO

c Now the array EE(n,t) contains the Fourier coefficients (in planetary
c wavenumber space) for each time.

            DO N = 1, NL
               DO T = 1, NT
c CEEb(t) contains a time-series of the coefficients for a single
c planetary zonal wavenumber
                  CEEB(T) = EE1(N,T)
               END DO
               CALL CFFTF (NT, CEEB, WSAVE2)
               DO T = 1, NT
C Normalize
                  EE1(N,T) = CEEB(T)/DBLE(NT)
               END DO
            END DO

c Now the array EE1(n,t) contains the space-time spectrum.
====================================================

I do not think you can isolate a region for space-time spectra.



On Thu, Aug 17, 2017 at 7:53 AM, Adithyan Velloor <adtynvellooor at gmail.com>
wrote:

> Dear NCL users,
>
> I am trying to plot the wheeler killadi spectrum (wave number spectrum)
> for a specific region (Indian Ocean basin from 40-140 degree East). The in
> built script for the spectrum is for the entire longitude 0 to 360.
>
> Someone please tell me a way to take a specific longitude region to get
> the spectrum correctly.. Below is the script to get the wheeler kiladis
> spectra if I consider the entire longitudional belt. Kindly suggest the
> necessary changes to be made in the script to modify it for my purpose.
>
>
> load "$NCARG_ROOT/lib/ncarg/nclscripts/csm/gsn_code.ncl"
> load "$NCARG_ROOT/lib/ncarg/nclscripts/csm/gsn_csm.ncl"
> load "$NCARG_ROOT/lib/ncarg/nclscripts/csm/contributed.ncl"
> load "$NCARG_ROOT/lib/ncarg/nclscripts/csm/diagnostics_cam.ncl"
>
>   case     = "wheeler"
>   diro    = "./"
>   latN    = 15
>   latS    = -latN
>
>   nDayWin = 96
>   nDaySkip = 1
>
>    opt  = True
>    opt at debug= True
>    opt at pltType     = "eps"
>    opt at cnLinesOn   = False   ; turn off contour lines
>
>    spd = 1
>    var = "olr_fav"
>
>  setfileoption("nc", "FileStructure", "Advanced")
>
>    f        =  addfile("olr.nc", "r")
>  olr_fav =  f->olr(0:14457,{latS:latN},0:141)
>
> ;function ismissing (olr_fix)
>         return_val [dimsizes(olr_fix)] :  logical
>
>  ;set_default_fillvalue("float",   1.e20)
>
>
>  wkSpaceTime (olr_fav, diro, case, var             \
>               ,latN, spd, nDayWin, nDaySkip, opt  )
>
>
> Thanks
>
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