[ncl-talk] power spectrum analysis

[Edwin Marco]

Hi,
I am new to ncl and I have been trying to plot the spectrum of daily
rainfall data using this kind of script ( attached below) unfortunately I
am not getting there, please can you help me on how I can modify the
attached script which was intended for frequency (cycles/month) as to get
frequency (cycles/day).
Thanks in advance.

Edwin

spec_1.ncl
;
; Concepts illustrated:
;   - Calculating and plotting spectra
;************************************************
;
; These files are loaded by default in NCL V6.2.0 and newer
; load "$NCARG_ROOT/lib/ncarg/nclscripts/csm/gsn_code.ncl"
; load "$NCARG_ROOT/lib/ncarg/nclscripts/csm/gsn_csm.ncl"
;************************************************
begin
;************************************************
; variable and file handling
;************************************************
   fn  = "SOI_Darwin.nc" ; define filename
   in  = addfile(fn,"r")                                 ; open netcdf file
   soi  = in->DSOI                                       ; get data
;************************************************
; set function arguments
;************************************************
; detrending opt: 0=>remove mean 1=>remove mean and detrend
  d = 0
; smoothing periodogram: (0 <= sm <= ??.) should be at least 3 and odd
  sm = 7
; percent tapered: (0.0 <= pct <= 1.0) 0.10 common.
  pct = 0.10
;************************************************
; calculate spectrum
;************************************************
  spec = specx_anal(soi,d,sm,pct)
;************************************************
; plotting
;************************************************
   wks  = gsn_open_wks("png","spec")               ; send graphics to PNG file

   res = True					   ; plot mods desired
   res at tiMainString = "SOI"		           ; title
   res at tiXAxisString = "Frequency (cycles/month)"  ; xaxis
   res at tiYAxisString = "Variance"                  ; yaxis

   plot=gsn_csm_xy(wks,spec at frq,spec at spcx,res)     ; create plot
;***********************************************
end
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