low-pass filter problem

Hi all,

I would like to use a low-pass filter on one monthly data to remove
the signal with period less than 1 year.
When I check the result, I find there still a signal in high frequency
band.

My script as follow:
  print("generates the weights for low pass filter")
     ihp = 0
     nsigma = 1.
     befaft = 17 - 1 ; number of points to use before and after
current point
     nwt = 2*befaft + 1 ; total number of weights
     fca = 0.06
     fcb = -999.
     wts_t = filwgts_lancos (nwt, ihp, fca, fcb, nsigma)
; opt=0 is chosen for wgt_runave when applying the weights to, say, a
time series
   opt = 0

; low pass data
   x_pass = wgt_runave_Wrap(x,wts_t,opt)
   x_new = x_pass(lat|:,lon|:,time|24:tmax-24)

   x_org_ts = x({lat|0},{lon|180},time|:)
   printVarSummary(x_org_ts)
   x_new_ts = x_new({lat|0},{lon|180},time|:)
   printVarSummary(x_new_ts)

;------------------------------------------------------------------
; set parameter for spectrum
;------------------------------------------------------------------
   print("calculating spectrum of eof time series....")
   d = 1 ;Remove the series mean and least squares linear trend.
   sm = 7
   pct = 0.10

   spec_org = specx_anal(x_org_ts,d,sm,pct)
   splt_org = specx_ci(spec_org, 0.1, 0.95)

   spec_new = specx_anal(x_new_ts,d,sm,pct)
   splt_new = specx_ci(spec_new, 0.1, 0.95)

Any suggestions??

Also I have another question: how to set the precision of the Y axis?
I used these two sources:
   res_spec_at_tmYLAutoPrecision = False
   res_spec_at_tmYLPrecision = 4
Anything else??

Thanks in advance.

Guangshan

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Received on Fri Jun 05 2009 - 10:11:52 MDT