Re: low-pass filter

From: Adam Phillips <asphilli_at_nyahnyahspammersnyahnyah>
Date: Fri, 25 Aug 2006 10:42:27 -0600

Hi Sherry,

You can calculate a power spectra on the data both before and after the
weighting is applied. You should see a large difference between the 2
spectra, most notably the spectra calculated from the weighted data
should taper off as you move to higher frequencies away from 10 years...

http://www.ncl.ucar.edu/Document/Functions/Built-in/specx_anal.shtml
......
ts_wgt = wgt_runave(ts, wgt, 0)
nt = dimsizes(ts_wgt)
iopt = 0
jave = 5
pct = 0.1
sdof1 = specx_anal(ts,iopt,jave,pct)
sdof2 = specx_anal(ts_wgt(4:nt-5),iopt,jave,pct) ; cannot have missing

                                                   ; data
wks = gsn_open_wks("ps","test")
plot1 = gsn_csm_xy(wks,sdof1_at_frq,sdof1_at_spcx,False)
plot2 = gsn_csm_xy(wks,sdof2_at_frq,sdof2_at_spcx,False)
end

Adam

pengyb_at_cma.gov.cn wrote:
> hi, users
> thanks the people who help me.
> a low-pass filter is imposed on annual global_mean time series
> temperature change data ,which removes fluctuations with periods less
> than 10 years(11-point smooth).
> i use the function wgt = filwgts_lancos (9, 0, 0.2, -999., 1) to get
> the wgts, and use ts = wgt_runave(ts(time|:), wgt, 0) to get the smooth
> data.
> but how to know the data is 11-point smooth?
> yours sherry
>
>
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-- 
--------------------------------------------------------------
Adam Phillips			             asphilli_at_ucar.edu
National Center for Atmospheric Research   tel: (303) 497-1726
ESSL/CGD/CAS                               fax: (303) 497-1333
P.O. Box 3000				
Boulder, CO 80307-3000	  http://www.cgd.ucar.edu/cas/asphilli
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Received on Fri Aug 25 2006 - 10:42:27 MDT

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