It is the response function for the filter being used
that is important. eg: See attached
The current version of NCL has Lanczos filtering.
http://www.ncl.ucar.edu/Document/Functions/Built-in/filwgts_lanczos.shtml
See the Filter page
http://www.ncl.ucar.edu/Applications/filter.shtml
See Example 8. You can download and run the script to determine
the number of weights you need for your application. You will
lose nwgt/2 points at each end of the series.
--- The 6.3.0 release will have a Butterworth filter optimized for a narrow passband width. Note: The Butterworth and Chebyshev filters have 'end effects' also. On 4/2/14, 2:56 PM, Mahesh Varma wrote: > Hi, > I am trying to calculate Interdecadal Pacific Oscillation Index using > HadSST2 data. I am following Parker et al., 2007 method to calculate the > IPO. Parker et al. use a filter called Chebyshev filter. I am not sure if > NCL has any built in function that does Chebyshev filtering. I could > calculate IPO index without the filter and but am particularly interested > in reproducing the monthly principal component values as in Parker et al. > 2007. Does any one have a script already written to calculate IPO? Any help > will be appreciated. > Thanks, > Mahesh > > > > _______________________________________________ > ncl-talk mailing list > List instructions, subscriber options, unsubscribe: > http://mailman.ucar.edu/mailman/listinfo/ncl-talk >
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