Re: IPO index calculation

From: Dennis Shea <shea_at_nyahnyahspammersnyahnyah>
Date: Thu Apr 03 2014 - 09:43:49 MDT

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
>
>
>
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Received on Thu Apr 3 09:43:59 2014

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