Re: About Rotated EOF patterns of NCEP reanalysis 500mb monthly data

From: Adam Phillips <asphilli_at_nyahnyahspammersnyahnyah>
Date: Tue Nov 06 2012 - 14:29:08 MST

Hi Waqar,
Looking at your script, I don't see anything wrong. That leaves me
trying to answer why the patterns are not what you expected them to be,
and of course I cannot answer that. The patterns depend on the data you
use. You can try running your script on other data, say, the NCEP/NCAR
Reanalysis, to see if the results are what you expect.
Good luck,
Adam

On 11/6/12 12:31 PM, Waqar Younas wrote:
> Hi
> It does not make any difference because even without reordering, i was
> getting the EOF patterns in order as first mode explained variance was
> 13.3% and second one is 10% and so on. The patterns did not change.
> I do not know where i am making mistake because especially for PNA,
> the most variance should be in Western side but my PNA pattern is
> capturing variability on Eastern side too. Now i am attaching the
> whole code which i modified using eof_4.ncl.
> Thanks.
>
>
>
>
>
> On Tue, Nov 6, 2012 at 9:05 AM, Dennis Shea <shea@ucar.edu
> <mailto:shea@ucar.edu>> wrote:
>
> The documentation for eofunc_varimax includes the following
>
> " The order of the returned varimax rotated EOFs is not
> necessarily in strict descending order as returned by eofunc or
> eofunc_varimax_Wrap. The user should use the
> *eofunc_varimax_reorder* procedure to place the returned varimax
> rotated EOFs into strict descending order."
>
> http://www.ncl.ucar.edu/Document/Functions/Contributed/eofunc_varimax_reorder.shtml
>
> It seems to me you should have"
>
> ev_rot = eofunc_varimax_Wrap(eof,1)
> printVarSummary(ev_rot)
>
> eofunc_varimax_reorder(ev_rot)
> printVarSummary(ev_rot)
>
> ; ev_rot will be orthogonal. However, 'ev_rot1'
> ; will not tield principal components that are independent
>
>
>
> ev_rot1 = eofunc_ts_Wrap (wx, ev_rot, optETS)
>
>
> On 11/05/2012 06:23 PM, Waqar Younas wrote:
>
> Hi all,
> I need help in performing the rotated EOF of NCEP/NCAR
> reanalysis data
> using NCL. I used the code eof_4.ncl present on ncl functions
> page. This
> code use the same data i.e. 500mb monthly data set from
> NCEP/NCAR from
> 20S to 90S but this code only calculates the EOF. This code is
> originally written for calculating AAO oscillations.
> For my case, i change the region from 20-90 N and for rotated
> EOF, i
> added these lines in the code
>
> ;;;;;;; Rotation of EOF
>
> ev_rot = eofunc_varimax_Wrap(eof,1)
> printVarSummary(ev_rot)
> ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
> ev_rot1 = eofunc_ts_Wrap (wx, ev_rot, optETS)
> ev_rot1 = dim_standardize_n( ev_rot1, 0, 1)
> ;
> =================================================================
> ; Regress
> ;
> =================================================================
> ev_regres = ev_rot ; create an
> array w
> meta data
> do ne=0,neof-1
> ev_regres(ne,:,:) = (/ regCoef(ev_rot1(ne,:),
> xAnom(lat|:,lon|:,time|:)) /)
> end do
> At the end, i plot this ev_regres which contains REOF1 and REOF2.
> According to many papers and definitions of Climate prediction
> centre,
> the first REOF should be NAO and second should be PNA. In my
> case, the
> first EOF is NAO but it is slightly different. The second EOF is
> capturing PNA but it is not exact. I am attaching the figure.
> For my research i need PNA pattern which is second REOF. It is
> capturing
> PNA but also some other variabilties too.
> Thanks for the help in advance.
>
>
>
>
>
> --
> Best Regards
>
> Waqar Younas
> PhD Candidate
> Natural Resources and Environmental Studies (NRES)
> University of Northern British Columbia (UNBC)
> Canada
>
>
>
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>
>
>
>
> --
> Best Regards
>
> Waqar Younas
> PhD Candidate
> Natural Resources and Environmental Studies (NRES)
> University of Northern British Columbia (UNBC)
> Canada
>
>
>
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Received on Tue Nov 6 14:29:20 2012

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