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

Hi Phillips
The data i used is NCEP/NCAP reanalysis of 500mb monthly geopotential
height from 1950-2000.
I got my results correct. The only confusion remaining is when i calculate
only 2 rotational components the results are not exact, but when i
calculate the 10 rotational components and plot only 2, the results are
more like NAO (first component) and PNA (second component). Please find
attached figure when i calculate 10 components and plot first 2 components.
The other figure (when i calculate only 2 components and plot them) is
attached in the first message above. I do not know why there is such
difference?

Thanks.

On Tue, Nov 6, 2012 at 1:29 PM, Adam Phillips <asphilli@ucar.edu> wrote:

> 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> 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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>>> ncl-talk mailing list
>>> List instructions, subscriber options, unsubscribe:
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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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>
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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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