Re: vector eof/pca (e.g. u- and v-component of current data)

Hi,

Thank you very much for the quick reply and the help so far!
I will try to get a hold on the Wilks reference, it seems our library
doesn't stock it.
I assume the resulting EOF and also the interpretation will be quite
different between the two mentioned methods:

1) eofunc of data(time,lat,lon,component)
2) eofunc of data(time,2xlat,lon)
    with 2xlat meaning using merged u- and v- field along the meridional axis
!?

2011/3/14 gibies george <gibies@tropmet.res.in>:
>
>
> On 15 March 2011 10:31, gibies george <gibies@tropmet.res.in> wrote:
>>
>> Hello Malte,
>> There is a slight different way, which I am using.
>> We have
>>  u(time,lat,lon)
>>  v(time,lat,lon)
>> I combine them into another variable
>> data(time,lat,lon,component)
>> where
>> data&time = u&time   ; is also =v&time
>> data&lat = u&lat         ; is also =v&lat
>> data&lon = u&lon        ; is also =v&lon
>> data&component = (/"uwnd","vwnd"/)
>> data(time|:,lat|:,lon|:,component|0) = u(time|:,lat|:,lon|:)
>> data(time|:,lat|:,lon|:,component|1) = v(time|:,lat|:,lon|:)
>> Then find the EOF of the variable data.
>>
>> On 15 March 2011 01:56, Dennis Shea <shea@ucar.edu> wrote:
>>>
>>> Hello,
>>>
>>> D. S. Wilks
>>> Statistical Methods in the Atmospheric Sciences
>>> Academic Press (Elsevier), 2006
>>>
>>> pp 477-479:
>>>
>>> Section 11.2.2: Simultaneous PCA for Multiple Fields
>>>
>>> I would suggest you look at results from both the
>>> correlation and covariance matrices.
>>>
>>> Good luck
>>>
>>>
>>>
>>>
>>> On 03/14/2011 12:17 PM, Malte Stuecker wrote:
>>> > Hi everyone,
>>> >
>>> > I have done EOF analysis for scalar fields (e.g. SST) with the NCL EOF
>>> > functions, however I am struggling with the concept of how to do an
>>> > EOF analysis of vector data (e.g. analyzing the u- and v- component of
>>> > ocean current data at the same time). I understand that it is possible
>>> > to represent both quantities as a complex number, however I am not
>>> > sure about the practical (=programming) approach. Most literature that
>>> > I found seems to cover only the theory, but there are not many 'HOW TO
>>> > DO' sources out there.
>>> > My idea was to just combine the u and v fields in one matrix along one
>>> > of the spatial axis (e.g. combining a u (20E-40E,20S-20N) and v field
>>> > (20E-40E,20S-20N) to a (20E-40E,40S-40N) field), calculate the EOF and
>>> > afterwards split the eigenvector matrix into the u- and v- component
>>> > and plot the resulting vectors. In this case, is it possible to
>>> > interpret the eigenvalues + eigenvectors in the same way as you would
>>> > doing an EOF analysis on a scalar field? It would be great if anyone
>>> > could point me to some step-by-step introduction to this type of
>>> > problem or knows maybe some software packages other than NCL that
>>> > could deal with this type of analysis comfortably.
>>> > Thank you very much in advance!
>>> > _______________________________________________
>>> > ncl-talk mailing list
>>> > List instructions, subscriber options, unsubscribe:
>>> > http://mailman.ucar.edu/mailman/listinfo/ncl-talk
>>> _______________________________________________
>>> ncl-talk mailing list
>>> List instructions, subscriber options, unsubscribe:
>>> http://mailman.ucar.edu/mailman/listinfo/ncl-talk
>>
>>
>>
>> --
>> Gibies George,   CSIR-RF,
>> Seasonal Scale Prediction Group,
>> Climate and Global Modelling Division,
>> Indian Institute of Tropical Meteorology,
>> Dr. Homi Bhabha Road,
>> NCL (P. O.), Pashan,
>> Pune 411008, India.
>>
>> http://sites.google.com/site/gibiesge/
>>
>> Please Think about the environment. Save paper; Save Trees; and don't
>> print this e-mail unless it is necessary.
>
>
>
> --
> Gibies George,   CSIR-RF,
> Seasonal Scale Prediction Group,
> Climate and Global Modelling Division,
> Indian Institute of Tropical Meteorology,
> Dr. Homi Bhabha Road,
> NCL (P. O.), Pashan,
> Pune 411008, India.
>
> http://sites.google.com/site/gibiesge/
>
> Please Think about the environment. Save paper; Save Trees; and don't print
> this e-mail unless it is necessary.
>
_______________________________________________
ncl-talk mailing list
List instructions, subscriber options, unsubscribe:
http://mailman.ucar.edu/mailman/listinfo/ncl-talk
Received on Tue Mar 15 00:04:32 2011