[ncl-talk] Some comments are needed in mjoclivar_14.ncl on the MJO diagnostics page [SEC=UNCLASSIFIED]

[Dennis Shea]

I will look into this when I get a chance.

Cheers
D

On Wed, Jul 26, 2017 at 9:03 AM, Carl Schreck <cjschrec at ncsu.edu> wrote:

> That's a great catch. The way I handle it is:
>
>   ; calculate the PCs
>   retVal = eofunc_ts_Wrap( data(var|:,lon|:,time|:), eof, False )
>
>   do e = 0, nEof-1
>     retVal(e,:) = ( retVal(e,:) + retVal at ts_mean(e) ) / pcStddev(e)
>   end do
>
> Where pcStddev is the standard deviation calculated from the original PCs
> over a 30+ year period.
>
> It would be great if eofunc_ts had an option to not subtract the mean
> automatically.
>
> Carl
>
> On Tue, Jul 25, 2017 at 12:34 AM, Eun-Pa Lim <eun-pa.lim at bom.gov.au>
> wrote:
>
>> ​Dear NCL developers
>>
>>
>> My colleagues Harry Hendon and Abhik  Santra at the Bureau of Meteorology
>> want to report an issue regarding the computation of the RMM1 and RMM2 time
>> series (eof_ts_cdata) and the expansion coefficients of olr, u200 and u850
>> (ceof_ts) in mjoclivar_14.ncl.
>>
>> ​> eof_ts_cdata = eofunc_ts(cdata,eof_cdata,False)
>>
>> Harry and Abhik were trying to replace cdata with forecast data of
>> a particular year to see if forecast amplitudes of RMM1 and RMM2 are
>> realistic or not.
>>
>> Because eofunc_ts_Wrap removes the time mean of the input data by default
>> (i.e. 1-year time mean of forecast data for their case), their forecast MJO
>> amplitudes were systematically biased.
>>
>>
>> This problem will occur when people try to compute the MJO amplitues with
>> a subset of a dataset.
>>
>>
>> Could you please add a comment where eof_ts_cdata and ceof_ts appear in
>> mjoclivar_14.ncl that users should compute the expansion coefficients
>> manually rather than using eofunc_ts_Wrap if the removal of the time mean
>> of the input data is not intended/desirable?
>>
>>
>> Please let me know if what I've explained is not clear.
>>
>>
>> Many thanks!
>>
>>
>> Eun-Pa
>>
>>
>> Research Scientist
>>
>> The Australian Bureau of Meteorology
>>
>> GPO Box 1289, Melbourne, VIC 3000, AUS
>>
>>
>>
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>>
>
>
> --
>
>
> <https://ncics.org/>
> * Cyclone <http://www.cyclonecenter.org/>*Center.org
> <http://www.cyclonecenter.org/>   *Carl J. Schreck III, PhD*
> *Research Scholar / Research **Assistant Professor*
> Cooperative Institute for Climate and Satellites NC (CICS
> <http://www.cicsnc.org/>*-NC) <http://www.cicsnc.org/> /*
> Department of Marine, Earth, and Atmospheric Sciences (MEAS)
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