[ncl-talk] How to get explained variance from spectra

[Lyndz]

Thanks Sir Dennis!

-Lyndz

On Fri, Sep 17, 2021 at 10:39 AM Dennis Shea <shea at ucar.edu> wrote:

> As notes in the *specx_anal*
> <http://www.ncl.ucar.edu/Document/Functions/Built-in/specx_anal.shtml>
> documentation:
> -====
>
> These spectra have been normalized so that the area under the curve:
>
> (*spcx*(0)+*spcx*(*N*/2-1))*(df/2) + SUM{*spcx*(1:N/2-2)*df}
>
> equals the variance of the detrended series, where df=(1/*N*)=frequency
> spacing.
>
> The units are variance/(unit frequency interval).
>
> ====
>
> You know the frequencies corresponding to  5-to-10 days.
>
>
> 5-to-10day variance:   var_510 = SUM{*spcx*('f5->f10')*df}
>
>
> fractional_variance = var_510/total_variance
>
>
>
>
> On Thu, Sep 16, 2021 at 2:39 AM Lyndz via ncl-talk <
> ncl-talk at mailman.ucar.edu> wrote:
>
>> Dear NCL-experts,
>>
>> I have a sample data that I attached here and below is the script that I
>> used to plot the spectra.
>>
>> I found significant peaks between 5-10 (days).
>>
>> I would like to ask how to estimate the fractional variance of
>> total rainfall variability explained by this 5-10 days ISO. Im not sure if
>> this can be estimated from the spectra. If not, any suggestions on how to
>> do this NCL?
>>
>>
>> -Lyndz
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>
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