Dennis Shea shea at ucar.edu
Fri Feb 18 15:36:11 MST 2022

```*https://www.ncl.ucar.edu/Applications/fouranal.shtml*
<https://www.ncl.ucar.edu/Applications/fouranal.shtml>

See the example*. fanal_4.ncl ...* in particular, the figure.

The phase component gives the index (subscript) of the maxima.

(*1*,0)	72         <=== Phases: *location of first maximum*
(*1*,1)	36
(*1*,2)	12
for 'latitude', then the first maxima occur at
finfo(1,lat(72)), finfo(1,lat(36)), finfo(1,lat(12))

If this were 'time', then the first maxima occur at
finfo(1,time(72)), finfo(1,time(36)), finfo(1,time(12))

On Thu, Feb 17, 2022 at 7:42 AM Lyndz via ncl-talk <
ncl-talk at mailman.ucar.edu> wrote:

> Dear NCL-experts,
>
> I am using the *fourier_info *to extract the amplitude of the first and
> second harmonics of a 24 time series (
> https://www.ncl.ucar.edu/Document/Functions/Built-in/fourier_info.shtml)
>
> *;[time | 24] x [lon | 42] x [lat | 68]*
>
> *finfo_pa = fourier_info(pa(lon|:,lat|:,time|:),2,1.)*
>
> But, I am only getting the amplitude, phase, and variance explained from
> the output.
>
> How can I extract the specific time/s (for first harmonics, it is one
> time, for the 2nd harmonic it is two) when the wave reaches its peak (or
> the time when I got the amplitude) for the first and second harmonics?
>
> I'll appreciate any help on this.
>
> Sincerely,
> Lyndz
>
>
>
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