# Re: Spectral amplitude as a function of latitude and frequency

From: Maria Gehne <mgehne_at_nyahnyahspammersnyahnyah>
Date: Fri Jun 28 2013 - 11:37:31 MDT

Hi Helen,

as far as I understand you want to know the frequency spectrum at each
latitude.

The function specx_anal takes a one dimensional array as its input. What
I would do
is compute the spectrum for each latitude separately using specx_anal
and save the amplitude
spec@spcx (which is a function of frequency only) for all latitudes in
an array that has size (#lats,#frequencies).

So something like this:

original array:
T(lat,time) with nlat and ntime entries

new array for spectra:
S(lat,frq) with nlat and ntime/2 entries and the entries for each lat l
are equal to:

do l=1,nlat
spec = specx_anal(T(l,:),iopt,jave,pt)
S(l,:) = spec@spcx
end do

You will probably have to add coordinate arrays for the latitude and
frequency coordinates, but you can get those from the original data
array and the specx_anal output.

You can then make a contour plot of S.

I hope this helps,

Maria

On 06/28/2013 03:43 AM, Parish, Helen wrote:
> I am trying to plot a contour of the amplitude of a spectrum (of e.g.temperature) as a function of latitude and frequency (for fixed altitude and longitude).
>
> I have used the function "specx_anal" prevously to give a simple x-y plot of magnitude versus frequency. (The magnitude and frequency are given as arrays which are attributes of specx_anal).
>
> Does anyone know how to get this to plot as a contour of magnitude versus frequency and latitude ?. I could not see any examples which create this kind of plot. I suppose what I need to plot is spec@spcx(latitude,spec@frq), but I am not sure how to configure the values into this form.
>
> I am wondering if anyone has any suggestions on how to do this, and whether specx_anal is the best function to use for this application, or whether there is a better way to make such a plot ?.
>
> Thank you.
> Helen.
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Maria Gehne
Postdoctoral Fellow
NCAR/CGD/CAS
P.O. Box 3000
Boulder, CO 80307
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Received on Fri Jun 28 11:37:42 2013

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