Re: Spectral analysis: variance per month?

From: Dennis Shea <shea_at_nyahnyahspammersnyahnyah>
Date: Tue Aug 30 2011 - 13:40:44 MDT

Hi Maurice,

You are not being ignored. I sent your question to
Rich Neale. He may be off-site at a mtg.

My guess ...

The rhs histogram plots for say January were created via

      var = (1/N)*(xjan(n)-xJAN)^2 maybe (1/[N-1]) rather than 1/N

      where xJAN is the overall January mean and xjan are the individual
      January monthly means ....

I am sure the data used in the spectrum were detrended and tapered.

I would suggest that the time series of monthly (?) values be detrended
before doin any calculations. (a) detrend the whole time series;
(b) taper (a) and compute the spectrum; (c) calculate the individual
monthly variances for histogram

On 08/30/2011 09:49 AM, wrote:
> Good morning all,
> I am going to perform a spectral analysis on model output and would like to see spectral variance per month in addition to variance per period.
> For an example of what I attempting to produce please see the rightmost element of the attached figure, where variance (K^2/month) is depicted on a monthly basis. This screenshot was captured from slide 3 in
> How can I use NCL to reconstruct variance on a per month basis, in addition to the more traditional: "variance per spectral frequency" which is the default output from NCL's spectral analysis function?
> Many thanks,
> Maurice
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Dennis J. Shea                  tel: 303-497-1361    |
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Received on Tue Aug 30 13:40:49 2011

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