Re: [ferret_users] interannual standard deviation

[Ryo Furue <furue@xxxxxxxxxx>]

Dear Ruksana,

> let mean = data[x=@sum]/data[x=@ngd]

Ferret automatically does this for you with

data[x=@AVE]

that is, the averaging operation automatically excludes "bad" points.

> Now, I would like to map the interannual standard deviation.

To do so, you first calculate a climatological annual cycle.  I think
there is a nice entry in the official FAQ of Ferret.  Also you'll find
some discussion in the archive of this mailing list.  The keyword to
search with is "climatology".

Once you have obtained a climatological annual cycle that repeats
itself forever, the interannual anomaly is

let anom = data - clim

then you calculate the standard deviation of "anom", perhaps using the
operator @STD as in anom[t=@STD] or using the method you showed in
your previous email message.

If your time axis is not uniform, however, I don't know whether @STD
works correctly or not.

Regards,
Ryo