# [ncl-talk] remove seasonal data

Will Hobbs will.hobbs at utas.edu.au
Sun Apr 11 17:34:02 MDT 2021

```Hi Sri

To me, your question doesn’t make a whole lot of sense, since typically the annual cycle is expressed as the long-term mean of each individual day/month/season (depending on the temporal resolution of the data).

I guess if you really want to keep the climatological annual mean, I can think of two ways of doing it:

1.  Calculate the long-term mean (over the whole dataset), remove the annual cycle using rmMonAnnCycLLT(), and then add the long-term mean back onto the data

>mn = dim_avg(data)
>anom= rmMonAnnCycLLT(data)
>anom = anom + conform(anom,mn, (/0,1/))

1.  Estimate a 12-month cycle using fourier_info()., and remove that from the 12-momth harmonic from the data.

Will

From: ncl-talk <ncl-talk-bounces at mailman.ucar.edu> on behalf of Sri nandini via ncl-talk <ncl-talk at mailman.ucar.edu>
Reply to: Sri nandini <bax8609 at uni-hamburg.de>
Date: Friday, 9 April 2021 at 10:21 pm
To: Ncl-talk <ncl-talk at ucar.edu>
Subject: [ncl-talk] remove seasonal data

Hello dear ncl-users,

Could someone tell me if there is a function in NCL that only removes
seasonal (Annual cycle) data from monthly data?

The function: rmMonAnnCycLLT removes the annual cycle from monthly
(number of months = 12) data and subtracts the long-term means from each
month. But i do not want to get anomalies by subtracting the long term
means. I only want to calculate and remove the seasonal aspect (the
Annual cycle).

Thanx

Sri

--
Dr. Sri, Nandini-Weiss
Research Associate

Universität Hamburg
Center for Earth System Research and Sustainability (CEN)
Cluster of Excellence 'Climate, Climatic Change, and Society' (CLICCS)

Bundesstrasse 53, 20146 Hamburg

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