Re: [ferret_users] Remove seasonal cycles from daily data sets

[Ansley Manke <ansley.b.manke@xxxxxxxx>]

Hi Peng,
First you will need to make a dataset which lets Ferret see your data on a single multiple-year time axis. This can be done with a descriptor file. See the notes about descriptor files in the documentation: http://ferret.pmel.noaa.gov/Ferret/documentation/users-guide/converting-to-netcdf/CREATING-A-MULTI-FILE-NETCDF-DATA-SET

and here is how to create a descriptor file:
http://ferret.pmel.noaa.gov/Ferret/documentation/users-guide/converting-to-netcdf/CREATING-A-MULTI-FILE-NETCDF-DATA-SET#_VPINDEXENTRY_1144

Then to remove the seasonal cyele it will be a simple matter of computing the seasonal signal.  If your descriptor file is called data_1993_2004.des, and it contains a variable called "var",  then this would go something like this:

yes? set data data_1993_2004.des
yes? let var_season = var[gt=seasonal_reg@mod]

yes? let var_anomoly = var - var_season

Ge Peng wrote:

Dear Ferret Users,

Does anyone know how to remove seasonal cycles from a daily data set?

My data set is on a regular grid (144x90) and contains daily averages from
Jan 1, 1993 to Dec 31, 2004. The variables are archived yearly (one file
per year.) Thus, the record length for each file is either 365 or 366.

Thanks in advance,

--- Peng