Hi Steffie, This would be similar to what is described here for creating a yearly time series; using either @AVE or another regridding transformationhttp://ferret.pmel.noaa.gov/Ferret/faq/averaging-to-regrid-a-time-series Except that you will want to define a seasonal axis instead of a yearly one. You can base one axis on the definition of an existing axis, taking every nth point, so starting with a monthly axis is an easy way to do this. If your incoming data already has a well-defined time axis, you can base it on that. Here's how that looks, using the dataset monthly_navy_winds that comes with the Ferret distribution: yes? use monthly_navy_winds yes? show grid uwnd GRID GDN1 name axis # pts start end subset FNOCX LONGITUDE 144mr 20E 17.5E(377.5) full FNOCY LATITUDE 73 r 90S 90N full normal Z TIME TIME 132 r 16-JAN-1982 20:00 17-DEC-1992 03:30 full ! Use the coordinate values of the time axis from the file to define a new time axis yes? let tt = t[gt=uwnd] yes? define axis/t/t0="`uwnd,return=t0`"/units="`uwnd,return=tunits`" time4 = tt[L=2:144:3] !-> define axis/t/t0="14-JAN-1980 14:00:00"/units="hour" time4 = tt[L=2:144:3] ! The original data: yes? list/t=1-jan-1982:1-jan-1983/x=180/y=0 uwnd VARIABLE : ZONAL WIND (M/S) FILENAME : monthly_navy_winds.cdf FILEPATH : /home/users/tmap/ferret/linux/fer_dsets/data/ SUBSET : 12 points (TIME) LONGITUDE: 180E LATITUDE : 0 180E 65 16-JAN-1982 / 1: -2.738 16-FEB-1982 / 2: -2.331 18-MAR-1982 / 3: -3.251 18-APR-1982 / 4: -3.124 18-MAY-1982 / 5: -1.818 18-JUN-1982 / 6: -2.007 18-JUL-1982 / 7: -0.367 17-AUG-1982 / 8: -0.900 17-SEP-1982 / 9: 3.223 17-OCT-1982 / 10: 2.167 17-NOV-1982 / 11: 2.875 17-DEC-1982 / 12: -0.007 ! The data on the seasonal axis: yes? list/t=1-jan-1982:1-jan-1983/x=180/y=0 uwnd[gt=time4@ave] VARIABLE : ZONAL WIND (M/S) regrid: 2192 hour on T@AVE FILENAME : monthly_navy_winds.cdf FILEPATH : /home/users/tmap/ferret/linux/fer_dsets/data/ SUBSET : 4 points (TIME) LONGITUDE: 180E LATITUDE : 0 180E 65 16-FEB-1982 / 1: -2.773 18-MAY-1982 / 2: -2.316 17-AUG-1982 / 3: 0.652 17-NOV-1982 / 4: 1.678 If you are reading data from a text file, then you'd first define the monthly time axis (See DEFINE AXIS) and a grid for the data, and set up to read the data as described here, and then define the seasonal axis as above. -Ansley On 11/19/2017 10:25 PM, Steffie Tom
wrote:
|