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mean or cumul on time axis



Hello!

I need some help to regrid data on time. I have 6-hourly precipitation values and I'd like to have the cumul and the mean on 1 day. I have tried by defining a new time axis and regridding the data using gt=my_new_time_axis@sum and @ave. Ferret obviously computes something, the time axis of my new variable is correct, but I'm a bit perplex about the results Ferret gives me.

Here is an example with a dummy variable.

yes? list var
SUBSET : 13 points (TIME)
01-SEP-1993 00:00 / 1: 1.00
01-SEP-1993 06:00 / 2: 2.00
01-SEP-1993 12:00 / 3: 3.00
01-SEP-1993 18:00 / 4: 4.00
02-SEP-1993 00:00 / 5: 5.00
02-SEP-1993 06:00 / 6: 6.00
02-SEP-1993 12:00 / 7: 7.00
02-SEP-1993 18:00 / 8: 8.00
03-SEP-1993 00:00 / 9: 9.00
03-SEP-1993 06:00 / 10: 10.00
03-SEP-1993 12:00 / 11: 11.00
03-SEP-1993 18:00 / 12: 12.00
04-SEP-1993 00:00 / 13: 13.00

yes? define axis/t="01-SEP-1993 00:00":"4-SEP-1993 00:00":12/units=hours t12h
yes? let var12h = var[gt=t12h@ave]
yes? list var12h
VARIABLE : VAR[GT=T12H@AVE]
SUBSET : 7 points (TIME)
01-SEP-1993 00:00 / 1: 1.000
01-SEP-1993 12:00 / 2: 2.000
02-SEP-1993 00:00 / 3: 3.000
02-SEP-1993 12:00 / 4: 4.000
03-SEP-1993 00:00 / 5: 5.000
03-SEP-1993 12:00 / 6: 6.000
04-SEP-1993 00:00 / 7: 7.000

yes? define axis/t="01-SEP-1993 00:00":"4-SEP-1993 00:00":1/units=days t1d
yes? let var1d = var[gt=t1d@ave]
yes? list var1d
VARIABLE : VAR[GT=T1D@AVE]
SUBSET : 4 points (TIME)
01-SEP-1993 00 / 1: 1.333
02-SEP-1993 00 / 2: 3.000
03-SEP-1993 00 / 3: 5.000
04-SEP-1993 00 / 4: 6.667

yes? define axis/t="01-SEP-1993 00:00":"4-SEP-1993 00:00":12/units=hours t12h
yes? let var12h = var[gt=t12h@sum]
yes? list var12h
VARIABLE : VAR[GT=T12H@SUM]
SUBSET : 7 points (TIME)
01-SEP-1993 00:00 / 1: 1.000
01-SEP-1993 12:00 / 2: 2.000
02-SEP-1993 00:00 / 3: 3.000
02-SEP-1993 12:00 / 4: 4.000
03-SEP-1993 00:00 / 5: 5.000
03-SEP-1993 12:00 / 6: 6.000
04-SEP-1993 00:00 / 7: 7.000

yes? define axis/t="01-SEP-1993 00:00":"4-SEP-1993 00:00":1/units=days t1d
yes? let var1d = var[gt=t1d@sum]
yes? list var1d
VARIABLE : VAR[GT=T1D@SUM]
SUBSET : 4 points (TIME)
01-SEP-1993 00 / 1: 2.00
02-SEP-1993 00 / 2: 6.00
03-SEP-1993 00 / 3: 10.00
04-SEP-1993 00 / 4: 10.00
yes?

Where am I wrong?

Thanks for any clue!

Emilie

____________________________________________________________
Emilie VANVYVE
Physicist, PhD student

Université catholique de Louvain (UCL)
Institut d'astronomie et de géophysique G. Lemaître (ASTR)
Chemin du Cyclotron, 2
1348 Louvain-la-Neuve (Belgium)
Phone : +32-(0)10-473300
Fax : +32-(0)10-474722
E-mail : vanvyve@astr.ucl.ac.be
Web : www.astr.ucl.ac.be

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