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Re: your mail : 360_DAY calendar & climatology
Hi Wendy Wang,
Time axis is always a concern. Ferret needs the source
(your variable) and destination (climatological time axis) time axis
to be defined over the same calendar type to do "MODULO" regridding.
>From the error message you have got it is clear that your variable is
on a "360_DAY" calendar. But the "month_reg" defined in climatological_
axes.cdf is "GREGORIAN". So the better way to get the climatology is to
define a "360_DAY" climatological axis. If you want more details about
the calendar types/attributes inf Ferret/NetCDF please have look at
Ferret user manual : Ch4 Sec2.2. Time axes and calendars.
How to decide the calendar type of your variable in NetCDF file ?
There are two ways
1. open the dataset in Ferret and use RETURN (will work with
only the recent versions of Ferret..i think)
yes? use SWmn.nc
yes? say `chl,RETURN=calendar`
2. use netcdf utility "ncdump" to see the time axis definition
[wendy@wendysmachine]$ ncdump -h SWmn.nc | more
look for the "calendar" attribute. Please remember that
if there is no calendar attribute in your NetCDF file,
Ferret will take it as "GREGORIAN" calendar.
The example below illustrates the method to find climatology by
defining a "climatological time axis" with proper /CALENDAR qualifier.
If you have any doubts/problems please let me know.
Hope This Helps
With Regards
Jaison
!----example.jnl-----------------------
\ cancel mode verify
! create a variable "var" defined on a "360_DAY" (monthly) calendar axis
define axis/t="16-JAN-1990:00":"16-DEC-1994":`360/12`/units=days/\
calendar=360_DAY/T0="30-DEC-1989:00" tax
let var = t[gt=tax]
say `var,r=calendar`
! define a proper climatological(monthly) axis
define axis/t="16-JAN-0001:00":"16-DEC-0001":`360/12`/units=days/\
calendar=360_DAY/T0="30-DEC-0000:00"/MODULO tclim
let var_clim = var[gt=tclim@MOD] ! get the climatology
list var_clim
!---end of example.jnl-------------------------------
On Mon, 20 Dec 2004, Wendy Wang wrote:
> Hi Ferret_users,
>
> I try to do monthly climatology of chlorophyll from >6 years monthly means.
>
> 16-SEP-1997 / 1: ....
> 16-OCT-1997 / 2: 0.1552
> 16-NOV-1997 / 3: 0.0511
> 16-DEC-1997 / 4: 0.0636
> .
> .
> 16-NOV-2003 / 75: 0.1932
> 16-DEC-2003 / 76: 0.1704
>
> But I got the following error:
>
> yes? use SWmn.nc
> yes? USE climatological_axes
> *** NOTE: regarding /cdisk/d9/wwang/FERRET/go/climatological_axes.cdf ...
> *** NOTE: Climatological axes SEASONAL_REG, MONTH_REG, and MONTH_IRREG
> defined
> yes? CANCEL DATA climatological_axes
> yes? let cl_time=chl[t=16-jan-1998:16-dec-2003]
> yes? let clm=cl_time[gt=month_reg@mod]
> yes? list/x=140w/y=0 clm
> **ERROR: regridding: only @ASN, @LIN, or @NRST regridding between
> calendar types: 360_DAY, GREGORIAN
>
> Could someone tell me where the problem is? Thanks.
>
> Wendy Wang
>
--
___________________________________________________
Jaison Kurian
Centre for Atmospheric and Oceanic Sciences
Indian Institute of Science
B A N G A L O R E 560 012
Ph: +91-80-3942505
+91-80-3600450
Fax:+91-80-3600865
___________________________________________________
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