Hi Yun,
Are you using an older version of Ferret? In Ferret versions prior to
version 5.7, when Ferret was used to write data with an
irregularly-spaced time axis, it issues this warning, as discussed in
the email archives that Jaison pointed out. With more recent versions
of Ferret, the default behavior is to write the time axis coordinates
and also the bounds which describe the irregular grid boxes, and this
allows the axis to later be appended to. The newer behavior is
described in this edition of the Ferret Release notes, scroll down to
the section about writing files.
http://ferret.pmel.noaa.gov/Ferret/Documentation/Release_Notes/v57.html#nc_bounds
If you can, I would suggest upgrading to a more recent version of
Ferret. But also, note that what you did is all right. Your file is
being written, and it is correct, but if you tried to append more time
steps to it, the bounds of the boxes might not be correct. The lines
Ferret writes are simply a warning, they do not indicate an error, but
are only telling you that the size of the grid boxes are not saved in
the file.
Here is a script and the output file written with Ferret v6.0 similar
to what's in the Users List archive message; the command ncdump used to
look inside the file. See how the "bounds" are written for the
irregular time axis.
yes? define axis/t/units=days/t0=1-jan-2001 t_out =
{15,45,73,104,134,165,195,226,227,287,318,348}
yes? let timestamp = t[gt=t_out] * 0
yes? let v = timestamp + 6
yes? save/file=aa.nc/clobber v
yes? sp ncdump -h aa.nc
netcdf aa {
dimensions:
T_OUT = UNLIMITED ; // (12 currently)
bnds = 2 ;
variables:
double T_OUT(T_OUT) ;
T_OUT:units = "DAYS since 2001-01-01 00:00:00" ;
T_OUT:time_origin = "1-JAN-2001" ;
T_OUT:axis = "T" ;
T_OUT:bounds = "T_OUT_bnds" ;
double T_OUT_bnds(T_OUT, bnds) ;
float AA(T_OUT) ;
AA:missing_value = -9.9999998e+33f ;
AA:_FillValue = -9.9999998e+33f ;
AA:long_name = "TIMESTAMP + 6" ;
// global attributes:
:history = "FERRET V6 21-Nov-06" ;
data:
T_OUT = 15, 45, 73, 104, 134, 165, 195, 226, 227, 287, 318, 348 ;
T_OUT_bnds =
0, 30,
30, 59,
59, 88.5,
88.5, 119,
119, 149.5,
149.5, 180,
180, 210.5,
210.5, 226.5,
226.5, 257,
257, 302.5,
302.5, 333,
333, 363 ;
AA = 6 , 6 , 6 , 6 , 6 , 6 , 6 , 6 , 6 , 6 , 6 , 6 ;
}
--------
If you wrote the same variable with Ferret v5.51, the bounds are not
written but the data is present and the axis is correct, but you would
need to be careful if you want to append more time steps.
ncdump aa_551.nc
netcdf aa_551 {
dimensions:
T_OUT = UNLIMITED ; // (12 currently)
variables:
double T_OUT(T_OUT) ;
T_OUT:units = "DAYS since 2001-01-01 00:00:00" ;
T_OUT:time_origin = "1-JAN-2001" ;
float V(T_OUT) ;
V:missing_value = -9.9999998e+33f ;
V:_FillValue = -9.9999998e+33f ;
V:long_name = "TIMESTAMP + 6" ;
// global attributes:
:history = "FERRET V5.51 21-Nov-06" ;
data:
T_OUT = 15, 45, 73, 104, 134, 165, 195, 226, 227, 287, 318,
348 ;
V = 6 , 6 , 6 , 6 , 6 , 6 , 6 , 6 , 6 , 6 , 6 , 6 ;
}
Yun.Li@csiro.au wrote:
Dear Ferret
users,
I am trying
to extract NCEP u wind at height
850mb using the following lines. But I can not save u850.mon.nc
properly,
which contains warning message as follows.
Can you
please give me a help on how to
save u850.mon.nc correctly?
Many thanks,
Yun Li
CSIRO, Australia
#######
yes? use
uwnd.mon.mean.nc
yes? SET
MEMORY/SIZE=50
!Cached
data cleared from memory
yes? let
u850 = uwnd[d=1, k=15]
yes? set
var/title="Monthly mean u850
wind (m/s)" u850
yes?
save/CLOBBER/file=u850.mon.nc u850
LISTing to
file u850.mon.nc
*** NOTE:
Irregular T axis box
limits cannot be saved
*** NOTE:
in NetCDF files created by
this means.
*** NOTE:
To avoid this create the
file using the qualifiers
***
NOTE:
/RIGID/HEADING=ENHANCED/LLIMITS=lo:hi
*** NOTE:
This warning will not be
repeated.
yes?
--
~> ~> ~> ~> ~> ~> ~> ~> ~> ~> ~>
Ansley Manke, NOAA/PMEL ansley.b.manke@noaa.gov
7600 Sand Point Way NE, Seattle WA
Phone 206-526-6246, FAX 206-526-6744
|