Thanks Ansley,
My problem is now nearly solved based on your guidance, with some more refinements for z axis.
In fact, for z axis, I would like to have pressure unit, instead of level unit.
In the example nc file, there is a variable called pres that is actual depth in decibar.
The problem is that pres varies on time (N_PROF), as well as on level (N_LEVELS) as follows:
yes? use/order=ZT 2900623_prof.nc
yes? sh grid pres
GRID GJV4
name axis # pts start end
normal X
normal Y
N_LEVELS Z 48 r 1 48
N_PROF T 35 r 1 35
How can I have temp on z-axis with actuall pressure unit, instead of level unit.
Thanks in advance,
Chan Joo
--------------------------------------- [ Original Message ] --------------------------------------
Sender : Ansley Manke < Ansley.B.Manke@xxxxxxxx >
To : Chan Joo Jang < cjjang@xxxxxxxxxxx >
CC : oar.pmel.ferret_users@xxxxxxxx
Date : 2007-12-15 08:27:10
S u b j e c t : Re: [ferret_users] change axis
Hi,
Thanks for the example file. Ferret has some tools to deal with this kind of profile data. As you found, if we just point to the data, it's on a grid that doesn't make sense:
yes? USE argo2900623_prof.ncThe attributes in the file don't give Ferret enough information to know that N_LEVELS should be a Z axis and N_PROF should be a T axis. We can use the /ORDER qualifier to force the correct directions to be used:
yes? SHOW GRID temp
GRID GAI4
name axis # pts start end
N_LEVELS X 48 r 1 48
N_PROF Y 35 r 1 35
normal Z
normal T
yes? CANCEL DATA/ALLNow, we'd like to use the variable JULD to define a time axis. In files like this, sometimes the times are not in monotonically increasing order, and so we would need to sort them. I'll come back to this. In this file, the times are monotonically increasing, so we can just use them as is.
yes? USE/ORDER=ZT
yes? SHOW GRID temp
GRID GAI4
name axis # pts start end
normal X
normal Y
N_LEVELS Z 48 r 1 48
N_PROF T 35 r 1 35
! this gives us the units and time origin.
yes? LIST juld.units
"days since 1950-01-01 00:00:00 UTC"
! Define a time axis based on JULD
yes? DEFINE AXIS/T/T0="1-jan-1950:00:00"/UNITS=days tday = juld
! Also define a new Z axis. This is ocean data, so it should
! be increasing downwards. First define zz, a variable containing
! the levels, then define an axis from that variable.
yes? LET zz = z[gz=temp]
yes? DEFINE AXIS/Z/UNITS=levels/DEPTH zlev = zz
! Now define a new variable on these corrected axes,
! using the @ASN transformation to just put them onto
! the new axes. Keep the units and title from TEMP.
yes? LET/UNITS="`temp,RETURN=units`"/\
TITLE="`temp,RETURN=title`" \
temperature = temp[GZ=zlev@ASN, GT=tday@ASN]! Now the variable is on the correct ZT grid,If the JULD variable were not monotonic, we would need to SORT the variable JULD, and use the result to both define the new time axis and also to reorder TEMP in T before assigning it to the new T axis.
! For example, we can do these things:
yes? plot/L=1 temperature
yes? shade temperature
Ansley
Chan Joo Jang wrote:Hi Ferr users,
I got ARGO float data files from http://www.usgodae.org/cgi-bin/argo_select.pl .
(One of those nc files is attached for your reference.)
Using some functions such as RESHAPE, I tried to change original axis (n_prof, n_levels) to (time, depth) of TEMP (temperature), without any success.
In other words, I want to have TEMP(julian day, pres) instead of TEMP(n_prof, n_levels). All informations for julian day(juld) and depth (pres) are in the nc files.
Any ideas or suggestions would be welcome.
oceanboy
=======
PS) Some parts of ncdump output are as follows:
netcdf 2900623_prof {
dimensions:
DATE_TIME = 14 ;
STRING256 = 256 ;
STRING64 = 64 ;
STRING32 = 32 ;
STRING16 = 16 ;
STRING8 = 8 ;
STRING4 = 4 ;
STRING2 = 2 ;
N_PROF = 35 ;
N_PARAM = 3 ;
N_LEVELS = 48 ;
N_CALIB = 1 ;
N_HISTORY = UNLIMITED ; // (0 currently)
variables:
float PRES(N_PROF, N_LEVELS) ;
PRES:long_name = "SEA PRESSURE" ;
PRES:_FillValue = 99999.f ;
PRES:units = "decibar" ;
PRES:valid_min = 0.f ;
PRES:valid_max = 12000.f ;
PRES:comment = "In situ measurement, sea surface = 0" ;
PRES:C_format = "%7.1f" ;
PRES:FORTRAN_format = "F7.1" ;
PRES:resolution = 0.1f ;
float TEMP(N_PROF, N_LEVELS) ;
TEMP:long_name = "SEA TEMPERATURE IN SITU ITS-90 SCALE" ;
TEMP:_FillValue = 99999.f ;
TEMP:units = "degree_Celsius" ;
TEMP:valid_min = -2.f ;
TEMP:valid_max = 40.f ;
TEMP:comment = "In situ measurement" ;
TEMP:C_format = "%9.3f" ;
TEMP:FORTRAN_format = "F9.3" ;
TEMP:resolution = 0.001f ;
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Currently at Dep. of Oceanography, Texas A&M Univ
Chan Joo Jang, Ph.D., researcher
Korea Ocean Research and Development Institute
1270 Sa2-dong, SangRok-gu, Ansan 426-744, Korea
Tel: +82-31-400-6317 Fax: +82-31-408-5827
cjjang@xxxxxxxxxxx, http://ogcm.kordi.re.kr
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