Re: [ferret_users] How to plot Monthly Global dataset of singlevariable?

[Jaison Kurian <jaison@xxxxxxxxxxxxxxxxxx>]

Hi Ashley,
      Your dataset appears to be 3 dimensional. You tried to read
the data on to a 2D grid (X & T) first and then RESHAPE'd it on
to a 3D grid. If you know the exact lat/lon/time coordinates of
the dataset, you can directly read data onto the destination grid
consisting of these coordinate axes. Proceed as shown below. It is
a better to name the axes beginning with the letter representing that
dimension (ie. x_binary is a better axis name than binary_x).
While defining time axis, it is always better to use "DAYS" as
time units (if possible). For a monthly time axis, you can set the
time increment as `365.2425/12`. This will get rid of the warning
message.

Let me know if you face any problems. Sometimes you have to flip
the Y-axis. First you proceed as shown below. Get the plot and
see whether it is OK.

Regards,

Jaison


!------------------------------------------------------------------------------
     cancel reg/all ; cancel data/all
     set memory/size=80

     define axis/x=0.5:359.5:1/units=longitudes xlon  ! MODULO stuff will be
                                                      ! taken careoff
     define axis/y=-89.5:89.5:1/units=latitudes ylat
     define axis/t=15-DEC-1981:14-FEB-2003:`365.2425/12`/\
                      units=days/T0=31-DEC-1980 time

     ! suppose you want to check howmany points are there along
     ! each axes then

     SAY "   X-Axis xlon have `x[gx=xlon],r=iend`  points"
     SAY "   Y-Axis ylat have `y[gy=ylat],r=jend`  points"
     SAY "   T-Axis time have `t[gt=time],r=lend`  points"

     ! Now define a grid using these axes

     define grid/x=xlon/y=ylat/t=time gbin

     ! Open/Read the binary file and set the missing value

     FILE/FORMAT=stream/grid=gbin/var=sst/title="OI SST" OISST_198112_200302

     set var/bad=-999.99  ! give proper missing value here

     set reg/t=15-JAN-1982

     FILL/lev=(-5,30,1) sst
     go land

!----------------------------------------------------------------------------

On Thu, 6 Jul 2006, Ashley Watson wrote:

> Hi all,
>     I have monthly global dataset  of  255 months  from  198112 to 200302
> . ( file size 66096000 bytes ). I read the data with the following commands.
> I think there is no problem in reading the data.
>
>
> Set memory/size=80
> DEFINE AXIS/X=1:`360*180`:1 binary_x
> DEFINE AXIS/T=1:255:1 binary_t
> DEFINE GRID/X=binary_x/T=binary_t binary_g
> FILE/FORMAT=stream/G=binary_g/VAR=sst OISST_198112_200302
>
>
> Then I worked to define the grid for data according to section 4.1.3 of
> Chapter 2.
>
> DEFINE AXIS/MODULO/X=0.5:359.5:1 onedeg_x
> DEFINE AXIS/Y=-89.5:89.5:1 onedeg_y
> DEFINE AXIS/T=15-Dec-1981:15-Feb-2003:1/UNITS=month month_t
> DEFINE GRID/X=onedeg_x/Y=onedeg_y/T=month_t onedeg_g
> LET dummy = x[GX=onedeg_g] + y[GY=onedeg_g] + t[GT=onedeg_g]
> LET field = RESHAPE(sst[i=1:`360*180`],dummy)
>
> I got following message while defining time axis,
>
> *** NOTE: /UNIT=MONTHS is ambiguous ... using 1/12 of 365.2425 days
>
> I tried "shade sst[l=1] " but got the error
> **ERROR: dimensions improperly specified: must be a 2D region
>
> I dont understand how to view my data with shade/fill  commnad after these
> steps.
> Looking forward for help.
>
> Ashley