Help plotting netcdf files with gmt5

Q&A
1

Hello
I hope you can help. I have moved from GMT4.5 to GMT 5 and I am trying to plot netcdf file - see the ncdump - the variable ‘thk’.
I have never tried to plot a netcdf before.

I am using this grdimage command:
grdimage -V ./GRD/thk_422.nc -R0/2000/0/2000 -JX10/10 -Ba10 -C./CPT/ice_ais.cpt -O -K >> PLOT/ICE.ps

However when I plot, I get an error message that the grid been outside
grdimage: Allocates memory and read data file ./GRD/thk_422.nc
grdimage: Your grid y’s or latitudes appear to be outside the map region and will be skipped.
grdimage: No grid or image inside plot domain

any help would be great
ncdump information: netcdf thk_422 {
dimensions:
y1 = 1929 ;
x1 = 1571 ;
variables:
double thk(y1, x1) ;
thk:units = “meter” ;
thk:long_name = “ice thickness” ;
thk:standard_name = “land_ice_thickness” ;
thk:_FillValue = 1.e+20 ;
thk:missing_value = 1.e+20 ;
thk:cell_methods = “time: mean” ;
double x1(x1) ;
x1:units = “meter” ;
x1:long_name = “Cartesian x-coordinate” ;
x1:axis = “X” ;
double y1(y1) ;
y1:units = “meter” ;
y1:long_name = “Cartesian y-coordinate” ;
y1:axis = “Y” ;

// global attributes:
:Conventions = “CF-1.3” ;
:title = “” ;
:institution = “” ;
:source = “” ;
:history = “Mon Jan 25 12:07:18 2021: ncwa -a time thk_422_B.nc thk_422_C.nc\n”,
“Mon Jan 25 12:05:08 2021: ncks -C -O -x -vtime thk_422.nc thk_422_B.nc\n”,
“Tue Jan 19 18:07:05 2021: ncks -vthk TG-NAIS-cb1-96201207.cism.h.0422-01-01-00000.nc thk_422.nc\n”,
“” ;
:references = “” ;
:comment = “” ;
:configuration = “” ;
:cesmYMD = 4220101 ;
:cesmTOD = 0 ;
:glcYMD = 4220101 ;
:glcTOD = 0 ;
:elapsed_days = 150015 ;
:time_period_freq = “year_1” ;
:model_doi_url = “https://doi.org/10.5065/D67H1H0V” ;
:NCO = "“4.6.0"” ;
:nco_openmp_thread_number = 1 ;

2

Why?
In GMT6 you could just do (and maybe in GMT5 maybe too but we don’t use it anymore)

grdimage -V ./GRD/thk_422.nc -Ba -C./CPT/ice_ais.cpt ...
3

Hi Joaquim

The computer I work on only has gmt5.4.3 - the version I use is really out of my control

This is the command that I thought would work - just as you type.

Sarah

4

OK, the error message is saying that the -R limits do not fit with the grid coordinates. In these cases you should use grdinfo instead of looking at the output of ncdump

5

Thanks for the tip. I had totally forgotten about grdinfo

This gives me a totally different set of limits. : larger than what I was adding for -R.
I think this will do the trick!

Sarah