[ncl-talk] metadata for netCDF file

[Mary Haley]

Mark,

1) You can do it directly on the variable on the file, as long as you open
the file in "w" mode when you call addfile:

a = addfile("......","w")
a->tas at coordinates = "lon lat height"

2) and 3) can be answered together. Whenever NCL writes variables to a
NetCDF file, it *always* forces variables to have a dimension name, even
scalars. If you don't provide a name when you write the variable to a
NetCDF file using NCL, then NCL will assign names "ncl1", "ncl2", "ncl3",
etc.

When writing scalar variables to a file, we recommend using "ncl_scalar" as
a dimension name:

p0 =1000.
p0!0 = "ncl_scalar"
a->p0 = p0

For variables containing characters, like your rotated pole variable, it's
up to you to decide on a dimension name. ou might want to use something
that indicates a string length, like "nchar":

a->rotated_pole!0 = "nchar"

--Mary


On Thu, Dec 4, 2014 at 12:42 PM, Mark Chan <cym263 at yahoo.com> wrote:
>
> Dear NCL users,
>
> In the below is about the metadata of a netCDF file, generated by using
> NCL script. I would like to do some modification about the metadata. Can
> one give any suggestion how to do it?
>
> (1) modifying the coordinates from (tas:coordinates = "lon lat") to
> (tas:coordinates = "lon lat height")
> (2) the rotated_pole is a variable without a dimension, because it is a
> variable without any data. How can I improve it here?
> (3) what is the meaning of ncl3 and ncl5? how to remove them from the
> metadata?
>
> Thanks so much in advance.
>
> Cheers,
> Mark
>
>
> ===metadata below=========
> ncdump -h
> tas_AFR-44_NCC-NorESM1-M_historical_r1i1p1_BCCR-WRF331C_v1_mon_195001-195012.nc
>
>
> netcdf
> tas_AFR-44_NCC-NorESM1-M_historical_r1i1p1_BCCR-WRF331C_v1_mon_195001-195012
> {
> dimensions:
>     time = UNLIMITED ; // (12 currently)
>     rlon = 213 ;
>     rlat = 220 ;
>     ncl3 = 9 ;
>     bnds = 2 ;
>     ncl5 = 1 ;
> variables:
>     double time(time) ;
>         time:long_name = "time" ;
>         time:standard_name = "time" ;
>         time:units = "days since 1949-12-01 00:00:00" ;
>         time:calendar = "standard" ;
>         time:axis = "T" ;
>         time:bounds = "time_bnds" ;
>     double rlon(rlon) ;
>         rlon:long_name = "longitude in rotated pole grid" ;
>         rlon:standard_name = "grid_longitude" ;
>         rlon:units = "degrees" ;
>         rlon:axis = "X" ;
>     double rlat(rlat) ;
>         rlat:long_name = "latitude in rotated pole grid" ;
>         rlat:standard_name = "grid_latitude" ;
>         rlat:units = "degrees" ;
>         rlat:axis = "Y" ;
>     char rotated_pole(ncl3) ;
>         rotated_pole:grid_mapping_name = "rotated_latitude_longitude" ;
>         rotated_pole:grid_north_pole_latitude = 90.f ;
>         rotated_pole:grid_north_pole_longitude = -180.f ;
>     float tas(time, rlat, rlon) ;
>         tas:long_name = "Near-Surface Air Temperature" ;
>         tas:standard_name = "air_temperature" ;
>         tas:units = "K" ;
>         tas:cell_methods = "time: mean" ;
>         tas:_FillValue = 1.e+20f ;
>         tas:missing_value = 1.e+20f ;
>         tas:coordinates = "lon lat" ;
>     double time_bnds(time, bnds) ;
>         time_bnds:long_name = "Time Bounds" ;
>         time_bnds:standard_name = "time bounds" ;
>         time_bnds:coordinates = "time bnds" ;
>     double height(ncl5) ;
>         height:long_name = "height" ;
>         height:standard_name = "height" ;
>         height:units = "m" ;
>         height:positive = "up" ;
>         height:axis = "Z" ;
>     double lon(rlat, rlon) ;
>         lon:long_name = "longitude" ;
>         lon:standard_name = "longitude" ;
>         lon:units = "degrees_east" ;
>         lon:bounds = "lon_bnds" ;
>         lon:coordinates = "lon lat" ;
>     double lat(rlat, rlon) ;
>         lat:long_name = "latitude" ;
>         lat:standard_name = "latitude" ;
>         lat:units = "degrees_north" ;
>         lat:bounds = "lat_bnds" ;
>         lat:coordinates = "lon lat" ;
>     double lon_bnds(rlat, rlon, bnds) ;
>         lon_bnds:long_name = "Longitude Bounds" ;
>         lon_bnds:standard_name = "longitude bounds" ;
>         lon_bnds:coordinates = "lon lat bnds" ;
>     double lat_bnds(rlat, rlon, bnds) ;
>         lat_bnds:long_name = "Latitude Bounds" ;
>         lat_bnds:standard_name = "latitude bounds" ;
>         lat_bnds:coordinates = "lon lat bnds" ;
>
>
>
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