Recipe: Read file metadata

Problem

We want to read metadata of downloaded file.

Solution

For the purpose of this example, we assume that we have already downloaded the file c1440_NR.inst01hr_3d_T_Cv.20060918_0900z.nc4 from the ftp server. For more information about file naming conventions, and how to download a file from the ftp server, please follow the links in the #See Also section.

The easiest way to read metadata of a G5NR data file is to use the utility ncdump that comes with the NetCDF-4 installation.

For header information only (no data), one can issue the command

> ncdump -h c1440_NR.inst01hr_3d_T_Cv.20060918_0900z.nc4

resulting in

netcdf c1440_NR.inst01hr_3d_T_Cv.20060918_0900z {
dimensions:
	lon = 720 ;
	lat = 361 ;
	lev = 72 ;
	time = UNLIMITED ; // (1 currently)
variables:
	double lon(lon) ;
		lon:long_name = "longitude" ;
		lon:units = "degrees_east" ;
	double lat(lat) ;
		lat:long_name = "latitude" ;
		lat:units = "degrees_north" ;
	double lev(lev) ;
		lev:long_name = "vertical level" ;
		lev:units = "layer" ;
		lev:positive = "down" ;
		lev:coordinate = "eta" ;
		lev:standard_name = "model_layers" ;
	int time(time) ;
		time:long_name = "time" ;
		time:units = "minutes since 2006-09-18 09:00:00" ;
		time:time_increment = 10000 ;
		time:begin_date = 20060918 ;
		time:begin_time = 90000 ;
	float T(time, lev, lat, lon) ;
		T:long_name = "air_temperature" ;
		T:units = "K" ;
		T:_FillValue = 1.e+15f ;
		T:missing_value = 1.e+15f ;
		T:fmissing_value = 1.e+15f ;
		T:scale_factor = 1.f ;
		T:add_offset = 0.f ;
		T:standard_name = "air_temperature" ;
		T:vmin = -1.e+15f ;
		T:vmax = 1.e+15f ;
		T:valid_range = -1.e+15f, 1.e+15f ;

// global attributes:
		:History = "File written by MAPL_CFIO" ;
		:Source = "wmp-Ganymed-4_0_BETA8" ;
		:Title = "3d,1-Hourly,Instantaneous,Model-Level,Coarsened to 1/2 degree,Air Temperature" ;
		:Contact = "http://gmao.gsfc.nasa.gov" ;
		:Conventions = "COARDS" ;
		:Institution = "NASA Global Modeling and Assimilation Office" ;
		:References = "http://gmao.gsfc.nasa.gov" ;
		:Comment = "7-km_Non-Hydrostatic_Nature_Run" ;
}

See Also

1. Recipe: File naming conventions
2. Recipe: Retrieve (global) data from FTP server