NetCDF : set variable as constant in time

问题

I am dealing with netCDF files with the following structure :

netcdf YYY {
dimensions:
    Time = UNLIMITED ; // (XXX currently)
    lat = XX ;
    lon = XX ;
variables:
    double U_p_500hPa(Time, lat, lon) ;
        U_p_500hPa:units = "m/s" ;
        U_p_500hPa:_FillValue = -9999. ;
        U_p_500hPa:description = "U at 500hPa" ;
        U_p_500hPa:PlotLevelID = "500 hPa" ;
    float XLAT(Time, lat, lon) ;
        XLAT:FieldType = 104 ;
        XLAT:MemoryOrder = "XY " ;
        XLAT:description = "LATITUDE, SOUTH IS NEGATIVE" ;
        XLAT:units = "degree_north" ;
        XLAT:stagger = "" ;
    float XLONG(Time, lat, lon) ;
        XLONG:FieldType = 104 ;
        XLONG:MemoryOrder = "XY " ;
        XLONG:description = "LONGITUDE, WEST IS NEGATIVE" ;
        XLONG:units = "degree_east" ;
        XLONG:stagger = "" ;

The thing is XLONG and XLAT do not actually depend of time.

Therefore i wonder if there is a way to set the coordinates variables as independent of time in order to get lighter files ?

I was thinking about using nco but I couldn't find the way to do so.

Thanks in advance for any help !

回答1:

Read the manual to find the meaning of the following, an approach that subsets the time-dependent variable into one file, averages the Time dimension out of the coordinates, and then appends the time-constant coordinates back into the file with the time-varying variable.

ncks -v U_p_500hPa in.nc u.nc
ncwa -a Time -v XLAT,XLONG in.nc latlon.nc
ncks -A latlon.nc u.nc

来源：https://stackoverflow.com/questions/53428813/netcdf-set-variable-as-constant-in-time