Overwriting specific cells in netcdf

Question

Is there a netcdf operator (from nco or any python netcdf library) which can be used to overwrite specific cells in a netcdf file?

I want to change the values of a small region in a netcdf file containing global climate data. thanks!

Answer 1

This is easy with netCDF4-python. For example, suppose nc is your netCDF file, the variable is named var, and the index of the cell you want to change is (0,0,0). Then:

from netCDF4 import Dataset
new_value = -999
nc.variables['var'][0,0,0] = new_value

netCDF4 represents all netCDF arrays using numpy, which enables their powerful manipulation using numpy's slicing and other capabilities.

Answer 2

Or NCO's ncap2 does this in one command with

ncap2 -s 'var[0,0,0]=-999' in.nc out.nc

ncap2 is described here

Answer 3

CDO can set a specific lon-lat "rectangular" region to a value, here is the manual example:

To set all values in the region with the longitudes from 120E to 90W and latitudes from 20N to 20S to the constant value -999 use:

cdo setclonlatbox,-999,120,-90,20,-20 infile outfile