无法使用 NCO 连接全局层 netCDF 数据

Question

I am using monthly global potential evapotranspiration data from TerraClimate from 1958-2020 (available as 1 nc per year) and planning to concatenate all into single nc file. The data has a variable pet and three dimension ppt(time,lat,lon) .

I managed to combine all of the data using cod mergetime TerraClimate_*.nc and generate around 100GB of output file.

For analysis purpose in Windows machine, I need single netCDF file with order lat,lon,time . What I have done is as follows:

1. Reorder the dimension from time,lat,lon into lat,lon,time using ncpdq command

for fl in *.nc; do ncpdq -a lat,lon,time $fl ../pet2/$fl; done

2. Loop all file in the folder to make time the record dimension/variable used for concatenating files using ncks command

for fl in *.nc; do ncks -O --mk_rec_dmn time $fl $fl; done

3. Concatenates all nc files in the folder into one nc file using ncrcat command

ncrcat -h TerraClimate_*.nc -O TerraClimate_pet_1958_2020.nc

It's worked, but the result is not what I expected, it generate 458KB size of file, when I check the result using Panoply it provide wrong information, all have value -3276.7. See below picture.

I have check the files from step 1 and 2, and everything is correct.

I also try to concatenate only 2 files, using 1958 and 1959 data (each file 103MB), but the result still not what I expected.

ncrcat -h TerraClimate_pet_1958.nc TerraClimate_pet_1959.nc -O ../TerraClimate_pet_1958_1959.nc

Did I missed something on the code or write the wrong code? Any suggestion how to solve the problem?

UPDATE:

Here's the metadata of original data downloaded from above link.

Answer 1

Your commands appear to be correct, however I suspect that the data in the input files is packed. As explained in the ncrcat documentation here , the input data should be unpacked (eg, with ncpdq --unpack ) prior to concatenating all the input files (unless they all share the same values of scale_factor and add_offset ). If that does not solve the problem, then (1) there is likely an issue with _FillValue and (2) please post the pet metadata from a sample input file.