Ploting a concatenated netCDF does not give desired plot

Question

I concatenaded 31 netcdf files using ncrcat.I then oppend the output file in jupyter notebook and tried to create a plot in respect with time,but I get the following ,any fixes?

Answer 1

It appears your time coordinate values are all identical. Be sure you are using a recent version of ncrcat and that NCO was built with UDUnits enabled. Otherwise the time concatenation, aka rebasing, of your files cannot be expected to work correctly.

zender@sastrugi:~$ ncrcat -r
NCO netCDF Operators version 4.9.6-alpha03 "Osiris Rex" built by zender on sastrugi at Oct 26 2020 12:50:42
ncrcat version 4.9.6-alpha03
Linked to netCDF library version 4.7.4 compiled Oct  5 2020 21:03:41
Copyright (C) 1995--2020 Charlie Zender
This program is part of NCO, the netCDF Operators.
NCO is free software and comes with a BIG FAT KISS and ABSOLUTELY NO WARRANTY
You may redistribute and/or modify NCO under the terms of the
3-Clause BSD License with exceptions described in the LICENSE file
BSD: https://opensource.org/licenses/BSD-3-Clause
LICENSE: https://github.com/nco/nco/tree/master/LICENSE
Homepage: http://nco.sf.net
Code: http://github.com/nco/nco
Build-engine: Autoconf
User Guide: http://nco.sf.net/nco.html
Configuration Option:   Active? Meaning or Reference:
Check _FillValue    Yes http://nco.sf.net/nco.html#mss_val
DAP support     Yes http://nco.sf.net/nco.html#dap
Debugging: Custom   No  Pedantic, bounds checking (slowest execution)
Debugging: Symbols  No  Produce symbols for debuggers (e.g., dbx, gdb)
GNU Scientific Library  Yes http://nco.sf.net/nco.html#gsl
HDF4 support        No  http://nco.sf.net/nco.html#hdf4
Internationalization    No  http://nco.sf.net/nco.html#i18n (pre-alpha)
Logging         No  http://nco.sf.net/nco.html#dbg
netCDF3 64-bit offset   Yes http://nco.sf.net/nco.html#lfs
netCDF3 64-bit data Yes http://nco.sf.net/nco.html#cdf5
netCDF4/HDF5 support    Yes http://nco.sf.net/nco.html#nco4
OpenMP SMP threading    Yes http://nco.sf.net/nco.html#omp
Regular Expressions Yes http://nco.sf.net/nco.html#rx
**UDUnits2 conversions  Yes http://nco.sf.net/nco.html#udunits**

Answer 2

You might also try doing the merge with

cdo mergetime infiles*.nc merged_file.nc 

Check the output dates from the command line with

cdo showdate merged_file.nc