CDO CMOR Operator with CDO version > 1.8.1¶
cdo cmor demands a separate description because of its many options to rearrange model output and to add metadata.
It includes an interface to the Climate Model Output Rewriter library CMOR developed at PCMDI. This library
comprises a set of functions which can be used to produce NetCDF files that fulfill the requirements
of model intercomparison projects (MIPs). The output resulting from CMOR is ”self-describing” and
facilitates analysis of results across models.
CMOR functions feature a specific processing and require much input. The objective of cdo cmor is to
provide an easy interface to CMOR in order to automate and simplify its usage. cdo cmor can guarantee
the right CMOR configuration by calling the CMOR functions in correct order and with correctly inserted
CMOR labels and input attributes. A reduction of input can be achieved by exploiting the climate data
interface CDI. cdo cmor has a minimum requirement of one parameter and an input file.
Different versions of the CMOR library have been published over the years. A stable cdo operator was
developed at the DKRZ and Max-Planck-Institute for Meteorology based on CMOR version 2 which is
appropriate to build CMIP5 (phase 5 of the Coupled Model Intercomparison Project) compliant NetCDF
model output. The data standard of CMIP5 is fixed. Therefore, with the help of the CMIP5 database
generated at the DKRZ, the operator was validated.
As a next step, the operator has been prepared to include CMOR version 3 as well so that CMIP6 compliant
data can be produced. However, since changes of both, the CMIP6 data standard and request, as well as of
CMOR version 3 can not be excluded, the operator may require updates in order that the output complies
to the most recent CMIP6 standard.
The operator will be further enhanced at the DKRZ. Next updates will also focus on the long term goal
of facilitating the preparation of project compliant output for all CMIP phases and other projects.
Users have to be able to comprehend the MIP-table formulation of the desired project data standard, to
link their model variable to the correct CMOR variable and to specify
all required attributes, e.g. experiment id, for using cdo cmor. CMIP6 data standard is based on the
document CMIP6 Global Attributes, DRS, Filenames, Directory Structure, and CVs.
The scope of the configuration is too large for this wiki. The interested user is referred to the attached manual (cdo_cmor.pdf).
A tutorial session from 10.10.2017 is provided. The commands can be run on mistral.