Introduction

At the beginning, CMIP6 data request management and XIOS I/O server

One of the big challenges in CMIP6 was to produce the ensemble of diagnostics requested by the CMIP6 Data Request (DR). Configuring the model outputs so that they comply with the Data Request is nearly unachievable by hand, given thousands of variables, hundreds of experiments to handle for groups participating to numbers of MIPs. Those models that use XIOS to handle their I/O can benefit from dr2xml to help writing XIOS configuration XML files so that output data files meet the CMIP6/CMOR format and metadata requirements. Dr2xml exploits the CMIP6 Data Request API to automate the generation of XIOS XML configuration files. To meet the CMIP6/CMOR data requirements, dr2xml relies on essential XIOS functionalities:

  • flexibility in the file naming and structure (multi or mono-variable files, mono-variable format being the CMIP standard)

  • flexibility in the time splitting length (useful to generate manageable file size)

  • possibility to glue any global attributes to the file (useful to include the set of mandatory CMOR global attributes)

  • ability to perform “on the fly” temporal and spatial operations, used to conform to CMIP6 “cell_methods” and “spatial_shapes”

Dr2xml fully exploits the Data Request content and scoping tools offered by the Data Request Python API (https://earthsystemcog.org/projects/wip/CMIP6DataRequest). Given some settings provided by the user, e.g. defining the MIP(s) the lab is involved in, the current experiment/simulation to be run, maximum priority for the outputs (see section 2 for the complete list of settings) dr2xml automatically:

  • identifies the list of requested CMOR variables that applies;

  • collects CMIP6 metadata associated to experiment(s) and CMOR variables (e.g.: experiment_id, variable_id, standard_name, long_name);

  • gets temporal shape (e.g.: ‘time mean over sea ice’) and spatial shape (e.g.: ‘global field 7 pressure levels’; ‘ocean basin meridional section’) of each required CMOR variable.

Now, dealing with new needs

This tool has been adopted by several users to make simulations outside of the CMIP6 scope. The current steps aim at generalizing the tool to other projects (e.g. CORDEX) and other data request (e.g. None or C3S one).

Several bugs are also corrected when they appear and new features are added to target users’ needs.