CMIP6 > Ensembles > Simulations

A simulation is an integration of a model carried out for an experiment, which in turn is part of a MIP.  All simulations belong to an ensemble of simulations, even if there is only one ensemble member. Due to the large number of ensembles and simulations that will be created for CMIP6,  ensemble and  simulation descriptions will be almost entirely auto-generated from the CMIP6 datasets submitted to the ESGF archives, meaning that there will be very little effort required from the modelling groups.

When valid CMIP6 datasets are submitted to an ESGF archive, their netCDF metadata are read on the ESGF node to determine which ensembles and simulations the datasets were created for. This is done automatically as part of the ESGF publication process.  The raw descriptions of these ensembles and simulations are then automatically sent to ES-DOC for publication.

Each CMIP6 netCDF file contains an attribute called “further_info_URL” which is the URL of a landing page from which all of the relevant documentation relevant to the data may be accessed. This landing page will describe the ensemble for which the simulation was run and will contain links to documentation for the ensemble’s experiment,  the simulation itself and any other simulations that the ensemble may contain. Each Simulation document will contain a link to the description of the model that ran it. More details on the this landing page may be found here.

A small amount  of manual input will be required to describe how the simulations vary across the four “ensemble axes”, i.e. the realization (r), initialization (i), perturbation (p) and forcing (f) axes of the ensemble. If the ensemble does not vary along one of these axes then no action is necessary. This extra information will be collected either via spreadsheet or in an iPython notebook.

The workflow is illustrated here, demonstrating that after sending datasets to the ESGF archive, no further action is required from a modelling institute until after the further_info_URL has been automatically created, when the ensemble axis information (if any) needs to be added:

Extra effort will also be required to detail how each ensemble of simulations conformed to the experiment’s requirements, which is covered here.