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The regional climate projections in the Climate Data Store (CDS) are a quality-controlled subset of the wider CORDEX data over Europe. These data represent only a small subset of CORDEX archive. A set of 30 core variables from the CORDEX archive were identified for the CDS. These are the most used of the CORDEX data. These variables are provided from 4 of the most popular CORDEX experiments 5 CORDEX experiment types (evaluation, historical and 3 RCP scenarios) that are derived (downscaled) from the CMIP5 experiments. WHAT IS EXACTLY MEANT HERE??
The CDS subset of CORDEX data have been through a metadata quality control procedure which ensures a high standard of reliability of the data. It may be for example that similar data can be found in the main CORDEX archive however these data come with no quality assurance and may have metadata errors or omissions. The quality-control process means that the CDS subset of CORDEX data is further reduced to exclude data that have metadata errors or inconsistencies. It is important to note that passing of the quality control should not be confused with validity: for example, it will be possible for a file to have fully compliant metadata but contain gross errors in the data that have not been noted. In other words, it means that the quality control is purely technical and does not contain any scientific evaluation (for instance consistency check).
In addition, CORDEX data for CDS includes Persistent IDentifiers (PID) in their metadata which allows CDS users to report any error during the scientific analysis. The error will be at least documented on the ESGF Errata Service (http://errata.es-doc.org) but also corrected with a new dataset version TO BE CHECKED SINCE THE LATEST VERSION IS PUBLISHED NOW! published on the CDS.planned to be documented in the CDS. In this case the users will have the option to reproduce their results using the old, outdated datasets too.
Data Format
The CDS subset of CORDEX data are provided as NetCDF files. NetCDF (Network Common Data Form) is a file format that is freely available and commonly used in the climate modeling community.
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- scenario experiments RCP2.6, RCP4.5, RCP8.5: ensemble of CORDEX climate projection experiments driven by boundary conditions from GCMs using RCP (Representative Concentration Pathways) forcing scenarios. The scenarios used here are RCP 2.6, 4.5 and 8.5, they provide different pathways of the future climate forcing.
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GCM vs. RCM matrix
Regional climate Climate Model (RCM) simulations needs lateral boundary conditions related to the global CMIP experiment of interest. Those boundary conditions impose changing conditions for the whole regional climate run. The from Global Climate Models (GCMs). At the moment the CDS-CORDEX subset boundary conditions are extracted from CMIP5 global projections. A set of boundary conditions can be extracted from a given experiment of a given driving GCM. Thus, CORDEX framework requires each RCM downscale a minimum of 3 GCMs for 2 scenarios (at least RCP8.5 and RCP2.6). The two scenarios more or less cover the full IPCC range. The number of 3 for the GCMs is a minimum, ideally 5-6 GCMs would be better, if feasible. The C3S-CORDEX subset aims to fill the gaps in this matrix between GCMs (aka "driving models), RCMs and RCMsRCPs.
Regional Models
The models included in the CDS-CORDEX subset are detailed in the table below, these include 12 of the models from the main CORDEX archive. However a small number of models were not included as the data from the models have a research-only restriction on their use, but all data in the CDS are released without restriction.
The CDS-CORDEX subset also include a version number. This integer identifies the version of the RCM simulations/run and not the version of the RCM itself. All models runs start with "v1" but new runs can occur for many reasons or computing errors. Runs numbers different from “v1” means new simulations relative to the first “v1” one. It might not mean a new version.
Driving Global Models
The driving GCMs used to produced the CDS-CORDEX subset are details in the table below, these include 8 of the models from the main CMIP5 archive. However a small number of models were not included as the data from the models have a research-only restriction on their use, but all data in the CDS are released without restriction.
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