This dataset provides daily and monthly Regional Climate Model (RCM) data on single levels from a number of experiments, models and time periods computed in the framework of the Coordinated Regional Climate Downscaling Experiment (CORDEX). The term "single levels" is used to express that the variables are computed at one vertical level which can be surface (or a level close to the surface) or a dedicated pressure level in the atmosphere. Multiple vertical levels are excluded from this catalogue entry.

High-resolution RCMs can provide climate projection information on regional and local scales in relatively fine detail, which cannot be obtained from lower resolution Global Climate Models (GCMs). This is manifested in more realistic descriptions of small-scale regional climate characteristics including extreme events. Consequently, outputs of such RCMs are important in supporting regional and local climate impact studies and adaptation decisions. RCMs are not independent from the GCMs, since the GCMs provide lateral and lower boundary conditions to the regional models.

The CORDEX experiments consist of RCM simulations representing different future socio-economic scenarios (forcings), different combinations of GCMs and RCMs and different ensemble members of the same GCM-RCM combinations. This experiment design through the ensemble members allows for studies addressing questions related to the key uncertainties in future climate change. These uncertainties come from differences in the scenarios of future socio-economic development, the imperfection of regional and global models used and the internal (natural) variability of the climate system.

The term "experiment" in the CDS form distinguishes between three main simulation categories:

• Evaluation: CORDEX experiment driven by ECMWF ERA-Interim reanalysis for a past period. These experiments can be used to evaluate the quality of the RCMs using perfect boundary conditions as provided by a reanalysis system. The period covered is typically 1980-2010;
• Historical: CORDEX experiment driven by boundary conditions provided by GCMs. These experiments cover a period for which modern climate observations exist. These experiments show how the RCMs perform for the past climate when forced by GCMs and can be used as a reference period for comparison with scenario runs for the future. The period covered is typically 1950-2005.;
• Scenario (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. The period covered is typically 2006-2100.

In CORDEX, the same experiments were run using different RCMs. Each RCM uses a variety of GCMs as lateral boundary conditions. The GCMs used are from the CMIP5 (5th phase of the Coupled Model Intercomparison Project) archive. Note that CMIP5 GCM datasets are also available in the CDS.

Additionally, the uncertainty related to internal variability of the climate system is sampled by running several simulations with the same RCM-GCM combination. On the forms, these are indexed as separate ensemble members (the naming convention for ensemble members is available in the documentation).

The data are produced by the participating institutes of the EURO-CORDEX project (see more details at the documentation section).

More details about the product are given in the Documentation section.