Extension 1 - CORDEX Overview

This catalogue entry provides Regional Climate Model (RCM) data on single levels from a number of experiments, models, domains, resolutions, ensemble members, time frequencies and periods computed over several regional domains all over the World in the framework of the Coordinated Regional Climate Downscaling Experiment (CORDEX). The term "single levels" is used to express that the variables are 2D-matrices computed on 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 Regional Climate Models (RCMs) can provide climate change information on regional and local scales in relatively fine detail, which cannot be obtained from coarse scale Global Climate Models (GCMs). This is manifested in better description of small-scale regional climate characteristics and also in more accurate representation of extreme events. Consequently, outputs of such RCMs are indispensable 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. In that sense RCMs can be viewed as magnifying glasses of the GCMs.

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. This experiment design allows for studies addressing questions related to the key uncertainties in future climate change:

• what will future climate forcing be?
• what will be the response of the climate system to changes in forcing?
• what is the uncertainty related to natural variability of the climate system?

The term "region" in the CDS form refers to the different regional domains, which are as follows:

• EUR: European domain from 27°N to 72°N and from 22°W to 45°E. The horizontal resolution for this domain is 0.11° x 0.11° (EUR-11).
• NAM: North-American domain from 12°N to 59°N and from 171°W to 24°W. The horizontal resolutions for this domain are 0.22° x 0.22° (NAM-22) and 0.44° x 0.44° (NAM-44).

Additional details on each CORDEX geographical domain are available at https://cordex.org/domains/.

The term "experiment" in the CDS form refers to three main 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 which covers a period for which modern climate observations exist. Boundary conditions are provided by GCMs. These experiments, that follow the observed changes in climate forcing, 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: Ensemble of CORDEX climate projection experiments using RCP (Representative Concentration Pathways) forcing scenarios. These scenarios are the RCP 2.6, 4.5 and 8.5 scenarios providing different pathways of the future climate forcing. Boundary conditions are provided by GCMs. The period covered is typically 2006-2100.

In CORDEX, the same experiments were done using different RCMs (labelled as “Regional Climate Model” in the CDS form).

In addition, for each RCM, there is a variety of GCMs, which can be used as lateral boundary conditions. The GCMs used are coming from the CMIP5 (5th phase of the Coupled Model Intercomparison Project) archive. These GCM boundary conditions are labelled as “Global Climate Model” in the form and 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). For each GCM, the same experiment was repeatedly done using slightly different conditions (like initial conditions or different physical parameterisations for instance) producing in that way an ensemble of experiments closely related. More details behind these sequential ensemble numbers is available in the detailed documentation.

All known issues about the CORDEX data are documented through the ES-DOC Errata Service : https://errata.es-doc.org/.

The data are produced by the institutes and modelling centres participating in the different CORDEX domains with partial support from different international and national contributions (including support from COPERNICUS for some of the EURO-CORDEX runs and for helping in the data curation and ESGF archiving process in some domains). 

Recommended search procedure: 

1. Select the CORDEX region of interest
2. Select the spatial resolution of interest
3. Select the CORDEX experiment (e.g., future scenario) of interest
4. Select the required variable(s) for your analysis.
5. Select the required time period (which depends on the experiment).
6. The search interface will adapt the other selection fields according to the available data (e.g., which models provides the variable you aim for, how many ensemble are available, etc.)

MARKDOWN FORMAT for the overview text

This catalogue entry provides Regional Climate Model (RCM) data on single levels from a number of experiments, models, domains, resolutions, ensemble members, time frequencies and periods computed over several regional domains all over the World in the framework of the Coordinated Regional Climate Downscaling Experiment (CORDEX). The term "single levels" is used to express that the variables are 2D-matrices computed on 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 Regional Climate Models (RCMs) can provide climate change information on regional and local scales in relatively fine detail, which cannot be obtained from coarse scale Global Climate Models (GCMs). This is manifested in better description of small-scale regional climate characteristics and also in more accurate representation of extreme events. Consequently, outputs of such RCMs are indispensable 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. In that sense RCMs can be viewed as magnifying glasses of the GCMs.

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. This experiment design allows for studies addressing questions related to the key uncertainties in future climate change:

- what will future climate forcing be?
- what will be the response of the climate system to changes in forcing?
- what is the uncertainty related to natural variability of the climate system?

The term "region" in the CDS form refers to the different domains, which are as follows:

-**EUR**: European domain from 27°N to 72°N and from 22°W to 45°E. The horizontal resolution for this domain is 0.11° x 0.11° (EUR-11).

-**NAM**: North-American domain from 12°N to 59°N and from 171°W to 24°W. The horizontal resolutions for this domain are 0.22° x 0.22° (NAM-22) and 0.44° x 0.44° (NAM-44).

Additional details on each CORDEX geographical domain are available at https://cordex.org/domains/.

The term "experiment" in the CDS form refers to three main 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 which covers a period for which modern climate observations exist. Boundary conditions are provided by GCMs. These experiments, that follow the observed changes in climate forcing, 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**: Ensemble of CORDEX climate projection experiments using RCP (Representative Concentration Pathways) forcing scenarios. These scenarios are the RCP 2.6, 4.5 and 8.5 scenarios providing different pathways of the future climate forcing. Boundary conditions are provided by GCMs. The period covered is typically 2006-2100.

In CORDEX, the same experiments were done using different RCMs (labelled as “Regional Climate Model” in the CDS form).

In addition, for each RCM, there is a variety of GCMs, which can be used as lateral boundary conditions. The GCMs used are coming from the CMIP5 (5th phase of the Coupled Model Intercomparison Project) archive. These GCM boundary conditions are labelled as “Global Climate Model” in the form and 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). For each GCM, the same experiment was repeatedly done using slightly different conditions (like initial conditions or different physical parameterisations for instance) producing in that way an ensemble of experiments closely related. More details behind these sequential ensemble numbers is available in the detailed documentation.

All known issues about the CORDEX data are documented through the ES-DOC Errata Service : https://errata.es-doc.org/.

The data are produced by the institutes and modelling centres participating in the different CORDEX domains with partial support from different international and national contributions (including support from COPERNICUS for some of the EURO-CORDEX runs and for helping in the data curation and ESGF archiving process in some domains). 

Recommended search procedure: 

1. Select the CORDEX region of interest
2. Select the spatial resolution of interest
3. Select the CORDEX experiment (e.g., future scenario) of interest
4. Select the required variable(s) for your analysis.
5. Select the required time period (which depends on the experiment).
6. The search interface will adapt the other selection fields according to the available data (e.g., which models provides the variable you aim for, how many ensemble are available, etc.)

YAML FORMAT for the Description table

---
Data-Description:

Data-type: Gridded

Horizontal-coverage: Depends on the regional domain (grid projection may differ among RCMs)

Horizontal-resolution: 0.11° x 0.11°, 0.22° x 0.22° or 0.44° x 0.44° depending on the region.

Vertical-resolution: Variables are provided in one single level (which may differ among variables)

Temporal-coverage:

-'evaluation runs are from 1989 to 2008'

-'historical runs are from 1951 to 2005'

-'scenario runs are from 2006 to 2100'

Temporal-resolution: 3h, 6h, daily, monthly and seasonal

File-format: NetCDF4

Conventions: Climate and Forecast (CF) Metadata Convention v1.6

Versions: Latest version of the data is provided.

Update-frequency: Regular quarterly updates

YAML FORMAT for the variables

VARIABLES:

    Name: '2m temperature'

    Short-name: 'tas'

    Units: 'K'

    Description: 'The temperature of the air near the surface (or ambient temperature). The data represents the mean over the aggregation period at 2m above the surface.'

    Name: '200 hPa temperature'

    Short-name: 'ta200'

    Units: 'K'

    Description: 'The temperature of the air at 200hPa. The data represents the mean over the aggregation period at 200hPa pressure level.'

    Name: 'Minimum 2m temperature in the last 24 hours'

    Short-name: 'tasmin'

    Units: 'K'

    Description: 'The minimum temperature of the air near the surface. The data represents the daily minimum at 2m above the surface.'

    Name: 'Maximum 2m temperature in the last 24 hours'

    Short-name: 'tasmax'

    Units: 'K'

    Description: 'The maximum temperature of the air near the surface. The data represents the daily maximum at 2m above the surface.'

    Name: 'Mean precipitation flux'

    Short-name: 'pr'

    Units: 'kg.m^-2.s^-1'

    Description: 'The minimum temperature of the air near the surface. The data represents the daily minimum at 2m above the surface.'

    Name: 'Mean evaporation flux'

    Short-name: 'evspsbl'

    Units: 'kg.m^-2.s^-1'

    Description: 'The mass of surface and sub-surface liquid water per unit area ant time, which evaporates from land. The data includes conversion to vapour phase from both the liquid and solid phase, i.e., includes sublimation, and represents the mean over the aggregation period.'

    Name: '2m surface relative humidity'

    Short-name: 'hurs'

    Units: '%'

    Description: 'The relative humidity is the percentage ratio of the water vapour mass to the water vapour mass at the saturation point given the temperature at that location. The data represents the mean over the aggregation period at 2m above the surface.'

   Name: '2m surface specific humidity'

    Short-name: 'huss'

    Units: 'Dimensionless'

    Description: 'The amount of moisture in the air at 2m above the surface divided by the amount of air plus moisture at that location. The data represents the mean over the aggregation period at 2m above the surface.'

    Name: 'Surface pressure'

    Short-name: 'ps'

    Units: 'Pa'

    Description: 'The air pressure at the lower boundary of the atmosphere. The data represents the mean over the aggregation period.'

    Name: 'Mean sea level pressure'

    Short-name: 'psl'

    Units: 'Pa'

    Description: 'The air pressure at sea level. In regions where the Earth's surface is above sea level the surface pressure is used to compute the air pressure that would exist at sea level directly below given a constant air temperature from the surface to the sea level point. The data represents the mean over the aggregation period.'

   Name: '10m Wind Speed'

    Short-name: 'sfcWind'

    Units: 'm.s^-1'

    Description: 'The magnitude of the two-dimensional horizontal air velocity. The data represents the mean over the aggregation period at 10m above the surface.'

    Name: 'Surface solar radiation downwards'

    Short-name: 'rsds'

    Units: 'W.m^-2'

    Description: 'The downward shortwave radiative flux of energy per unit area. The data represents the mean over the aggregation period at the surface.'

    Name: 'Surface thermal radiation downwards'

    Short-name: 'rlds'

    Units: 'W.m^-2'

    Description: 'The downward longwave radiative flux of energy inciding on the surface from the above per unit area. The data represents the mean over the aggregation period.'

    Name: 'Surface upwelling shortwave radiation'

    Short-name: 'rsus'

    Units: 'W.m^-2'

    Description: 'The upward shortwave radiative flux of energy from the surface per unit area. The data represents the mean over the aggregation period at the surface.'

    Name: 'Total cloud cover'

    Short-name: 'clt'

    Units: 'Dimensionless'

    Description: 'Total refers to the whole atmosphere column, as seen from the surface or the top of the atmosphere. Cloud cover refers to fraction of horizontal area occupied by clouds. The data represents the mean over the aggregation period.'

    Name: '500 hPa geopotential'

    Short-name: 'zg500'

    Units: 'm'

    Description: 'The gravitational potential energy per unit mass normalized by the standard gravity at 500hPa at the same latitude. The data represents the mean over the aggregation period at 500hPa pressure level.'

    Name: '10m u-component of wind'

    Short-name: 'uas'

    Units: 'm.s^-1^'

    Description: 'The magnitude of the eastward component of the wind. The data represents the mean over the aggregation period at 10m above the surface.'

    Name: '10m v-component of wind'

    Short-name: 'vas'

    Units: 'm.s^-1^'

    Description: 'The magnitude of the northward component of the wind. The data represents the mean over the aggregation period at 10m above the surface.'

    Name: '200 hPa u-component of the wind'

    Short-name: 'ua200'

    Units: 'm.s^-1^'

    Description: 'The magnitude of the eastward component of the wind. The data represents the mean over the aggregation period at 200hPa above the surface.'

     Name: '200 hPa v-component of the wind'

    Short-name: 'va200'

    Units: 'm.s^-1

    Description: 'The magnitude of the northward component of the wind. The data represents the mean over the aggregation period at 200hPa above the surface.'

   Name: '850 hPa u-component of the wind'

    Short-name: 'ua850'

    Units: 'm.s^-1^'

    Description: 'The magnitude of the eastward component of the wind. The data represents the mean over the aggregation period at 850 hPa above the surface.'

     Name: '850 hPa v-component of the wind'

    Short-name: 'va850'

    Units: 'm.s^-1^'

    Description: 'The magnitude of the northward component of the wind. The data represents the mean over the aggregation period at 850 hPa above the surface.'

   Name: 'Total run-off flux'

    Short-name: 'mrro'

    Units: 'kg.m^-2.s^-1'

    Description: 'The mass of surface and sub-surface liquid water per unit area and time, which drains from land. The data represents the mean over the aggregation period.'

    Name: 'Land area fraction'

    Short-name: 'sftif'

    Units: '%'

    Description: 'The fraction (in percentage) of grid cell occupied by land surface. The data is time-independent.'

   Name: 'Orography'

    Short-name: 'orog'

    Units: 'm'

    Description: 'The height above the geoid (being 0.0 over the ocean). The data is time-independent.'