ERA5

ERA5 is the fifth generation ECMWF atmospheric reanalysis of the global climate covering the period from January 1950 to present. ERA5 is produced by the Copernicus Climate Change Service (C3S) at ECMWF.

Reanalysis uses modelling so that geographic areas with no directly available climate observations can be filled in to generate ‘maps without gaps’ – complete and consistent representations of climate and atmospheric composition across time.

ERA5 provides hourly estimates of a large number of atmospheric, land and oceanic climate variables. The data cover the Earth on a 30km grid and resolve the atmosphere using 137 levels from the surface up to a height of 80km.

The ERA5 data is available at

• Single levels
• Pressure levels

The data set covers the period from 1979 to present. It will be soon available from 1950

ERA5 is produced using 4D-Var data assimilation and model forecasts in CY41R2 of the ECMWF Integrated Forecast System (IFS), with 137 hybrid sigma/pressure (model) levels in the vertical and the top level at 0.01 hPa. Atmospheric data are available on these levels and they are also interpolated to 37 pressure, 16 potential temperature and 1 potential vorticity level(s) by FULL-POS in the IFS.

The ERA5 dataset contains one (hourly, 31 km) high resolution realisation (referred to as “reanalysis” or “HRES”) and a reduced resolution ten member ensemble (referred to as “ensemble” or “EDA”). The ensemble is required for the data assimilation procedure, but as a by-product also provides an estimate of the relative, random uncertainty. Generally, the data are available at a sub-daily and monthly frequency and consist of analyses and short (18 hour) forecasts, initialised twice daily from analyses at 06 and 18 UTC. Most analysed parameters are also available from the forecasts. However, there are a number of forecast parameters, e.g. mean rates/fluxes and accumulations, that are not available from the analyses.

Requesting the data

When requesting the data provide the following information to get a quote:

• Do you require single levels, pressure levels or both
• Provide start year
• Provide end year
• Time
• Geographical areas

Variable mapping

Temperature is often the first variable that comes to mind when we talk about climate. However, it is insufficient to fully characterize the climate, and scientists have agreed on a number of variables to systematically observe Earth’s changing climate.

Single levels variables

Full list of single level variables available here.

Pressure levels variables

Full list of pressure level variables available here.

SAMPLE QUERY – SINGLE LEVELS

Usage1

Find Cloud base height of Newyork:

This parameter is calculated by searching from the second lowest model level upwards, to the height of the level where cloud fraction becomes greater than 1% and condensate content greater than 1.E-6 kg kg-1. Fog (i.e., cloud in the lowest model layer) is not considered when defining cloud base height

Lookup

Usage2

Find Ice temperature layer 1, 2, 3 AND 4 of Newyork:

This parameter is the sea-ice temperature in layer 1 (0 to 7cm).

The ECMWF Integrated Forecasting System (IFS) has a four-layer sea-ice slab:

Layer 1: 0-7cm

Layer 2: 7-28cm

Layer 3: 28-100cm

Layer 4: 100-150cm

The temperature of the sea-ice in each layer changes as heat is transferred between the sea-ice layers and the atmosphere above and ocean below.

Lookup

SAMPLE QUERY – PRESSURE LEVELS

Usage

Find out Specific cloud liquid water content for Newyork

This parameter is the mass of cloud liquid water droplets per kilogram of the total mass of moist air. The ‘total mass of moist air’ is the sum of the dry air, water vapour, cloud liquid, cloud ice, rain and falling snow. This parameter represents the average value for a grid box.

Lookup