1 - Introduction
This article describes how users can access the family of ERA5 datasets via the Climate Data Store (CDS) infrastructure.
ERA5 data can be downloaded through the CDS either via the CDS web interface or programmatically using the CDS API service.
Any data in the CDS catalogue can be accessed in these two ways. And since such data is kept online, access is usually fast. Some parts of the ERA5 dataset are not listed in the CDS catalogue. These are only accessible through the CDS API service. An example is ERA5 model level data that resides in the ECMWF's MARS tape archive. The extraction of such data from tape can lead to significantly longer retrieval times than data that is available online.
Users are now able to check the status of the CDS queue. You will be able to view status of requests submitted by yourself (you need to log into the CDS) and other users: https://cds.climate.copernicus.eu/live/queue
2 - Prerequisites
- Learn more about the family of ERA5 datasets, and browse through the ERA5 data documentation and ERA5-Land data documentation.
- CDS account - If you do not yet have a CDS account, please create one HERE.
- Accept the Copernicus licence by creating a test download using the CDS Download web form interface (see below).
3 - Downloading online ERA5 family data through the CDS web interface
- Go to the C3S climate data store (CDS).
- Type 'ERA5' in the search box.
- Follow the ERA5 dataset title link of interest (there will be many more hits).
Currently there are eight online ERA5 and two ERA5-Land catalogue entriesShow ERA5 catalogue entries in the CDS
- ERA5 hourly data on single levels from 1979 to present
- ERA5 monthly averaged data on single levels from 1979 to present
- ERA5 hourly data on pressure levels from 1979 to present
- ERA5 monthly averaged data on pressure levels from 1979 to present
- ERA5-Land hourly data from 1981 to present
- ERA5-Land monthly averaged data from 1981 to present
- Each of these dataset catalogue entries includes the following tabs:
- Overview . This gives a description of the selected dataset and metadata information (e.g. spatial details, file format, variables, etc).
- Documentation . This provides links to detailed documentation about the dataset.
- Download data . This is a download web form.
- Go to the Download data tab to make your selection for ERA5 data retrieval. Using this web interface, you can:
- make selections as per your requirements. For your convenience only valid combinations will show; invalid combinations are greyed out interactively.
You will need to do this regardless whether you are accessing data through the web interface or through the CDS API (see below).
Click on the button Submit Form at the bottom right to submit your data request (you must be logged in and have accepted the terms and conditions before submitting your request).
- You will now be redirected to the Your requests page.
Once your request has been processed you can download the data by clicking the green Download button. You can check the Live status of your request .
4 - Download ERA5 family data through the CDS API
First: Install CDS API on your machine
- This is Python based.
- This may require some basic knowledge of Python. However, in most cases common-sense adaptions of example requests obtained from the web interface should be sufficient.
- Install the CDS API:
- You are recommended to use the latest release of package CDS API.
- Run CDS API requests, either interactively or in batch mode.
In a small number of cases, users may experience some issues when requesting data from the CDS API. The most common issues are documented here.
Option A: Download ERA5 family data stored on CDS disks - FAST ACCESS
Build a basic CDS API request.
You can use the CDS web interface to help you build your CDS API download script.
In the Download data tab, make some selections, then click the button Show API request at the bottom left and you will be presented with the script.
Copy and paste this to your preferred text editor.Basic CDS API script example (for ERA5 1979-present) to download temperature at a given pressure level, 1000 hPa is shown HERE.
- Refine your CDS API script for ERA5 data listed in CDS for optional post-processing.
- For a different grid resolution, use the key 'grid'.
- Please note that the ERA5 native grid of online CDS is 0.25°x0.25° (atmosphere), 0.5°x0.5° (ocean waves), mean, spread and members: 0.5°x0.5° (atmosphere), 1°x1° (ocean waves). ERA5-Land: 0.1°x0.1°. So this will be returned by default.
- Click here for a sample script (for ERA5 1979-present) that downloads temperature at a given pressure level at 1000 hPa for a geographical subset of the data and specified grid
To retrieve data efficiently using the CDS API please have a look at the efficiency tips section on CDS documentation.
Requests for ERA5 data in NetCDF
When requesting ERA5 data from the CDS in NetCDF (web or CDS API), users should not request ERA5 reanalysis atmospheric data, wave data, and ensemble data in one request. This is because the data has different spatial grids, which can cause issues for the current grib to NetCDF converter and produce incorrect results.
Option B: Download ERA5 family data that is NOT listed in the CDS online catalogue - SLOW ACCESS
Although some flavours of the ERA5 family data is not online in the CDS (i.e. not available through the interactive web download form), it is accessible through CDS API. This embraces ERA5-complete and ERA5.1-complete, which provide data in the 'raw' format as they were produced:
- native grid rather than regridded into regular lat-lon,
- model and potential temperature/vorticity levels, in addition to pressure levels and surface fields,
- full two-dimensional ocean-wave spectra in addition to integrated wave parameters,
- explicit distinction between analysis, short-forecast and other, more technical, products.
The ERA5-Land dataset at the native 9km octahedral grid is an exception and is currently not available via the CDS API protocol. However, all information is available online at the slightly reduced 0.1°x0.1° regular lat-lon grid (access via Option A, above).
Due to the vast volume of these datasets (currently about 6 petabyte) these are not stored on spinning disk, but reside in the ECMWF's MARS tape archive, instead. Access to this data is in general much slower. Please note that the ERA5 back extension (preliminary version) 'raw' format from MARS is not yet available (expected around the end of 2020).
Please be aware that there is an additional queueing system for downloading data from the ECMWF's MARS archive - expect several hours to several days for submitted requests to complete at this time. You can check the Live status of your request
You can discover the ERA5-complete structure and learn how to build a CDS API request by following these steps:
- Open the MARS ERA5 catalogue
browse for discovery, and browse your way to the parameter level to build a request.
- More information on the available streams, product types and levels is available in the ERA5 data documentation.
- On the parameter level, use the left-mouse button and the shift key to select more than one field in one retrieval.
To retrieve MARS data efficiently (and get your data quicker!) you should retrieve all the data you need from one tape, then from the next tape, and so on.
As a rule of thumb everything shown on one page at parameter level in the MARS ERA5 catalogue is grouped together on one tape
- For analysis fields this is one month of data with respect to one particular level type (e.g. surface).
- For forecast fields on model levels this is limited to one single day.
Use the " View MARS request " feature - this will help you build your own CDS API Python script to retrieve the data through the CDS API.Example: Download ERA5 model level analysis data (temperature) in the native spherical harmonics representation in GRIB format.
- Tailor your request to
- re-grid to the desired regular lat-lon resolution
- convert to NetCDF (works for regular grids only, i.e., so you need to use the 'grid' keyword as well)
select sub areasExample to download model level ERA5 analysis data (temperature) for a given area at a regular lat/lon grid in NetCDF format.
For ERA5.1-complete follow the same procedure as for era5-complete explained above, however:
edit the script to change:
data is only available for the years 2000-2006 inclusive - so make sure that your request dates are within this time period.
For ERA5-complete preliminary back-extension follow the same procedure as for era5-complete explained above, however:
edit the script to change:
data is available for the years 1950-1978 inclusive - so make sure that your request dates are within this time period.