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titleTable of Contents

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1 - Introduction

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This article describes how users can access ERA5 data access the family of ERA5 datasets via the Climate Data Store (CDS) infrastructure.

ERA5 data can be downloaded through the CDS either through via the CDS web interface or programmatically using the CDS API service.

Some ERA5 datasets do not appear in CDS, but they are accessible through CDS API, for example, ERA5 model level data archived at 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 only accessible through the CDS API service. An example is ERA5 model level data that resides in the ECMWF's MARS tape archive. This implies, in some situations, accessing data not available on disks but archived in the tape library (hence longer retrieval times).

Table of Contents

1 - Prerequisites

  • Read What is ERA5 and the ERA5 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).

2 - Downloading ERA5 data through the CDS web interface

The extraction of such data from tape can lead to significantly longer retrieval times than data that is available online.

Tip

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

3 - Downloading online ERA5 family data through the CDS web interface

  1. Go to the C3S climate data store (CDS).
  2. Type 
  3. Go to the C3S climate data store (CDS).
  4. On the top menu bar, click on 'Datasets'.
  5. On the left-hand side menu, expand 'Product type' and select Product type of interest (e.g. 'Reanalysis' for ERA5 datasets). Or you can search 'ERA5' in the search box.
  6. Follow the ERA5 dataset title link of interest to the full dataset record.

    The full dataset record includes:

    • Overview tab. This gives a description of the selected dataset and metadata information (e.g. spatial details, file format, variables, etc).
    • Documentation tab. This provides links to detailed documentation about the dataset.
    • Download data tab. This is a Download data web form. Using this web interface, you can:
      • make selections as per your requirements
      • submit your request online (you will need to login if not already logged in)  
        (warning) Tip: Upon submitting the download form, you will be prompted to accept the data licence (if you have not yet accepted it)! Please note that whether you are downloading the data through the web interface or through the CDS API, you must accept the data licence.
      • display the API script which corresponds to your selection, by clicking on the Show API request button.
    (there will be many more hits).

  7. Currently there are eight online ERA5 and two ERA5-Land catalogue entries  

    Expand
    titleShow ERA5 catalogue entries in the CDS


  8. 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.
  9. Go to the Download data tab to make your selection for ERA5 data retrieval.
  10. Click on button 'Submit Form' to submit  your data request. Provided you have accepted the Copernicus Licence, 'your requests' page will be displayed showing the status of your submitted request.

3 - Download ERA5 data through the CDS API

Step A: Install CDS API on your machine

  1. Python and pip: You are expected to have at least some basic understanding of Python and in particular know how to install packages on your local machine using pip.
  2. Install the CDS API:
    • on linux or on cygwin, please follow the instructions HERE.
    • Windows users may follow the instructions HERE instead.
  3. You are recommended to use the latest release of package CDS API (tested with version 0.1.1).

Step B: Download ERA5 data listed in CDS through CDS API

  1. 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.

    • accept the data licence in the Terms of use section (in case you had not yet accepted it). You will only see this section after you have logged in.

      Note

      You will need to do this regardless whether you are accessing data through the web interface or through the CDS API (see below).


  2. 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).

  3. 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

  1. 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.
  2. Install the CDS API:
    • this may require some basic knowledge of pip, in particular know how to install packages on your local machine using pip.
    • On linux or on cygwin, please follow the instructions HERE.
    • Windows users may follow the instructions HERE instead.
    • Mac users may follow the instructions HERE.
  3. You are recommended to use the latest release of package CDS API.
  4. Run CDS API requests, either interactively or in batch mode.
Note

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

  1. 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.

      Expand
      titleBasic CDS API script example (for ERA5 1940-present) to download temperature at a given pressure level, 1000 hPa is shown HERE.


      Code Block
      languagetext
      #!/usr/bin/env python

import cdsapi

c = cdsapi.Client()

c.retrieve(
    'reanalysis-era5-pressure-levels',
    {
        'product_type': 'reanalysis',
        'variable': 'temperature',
        'pressure_level': '1000',
        'year': '2008',
        'month': '01',
        'day': '01',
        'time': '12:00',
        'format': 'netcdf',                 # Supported format: grib and netcdf. Default: grib
    },
    'download.nc')                          # Output file. Adapt as you wish.



  2. 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.


    • Expand
      titleClick here for a sample script (for ERA5 1940-present) that downloads temperature at a given pressure level at 1000 hPa for a geographical subset of the data and specified grid


      Code Block
      languagetext
      #!/usr/bin/env python
import cdsapi

c = cdsapi.Client()

c.retrieve(
    'reanalysis-era5-pressure-levels',
    {
        'product_type': 'reanalysis',
        'variable': 'temperature',
        'pressure_level': '1000',
        'year': '2008',
        'month': '01',
        'day': '01',
        'time': '12:00',
        'format': 'netcdf',                 # Supported format: grib and netcdf. Default: grib
        'area'          : [60, -10, 50, 2], # North, West, South, East.          Default: global
        'grid'          : [1.0, 1.0],       # Latitude/longitude grid.           Default: 0.25 x 0.25
    },
    'era5_temperature_sub_area.nc')         # Output file. Adapt as you wish.



To retrieve data efficiently using the CDS API please have a look at the efficiency tips section on CDS documentation.


Note
titleRequests 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 stored on MARS tape archive (no data selection can be made from the CDS download form) - 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 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 10petabyte) 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, except for the latest couple of months of ERA5-complete, which are also kept online.


Note

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 (1940-present) and learn how to build a CDS API request by following these steps:

  1. Open the MARS ERA5 catalogue

  2. browse for discovery, and browse your way to the parameter level to build a request.

    Info
    • 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.
    • The MARS catalogue only shows data for the final quality controlled data that is made available 2-3 months in arrear. However, data is also available from preliminary timely updates up to 5 days behind real time, using the same retrieval structure.


    Note

    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.


  3. 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.

    Expand
    titleExample: Download ERA5 model level analysis data (temperature) in the native spherical harmonics representation in GRIB format.


    Code Block
    #!/usr/bin/env python
import cdsapi
c = cdsapi.Client()
c.retrieve('reanalysis-era5-complete', { # Requests follow MARS syntax
                                         # Keywords 'expver' and 'class' can be dropped. They are obsolete
                                         # since their values are imposed by 'reanalysis-era5-complete'
    'date'    : '2013-01-01',            # The hyphens can be omitted
    'levelist': '1/10/100/137',          # 1 is top level, 137 the lowest model level in ERA5. Use '/' to separate values.
    'levtype' : 'ml',
    'param'   : '130',                   # Full information at https://apps.ecmwf.int/codes/grib/param-db/
                                         # The native representation for temperature is spherical harmonics
    'stream'  : 'oper',                  # Denotes ERA5. Ensemble members are selected by 'enda'
    'time'    : '00/to/23/by/6',         # You can drop :00:00 and use MARS short-hand notation, instead of '00/06/12/18'
    'type'    : 'an',
}, 'output')                             # Output file; in this example containing fields in grib format. Adapt as you wish.



  4. Tailor your request to
    1. re-grid to the desired regular lat-lon resolution
    2. convert to NetCDF (works for regular grids only, i.e., so you need to use the 'grid' keyword as well)

    3. select sub areas


      Expand
      titleExample to download model level ERA5 analysis data (temperature) for a given area at a regular lat/lon grid in NetCDF format.


      Code Block
      #!/usr/bin/env python
import cdsapi
c = cdsapi.Client()
c.retrieve('reanalysis-era5-complete', { # Requests follow MARS syntax
    5. Build the basic CDS API request.
    As described in on How to migrate from ECMWF Web API to CDS API, you can use the CDS web interface to help you build your CDS API download script. In the download form, make some selections, then click the button Show API request and you will be presented with the script.
    Expand
    titleBasic CDS API script example to download temperature at a given pressure level, 1000 hPa is shown HERE.
    Code Block
    languagetext
    #!/usr/bin/env python import cdsapi c = cdsapi.Client() c.retrieve('reanalysis-era5-pressure-levels', { 'variable' : 'temperature', 'pressure_level': '1000', 'product_type' : 'reanalysis', 'year'
    1.
    6. :
    1.
    7. '2008', 
    1.
    8. 'month'
    1.
    9. :
    1.
    10. '01', 
    1.        # Keywords '
    11. day
    1. expver' and 'class' can be dropped. They are obsolete
    12. :
    1.
    13. '01', 
    1.
    14. 'time'
    1.
    15. :
    1.
    16. '12:00', 
    1.
    17. 'format'
    1.
    18. :
    1.
    19. 'netcdf'
    1.  # since
    20. Supported
    1. their
    21. format:
    1. values
    22. grib
    1. are
    23. and
    1. imposed
    24. netcdf. Default: grib 
    1. by 'reanalysis-era5-complete'
    25. },
    1.  '
    26. test.nc') Refining your CDS API script for ERA5 data listed in CDS.
    Currently the interactive CDS forms don't allow users to perform a regional sub-selection or an interpolation of the selected data. However, both actions can be performed using the following CDS API keywords:
  26. For a geographical area subset, use key area.
    27. For a different grid resolution, use key grid.
    Please note that the ERA5 native grid in 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).
    Below is a sample script for downloading temperature at a given pressure level, 1000 hPa. It also shows how to request for a geographical subset of the data.
    Expand
    titleShow basic CDS API script including geographical subset
    Code Block
    languagetext
    #!/usr/bin/env python import cdsapi c = cdsapi.Client() c.retrieve('reanalysis-era5-pressure-levels', { 'variable' : 'temperature
    1. date'    : '2013-01-01',            # The hyphens can be omitted
    'levelist': '1/10/100/137',          # 1 is top level, 137 the lowest model level in ERA5. Use '/' to separate values.
    'levtype' : 'ml',
    
    1. 'param'
    29. 'pressure_level'
    1. : '
    30. 1000
    1. 130',
    1.
    32. 'product_type'
    1.
    33. :
    1.
    34. 'reanalysis', 
    1.
    35. 'year'
    1. # Full information at https://apps.ecmwf.int/codes/grib/param-db/
    36. :
    1.
    37. '2008', 
    1.
    38. 'month' 
    1.
    39. :
    1.
    40. '01', 
    1.
    41. 'day'
    1.         # The native
    42. : '01', 
    1. representation for temperature is spherical harmonics
    '
    43. area
    1. stream'  : 'oper',
    44. :
    1.
    45. [60,
    1.
    46. -10,
    1.
    47. 50,
    1.
    48. 2],
    1.
    49. #
    1.
    50. North,
    1.
    51. West,
    1.
    52. South,
    1.
    53. East.
    1.
    54. Default:
    1.
    55. global 
    1. # Denotes ERA5. Ensemble members are selected by '
    56. grid
    1. enda'
    
    1. 'time'    :
    58. [1.0, 1.0], # Latitude/longitude grid: east-west (longitude) and north-south resolution (latitude). Default: 0.25 x 0.25 'time' 
    1. '00/to/23/by/6',         # You can drop :00:00 and use MARS short-hand notation, instead of '00/06/12/18'
    'type'    : '
    59. 12:00
    1. an',
    'area'    : '
    60. format'
    1. 80/-50/-25/0',
    61. :
    1.
    62. 'netcdf'
    1.  #
    63. Supported format: grib and netcdf
    1. North, West, South, East. Default:
    64. grib
    1. global

    1.
    66. },
    1.  '
    67. test.nc')

Step C: Download ERA5 data NOT listed in CDS through CDS API

...

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...

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. In most cases, this means retrieving all the data you need for one month, then for the next month, and so on. To find out what data is available on each tape, browse the ERA5 Catalogue and make your way until the bottom of the tree archive (where parameters are listed). Once you will have reached that level of the archive, what you see is what you can find on one single tape. See Retrieval efficiency page for more details.

Transpose the MARS keywords into the CDS API script as shown on the examples below (please note that you need to give  'reanalysis-era5-complete ' as the dataset name in your script) :

...

titleExample 1: Download model level forecast ERA5 data (temperature) for a given area at a regular lat/lon grid in NetCDF format.
    1. grid'    : '1.0/1.0',               # Latitude/longitude. Default: spherical harmonics or reduced Gaussian grid
    'format'  : 'netcdf',                # Output needs to be regular lat-lon, so only works in combination with 'grid'!
}, 'ERA5-ml-temperature-subarea.nc')     # Output file. Adapt as you wish.



For ERA5.1-complete follow the same procedure as for era5-complete explained above, however:

Warning

Please read: Technical issue fixed on ERA5.1 CDS API

  1. edit the script to change:


    Code Block
    'reanalysis-era5-complete' to 'reanalysis-era5.1-complete'


data is only available for the years 2000-2006 inclusive - so make sure that your request dates are within this time period.


Expand
titleExample to download ERA5.1 monthly mean temperature at 50 hPa at a regular lat/lon grid in NetCDF format.


Code Block
#!/usr/bin/env python
import cdsapi
c = cdsapi.Client()
c.retrieve('reanalysis-era5.1-complete', { # Please note the addition '.1' for ERA5.1!
                                           # Keywords 'expver' and 'class' can be dropped. They are obsolete
                                           # since their values are imposed by 'reanalysis-era5.1-complete'
    'date': '2005-01-01',                  # Valid range:  2000-01-01 to 2006-12-31. Always first of the month for monthly means

...


    'levelist': '

...

50

...

',

...

...

...

...

...

...

...

...

...

#

...

Pressure level at 50 hPa
    'levtype': '

...

pl',
    'param': '

...

130.128',

...

...

...

...

...

...

...

...

...

...

...

...

...

...

...

 # Full

...

titleExample 2: Download ERA5 model level analysis data (temperature) at the default reduced Gaussian grid in GRIB format.

...

information at https://apps.ecmwf.int/codes/grib/param-db/
    'stream': 'moda',                      #

...

Monthly means (of Daily means).
    '

...

type'

...

: '

...

an',
    '

...

grid'    : '1.0/1.0',                 # Latitude/longitude grid resolution.
    '

...

format'  : '

...

netcdf',

...

...

...

...

...

...

...

  # Output

...

needs

...

to be regular lat-lon, so only works in combination with 'grid'!
}, 'era5.1-temperature-monthly-mean.nc')





Info
iconfalse

This document has been produced in the context of the Copernicus Climate Change Service (C3S).

The activities leading to these results have been contracted by the European Centre for Medium-Range Weather Forecasts, operator of C3S on behalf of the European Union (Delegation Agreement signed on 11/11/2014 and Contribution Agreement signed on 22/07/2021). All information in this document is provided "as is" and no guarantee or warranty is given that the information is fit for any particular purpose.

The users thereof use the information at their sole risk and liability. For the avoidance of all doubt , the European Commission and the European Centre for Medium - Range Weather Forecasts have no liability in respect of this document, which is merely representing the author's view

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