Before proceeding with the steps below, users must be ECMWF registered and have their computer set up as described on How to download data via the ECMWF WebAPI.
1. Learn about C3S Seasonal forecast data
- Read about .
- Browse the C3S Seasonal Forecast data catalogue and make sure the data you are interested in is available.
- Copernicus User Support team for assistance with C3S Seasonal data selection. is currently in preparation and will be made available as soon as possible to help users with parameters (fields), values for data type, stream, level type (surface, pressure levels, model levels, etc) , forecast steps, etc... In the meantime, users may contact the
- See known issues of the C3S seasonal forecast
2. Copernicus License agreement
Read the Copernicus license agreement and accept it at the bottom of the page.
3. Run a C3S Seasonal forecast test retrieval script
This is to verify that your computer is set up correctly.
Copy the Python script below to a text file and save it, for example as "test.py"
- Run the script. On most computers you would do this by opening a command prompt and typing
The test request will download data from ECMWF and save as file "test.nc" in the directory you issued the command from. The file should be around 535 KB.
Note that the data retrieval is not designed to be instant. The test request above usually takes a few minutes to complete, but depending on demand can take longer.
4. Create your custom C3S Seasonal forecast data retrieval script
- Browse the C3S Seasonal Forecast data catalogue for the data you are interested in, and in the last step make a selection in all boxes and click 'View the MARS request' and make sure the Python Script tab is displayed. This shows a template Python script with your selected options.
- Copy the template Python script to a text file and save it, for example as 'my_multi-model-seasonal-forecast_script_v1.py'
- Adapt the template Python script to your requirements, taking the following remarks into account:
- In most cases, you will have to add lat/lon "grid" in your script, e.g., "grid": "1.0/1.0". This will enable you to download data on a regular lat/lon grid. And this is necessary if you download the data in NetCDF format.
- For an output in NetCDF format, add
in your script. By default, output will be in GRIB format. Notice if you retrieve forecast data in NetCDF, please be aware of this potential issue.
- If you specify
, the horizontal resolution is in decimal degrees. For more details, see this link. If not set, the archived grid as specified in the data documentation is used.
- If you do not want global data, you can add
as N/W/S/E in lat/lon degrees. Southern latitudes and western longitudes must be given as negative numbers, e.g.,
. If you set "area", you should also
add a lat/lon
as shown in c.this link.
grid, e.g., "grid": "1.0/1.0",
- If you are retrieving forecast data (
), make sure that
are specified. Note that if
is set to
is the time of the forecast.
,to the desired output path and file name, e.g.
"./data/data1.grib". The default path is the current working directory.
5. Run your data retrieval script
On most computers you would do this by opening a command prompt and typing
This will retrieve the data as specified and download it as a single file to your computer into the current directory (or whichever "target" directory you specified).
Note that the data retrieval is not designed to be instant. A larger request can take hours and even days to complete.
For long running processes you can check the progress of your request in your job list.
To report an issue or bug please contact Copernicus Support at ECMWF.