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1. As a starting point, browse the ERA-Interim 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". This shows a template Python script with your selected options.
2. Copy the template Python script to a text file and save it, for example as 'my_ERA-Interim_script_v1.py'.
3. Adapt the template Python script to your requirements, taking the following remarks into account:
   1. 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.
   2. For an output in NetCDF format, add "format": "netcdf" 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.
   3. If you specify "grid", 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.
   4. If you do not want global data, you can add "area" asN/W/S/E in lat/lon degrees. Southern latitudes and western longitudes must be given as negative numbers, e.g., "area": "75/-20/10/60". If you set "area", you should also add a lat/lon grid, e.g., "grid": "1.0/1.0", as shown in c. For more details about "area", see this link.
   5. If you are retrieving forecast data ("type":"fc"), make sure that "steps" are specified. Note that if "type" is set to "fc", then "time" is the time of the forecast.
   6. Change the "target": "CHANGEME", to the desired output path and file name, e.g.  "data1.nc" or "./data/data1.grib". The default path is the current working directory.

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