Cause of the error:

This is known issue when downloading data in the NetCDF format:

For example, you select all times (00:00, 06:00, 12:00, 18:00) and you select all steps (0 to 120 in 3-hour steps).

In this case you will get data for:

2016-12-01, 00:00 (time 00:00 + step 0)

2016-12-01, 03:00 (time 00:00 + step 3)

2016-12-01, 06:00 (time 00:00 + step 6)

2016-12-01, 06:00 (time 06:00 + step 0)

2016-12-01, 09:00 (time 06:00 + step 3)

... and so on.

So in this example you get two values at validity time 2016-12-01, 06:00.

The NetCDF format only supports a single, one-dimensional time dimension, so a specific time can not have two Ozone values say.

This is why trying to retrieve this data in NetCDF format results in an error.

Possible workarounds

• Use the data's native GRIB format . This i.e. download the data in GRIB format and then convert the data file yourself following guidelines. GRIB format supports multiple data values at any one validity time.
• If you are only interested in the analysis, but not forecasts, download data only for step 0
• If you need overlapping forecast, download for each time option separately, for example:
  • first with time = 00:00 and all required steps
  • then with time = 06:00 and all required steps
  • then with time = 12:00 and all required steps
  • then with time = 18:00 and all required steps