ERA5 Radiation does NOT look accumulated, despite the description. Potential bug?

Dear all,

I have found a potential inconsistency in the Thermal Net Radiation. The description for this variable in ERA5 says:

This parameter is accumulated over a particular time period which depends on the data extracted. For the reanalysis, the accumulation period is over the 1 hour ending at the validity date and time

The description for this variable in ERA5 LAND says:

Accumulated field from the beginning of the forecast time to the end of the forecast step.

However, when plotting these data, they look different. Let me show it:


  • Blue line is ERA5 hourly data for Surface Net Thermal Radiation
  • Orange line is the same data, but resampled to a daily resolution by adding all the values
  • Green line with stars is ERA5 LAND hourly data for the same variable. This is clearly a cumulative curve, as it shows a strong discontinuity when the date changes.

Is this a bug? Am I missing something?