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Mean rates/fluxes and accumulations
Such parameters have undergone particular types of statistical processing (temporal mean or accumulation) over a period of time called the processing period. These parameters may, or may not, have been averaged in time, to produce monthly means, for example.
The accumulations (over the accumulation/processing period) in the short forecasts (from 06 and 18 UTC) of ERA5 are treated differently compared with those in ERA-Interim and operational data (where the accumulations are from the beginning of the forecast to the validity date/time). In the short forecasts of ERA5, the accumulations are since the previous post processing (archiving), so for:
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