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Archived data may originate from e.g. routine operations (od), from research experiments (rd), reanalysis data sets (e.g. e5 for ea for ERA5), TIGGE (ti) , S2S (s2) or experiments created by Member State users (Internet country code, e.g. uk, es,...). Operations and reanalysis are the most frequently used data classes. A full list of ECMWF classes is available online.
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