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- Analyses are produced by combining short-range forecast data with observations to produce the best fit to both. The data are available a few times per day.
- Instantaneous forecast data are produced by the forecast model, starting from an analysis, and are available at various forecast steps (hours) from the analysis date/time. (Note, forecasts are only initiated from analyses 00 and 12). These data are relevant to a particular verifying validity date/time (analysis forecast start date/time plus step).
- Accumulated forecast parameters are accumulated over particular periods. In some datasets the period will be from the beginning of the forecast (eg in ERA-Interim), while in ERA5 the period is since the previous post processing (archiving). You can divide values by the length of the forecast step accumulation period to calculate averages over the accumulation period.
- Minimum or maximum forecast parameters are the minimum or maximum during a particular period.
Some parameters are only analysed, some are only forecast (e.g. radiative fluxes) and some are both analysed and forecast (e.g. temperature, winds and pressure).
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