ECMWF open data: file naming and formats

File format

Fields are in GRIB edition 2; tropical-cyclone tracks are in BUFR edition 4. We recommend ecCodes version 2.42.0 or newer to read them.

[ROOT]/[yyyymmdd]/[HH]z/[model]/[resol]/[stream]/[yyyymmdd][HH]0000-[step][U]-[stream]-[type](-[levtype]).[format]

Field	Meaning
`[ROOT]`	Top-level URL of a hosting location (see Where to get it on the overview page)
`[yyyymmdd]`	Reference (base) date of the forecast
`[HH]`	Reference time: 00, 06, 12 or 18
`[model]`	Production model: `ifs`, or an AIFS model (see the AIFS page)
`[resol]`	Horizontal resolution: `0p25` or `0p1`
`[stream]`	Forecasting system: see the What's available table (`scda`/`scwv` retired at 50r1)
`[step]` / `[U]`	Forecast step and its unit: `h` for hours, `m` for months (seasonal only)
`[type]`	Forecast type: `fc`, `ef`, `ep`, `tf`, etc.
`[levtype]`	Level type — 0.1° only: `sfc` (surface fields) or `pl` (pressure-level fields). The 0.25° tier is a single combined file and carries no suffix.
`[format]`	`grib2` for fields, `bufr` for tracks, `index` for metadata

AIFS products use a different file-naming convention from the IFS — see the AIFS page.

There are minor differences between the normal MARS request language and the open-data file names, summarised here for information.