Met Office DataPoint / CEDA
CEDA, the Centre for Environmental Data Analysis, is the UK's national archive for atmospheric and Earth observation data. It brings together Met Office observational records, UK and global climate model outputs (including runs from the CMIP projects that feed the IPCC assessments), satellite and airborne remote-sensing data, and measurements from long-running research campaigns. The archive is large and scientific in nature: think gridded model output, station records, and imagery rather than tidy prose.
Access is through the CEDA Archive and its catalogue at data.ceda.ac.uk. Much of the data is openly downloadable, but a good deal sits behind a free CEDA account, and some collections require you to apply and agree to specific terms first. Files come in scientific formats such as NetCDF, HDF, GRIB, and CSV, and you can pull them over HTTP or FTP or, for large jobs, work with them on CEDA's own JASMIN analysis platform rather than moving terabytes around.
For RAG, the honest framing is that CEDA is a source of data, not documents. The numeric climate and observation files are not something you embed directly. The valuable text lives in the surrounding metadata, dataset catalogue records, documentation, and provenance, which you can index to build a system that helps people discover which dataset answers their question and how to use it. The Met Office DataPoint style forecast and observation feeds are similarly better as structured facts you summarise into passages than as raw text.
Watch the licensing, which varies by dataset. Much of the archive is under the Open Government Licence, which permits reuse including commercial use as long as you attribute the source, but individual collections carry their own terms, and some are restricted, so check each dataset before you build on it and always credit it. As a companion, the AWS and Google public cloud archives host overlapping satellite and climate collections in cloud-optimised formats; CEDA is the place to go for UK-focused and Met Office material specifically.
Related sources
Copernicus (EU Earth Observation)
The EU's flagship Earth observation programme. The Copernicus Climate Change Service portal provides authoritative information about past, present, and future global climate, derived from Sentinel reference products alongside other satellite observations and in-situ measurements.
NASA Earthdata
The home for full and open access to NASA's Earth science data collections. The umbrella portal for the largest collection of freely available Earth science data in the world, with over 12,400 datasets spanning land, ocean, atmosphere, and cryosphere, collected by satellite missions, airborne campaigns, and ground stations.
NOAA Open Data Dissemination (NODD)
Free, full, and open access to NOAA data through partner platforms including Amazon Web Services, Google, and Microsoft Azure. Covers climate data records and atmospheric, oceanic, and terrestrial datasets from one of the largest climate archives in the world.
WeatherBench 2
Google Research's open benchmark and curated ERA5-derived data archive for evaluating data-driven global weather models over the one-to-fifteen-day range. It bundles an Apache-licensed evaluation framework, cloud-hosted ground-truth and baseline forecast datasets in Zarr, and a continuously updated leaderboard ranking models such as GraphCast and Pangu-Weather against ECMWF's IFS.