We are pleased to announce that the first version of the Comprehensive Upper-air Observation Network from 1901 to present dataset has been published on 27 November 2025, in the Climate Data Store (CDS):
This dataset is the first of its kind on the CDS, covering the global observation records obtained from balloon ascents from so many sources. It results from several years of data consolidation and data analysis carried out by an international team, in collaboration with international observation archives.
Although most reports are from the 1950s onwards, the time coverage extends to the beginning of the 20th century. This dataset is also one of the key observation datasets input to the upcoming ERA6 global reanalysis.
For more details please have a look at the documentation.
Please let us know of any additional relevant observation data holdings that are presently missing in this dataset, and could contribute to enrich future iterations.
For any enquiries and feedback regarding this dataset, please contact us.
ECMWF Support