GCOS Reference Upper-Air Network

The climate reference network

The Global Climate Observing System (GCOS) Reference Upper-Air Network (GRUAN) is an international reference observing network of sites measuring essential climate variables above Earth's surface, designed to fill an important gap in the current global observing system. GRUAN measurements are providing long-term, high-quality climate data records from the surface, through the troposphere, and into the stratosphere. These are being used to determine trends, constrain and calibrate data from more spatially‐comprehensive observing systems (including satellites and current radiosonde networks), and provide appropriate data for studying atmospheric processes. GRUAN is envisaged as a global network of eventually 30-40 sites that, to the extent possible, builds on existing observational networks and capabilities.

GRUAN promotional video

This video provides an excellent overview of the goals and principles of GRUAN and its relation to the current challenges in climate research. You can find this and other public outreach material here.

Status of GRUAN sites

GRUAN is envisaged as a global network of eventually 30-40 measurement sites. To the extent possible, it builds on existing observational networks and capabilities. As at March 2024, GRUAN comprises of 33 sites, 14 of which have been GRUAN certified.

Status of data flow

A comprehensive volume of measurement data has been collected by GRUAN since 2008. The archive includes raw data and related meta-data. For the Vaisala RS41 & RS92 and the Meisei iMS-100 & RS-11G radiosondes, GRUAN Data Products (GDP) have been fully implemented and certified. Further GDPs are in certification process or under development.

Latest news


ICM-15 meeting report published

The report of the GRUAN ICM-15 meeting is available for download.


EGUsphere paper Sugidachi et al. 2024 in review

The following GRUAN-relevant paper was published at EGUsphere [preprint]: "Development of a Peltier-based chilled-mirror hygrometer for tropospheric…


Report of WMO’s 2022 Upper-Air Instrument Intercomparison Campaign (IOM-143) published

The report of the UAII2022 radiosonde intercomparison campaign has been published by WMO.


ICM-15: 11 - 15 March 2024 in Bern, Switzerland

The ICM-15 took place from March 11 to 15, 2024 in Bern, Switzerland. All presentations are now available.


Atmosphere paper Mashao et al. 2024 published

The manuscript "An Appraisal of the Progress in Utilizing Radiosondes and Satellites for Monitoring Upper Air Temperature Profiles" has been published…


RS paper Rannat et al. 2023 published

The manuscript "The Novel Copernicus Global Dataset of Atmospheric Total Water Vapour Content with Related Uncertainties from GNSS Observations" by…


AMT paper Faber et al. 2023 published

The manuscript "Acquiring high-resolution wind measurements by modifying radiosonde sounding procedures" by Faber et al. has been published on…


Axioms paper Fassò et al. 2023 published

The manuscript "On the Kalman Smoother Interpolation Error Distribution in Collocation Comparison of Atmospheric Profiles" by Fassò et al. has been…


GRUAN Technical Note 14 published

GRUAN Technical Note 14 (GRUAN-TN-14) published with title "GRUAN Policy on Silent Sites"


GCOS-253 - GRUAN Implementation Plan 2024-2030 published

The GRUAN Implementation Plan 2024-2030 is available for download.  

Document Data product

RS41 GRUAN Technical Document 8 (GRUAN-TD-8) published

The GRUAN Lead Centre announces the publication of the Technical Document (GRUAN-TD-8) on version 1 of the GRUAN data product for the Vaisala RS41…