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 November 2022, GRUAN comprises of 31 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


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…


ICM-15 mid-March 2024 in Switzerland

ICM-15 is provisionally scheduled for mid-March 2024, and will either be 11-15 March, or 18-22 March. We will announce once the exact dates and venue…


UAII2022 field campaign

The field campaign of UAII2022 was successfully executed between 8 August and 13 September. In this period, more than 80 balloons were launched,…


AMT paper Trent et al. 2023 published

The manuscript "Evaluation of tropospheric water vapour and temperature profiles retrieved from MetOp-A by the Infrared and Microwave Sounding scheme"…


RS paper Wee et al. 2022 published

The manuscript "Atmospheric GNSS RO 1D-Var in Use at UCAR: Description and Validation" by Wee et al. has been published on Remote Sensing.


RS paper Zhang et al. 2023 published

The manuscript "Assessment of AIRS Version 7 Temperature Profiles and Low-Level Inversions with GRUAN Radiosonde Observations in the Arctic" by Zhang…


Nature article to high-altitude balloons

High-altitude balloons: a scientists’ guide to what’s up there and why. The US has shot down four flying objects over fears of spy balloons. But what…


ACP paper Prange et al. 2023 published

The manuscript "How adequately are elevated moist layers represented in reanalysis and satellite observations?" by Prange et al. has been published on…


ICM-14 meeting report published

The report of the GRUAN ICM-14 meeting is available for download.

Data product

GRUAN certification for RS41 GRUAN Data Product Version 1 (RS41-GDP.1)

The RS41 GRUAN Data Product Version 1 (RS41-GDP.1) has been certified by GRUAN.