GRUAN

GRUAN is an international reference network of about thirty stations dedicated to the observation of key climatological variables between the surface and the stratosphere by radiosoundings.

Several French organisations have been actively collaborating for 36 months to certify two major sites: a site in Ile-de-France comprising the Météo-France radiosonde station in Trappes and the SIRTA Observatory in Palaiseau, and a site in Reunion Island comprising the Météo-France radiosonde station in Saint-Denis de la Réunion and the Maïdo Observatory (OPAR). Each site is based on the complementarity of the observations made: vertical measurements by radiosondes on the one hand, and active and passive remote sensing measurements on the other.

This working collaboration is based on IPSL (project management, algorithmic developments and SIRTA Observatory), MétéoFrance (radiosonde production), the national data centre AERIS (archiving, processing and database), OSU-Réunion and LACy (Maïdo Observatory, intercomparisons) and the company Météomodem (radiosonde equipment manufacturer).
The GRUAN certification documents for the French sites were sent to the GRUAN Lead Center in September 2020.

This certification is a guarantee of the quality of the radiosondes used (Meteomodem M10 probe) and of the associated sites equipped with automatic radiosonde launchers.

Indeed, GRUAN-certified probes are finely characterised with quantified uncertainties and perfect traceability of performance and possible drifts. The same applies to sites implementing validated, reproducible and documented procedures over the long term (action taken by MétéoFrance).

A major result of this certification work is the production of a technical document describing each correction and associated uncertainty, as well as the validation of the results (several hundred hours of tests and measurement campaigns in various European laboratories, in temperate and tropical environments, enabling the development of
parameterisations to optimise the vertical profiles of humidity, temperature, pressure or wind, and thus develop the final GRUAN product (Dupont et al., 2020²). A first dataset is available on the GRUAN website.

During this certification work, significant work was also carried out on data flows to ensure an optimised supply of processed and documented data in NetCDF format from the initial 6 files in ascii format.
Obtaining this GRUAN certification is important for the French observation stations: it is a guarantee of the quality of the measurements carried out there, a quality that is essential for their use by national and international scientific teams for their studies on physicochemical processes as well as for the analysis of atmospheric trends in a climate change context.

Source : Jean-Charles DUPONT (Institut Pierre-Simon Laplace) Météo et Climat Info n°78

(1) F. Madonna, R. Kivi, M. Fujiwara, B. Ingleby, G. Romanens, M. Hernandez, X. Calbet, M. Rosoldi, A. Giunta, T. Karppinen J-C. Dupont, M. Iwabuchi, S. Hoshino, C. von
Rohden, P. W. Thorne, Use of automatic radiosonde launchers to measure temperature and humidity profiles from the GRUAN perspective, 2020, AMT, amt-2019-472
(2) J.-C. Dupont, Haeffelin M., Badosa J., Vignelles D., Raux C., Clain G., 2020, Characterization and Corrections of Relative Humidity Measurement from Meteomodem M10
Radiosondes at Midlatitude Stations, JAOT, Vol. 37, p. 8547-871, DOI: 10.1175/JTECH-D-18-0205.1