AOPC Working Group on GRUAN



The GCOS/WCRP Atmospheric Observation Panel for Climate (AOPC ) Working Group on GRUAN (WG-GRUAN), formerly named Working Group on Atmospheric Reference Observations (WG-ARO), was established in 2006 in recognition of the importance of initiating reference-quality observations of vertical profiles of essential climate variables from the surface into the stratosphere to enhance monitoring and understanding of climate variability and change.

The 2004 GCOS Implementation Plan identified the establishment of a reference-quality network as “a very high priority”. The 2010 Update of the GCOS Implementation Plan (GCOS-138) reiterated the call for the establishment of the GCOS Reference Upper-Air Network (GRUAN) for reference upper-air measurements and a complementary system for reference measurements from satellites, and support of reanalysis and reprocessing activities as a key need. Since 2008, the German Meteorological Service, Deutscher Wetterdienst (DWD), have been hosting the GRUAN Lead Centre, consisting of scientific and secretarial support at their Lindenberg Observatory to oversee day-to-day operations of the network. Involvement of WMO in GRUAN operations occurs through representatives from relevant WMO Technical Commissions as ex-officio members on the WG-GRUAN. The initial GRUAN Implementation Plan (GCOS-134), published in 2009, is superseded by the new GRUAN Implementation Plan, covering the period 2013-2017, published in January 2013 (GCOS-165).

It is the Working Group’s responsibility to facilitate this implementation, liaising with other groups and national and international bodies to ensure that an eventual GRUAN is fit for purpose, robust and has the required long-term commitment and management structures. The WG-GRUAN also provides guidance to the GRUAN Lead Centre. The WG-GRUAN membership consists of a broad range of scientific and technical experts who contribute expert oversight and support to GRUAN development and operations.

The AOPC, supported by the GCOS Secretariat, and guided by the GCOS Steering Committee, provides direction and oversight of GRUAN. The WG-GRUAN provides direct guidance on the operation of GRUAN and is supported by specific GRUAN Task Teams. A GRUAN Scientific Coordinator guides the initiation and undertaking of specific research projects in support of GRUAN operations. The day-to-day management and coordination of the network, including training and ensuring the archival and dissemination of GRUAN data, is the responsibility of the GRUAN Lead Centre.

Working group roles and responsibilities

The working group has a range of roles and responsibilities that reflect the GCOS and WMO expectations of its outputs. Here, these have been arranged under broad categories that reflect the core facets of the expected work.


  • To provide scientific, technical and management oversight of the operations of the GRUAN Lead Centre, which will manage the overall work and evolution of the network, and which shall report to the WG-GRUAN at least twice a year;

  • To define roles and responsibilities of the GRUAN Lead Centre and, as deemed appropriate, other centres, for data management, quality monitoring, analysis and capacity development purposes;

  • To initiate, approve, manage and dissolve, as appropriate, task teams established to undertake specific activities in support of GRUAN;

  • To encourage and support the activities of GATNDOR and provide feedback and input as requested by that team;

  • To ensure that GRUAN operations are well aligned with the goals and directions of GCOS through liaison with the AOPC;

  • To ensure that GRUAN operations are well aligned with WMO goals and directions through the representatives of WMO Technical Commissions;

Site selection, assessment, and certification

  • To define essential and desirable requirements of a GRUAN site in terms of operational principles, the collection of metadata, assessment of measurement uncertainties, data management, variables addressed, and instrumentation. Develop these requirements in consultation with other relevant observing programmes, make them publically available, and periodically reassess their validity;

  • To certify sites based on (i) information submitted by the site, (ii) an assessment made by the Lead Centre, and (iii) potentially on-site assessment by WG and/or Lead Centre members, against the set of requirements. Periodically reassess/audit sites against these same requirements;

  • To decide on the composition of GRUAN, including the selection of sites. This should be done in consultation with AOPC and other advisory bodies as appropriate;


  • Together with relevant stakeholders, to plan and realize annual Implementation and Coordination Meetings (ICMs) to be hosted at, or associated with, a GRUAN site and to include a site visit;

  • To report at least annually to AOPC on its activities, including the progress towards a reference network, the performance of the network once established, the uses and value of the data collected, and the implications for the global observing system;

  • To ensure that the GRUAN Implementation Plan and individual work plans from ICM meetings are carried out, including but not limited to undertaking those activities mandated to the WG-GRUAN;

  • To evaluate 6-monthly progress reports from the Lead Centre and GRUAN Task Teams and provide feedback in a timely manner;

Advocacy and outreach

  • To work with relevant agencies and programmes to define and promote GRUAN for long-term atmospheric reference observations of a range of specific variables, and to make optimal use of existing and planned infrastructure within the WMO Global Observing System. This includes inter alia, working with the WIGOS planning office as a WIGOS pilot project; the WMO Space Programme, Commission on Basic Systems (CBS) and CIMO on satellite and radiosonde calibration and validation issues, including reference instrumentation and metadata;

  • To provide for appropriate communication and outreach activities (through such activities as conferences, making connections with other programmes, organizing special conference sessions on GRUAN etc.).

  • To work with strategic partner organizations and projects as specified from time to time inter-alia by AOPC, in annual Implementation and Coordination Meetings or in the GRUAN Implementation Plan.

Mode of operation

  • The Chair or Co-chairs will be appointed by the AOPC.

  • Working Group members will be approved by the AOPC.

    • Co-chairs from each Task Team and from GATNDOR are expected to be members.

    • At least one member will explicitly represent each of the four WMO Technical Commissions associated with GRUAN.

    • At least one expert in the following fields shall be present to ensure a plutocracy of views:

      • Climate science

      • In-situ atmospheric observations

      • Satellite observations

      • NWP / reanalyses

      • Statistics

      • Metrology

    • Members may fulfil multiple roles, but AOPC needs to be mindful of any potential conflicts of interest that may arise as a result.

    • The AOPC decides at its annual meetings on additional experts and observers to join the WG-GRUAN as ex-officio or full members.

  • Members will be expected to serve for at least two years or until the membership is reviewed.

  • During the GRUAN implementation phase it is envisaged that annual WG-GRUAN meetings will be convened together with ICMs (see above), which group members will be expected to attend. Funding to support in part or in full WG-GRUAN meetings should be sought from sponsors.

  • The WG-GRUAN will generally correspond by e-mail and teleconferences (to be undertaken every other month), and take advantage of relevant workshops and conferences to hold meetings (in addition to meeting at the time of ICMs). Additional meetings will be convened by the Chair(s) upon demand, in consultation with the GCOS Secretariat and GRUAN partner institutions.

  • These Terms of Reference will be subject to periodic review by AOPC in liaison with the Co-chairs of the Working Group and the Lead Centre.


as at October 2023

Members *

Fabio Madonna (co-chair) CNR - IMAA, IT ()
Masatomo Fujiwara (co-chair) Hokkaido University, JP ()
Arnoud Apituley KNMI, NL
Alessandro Fasso University of Bergamo, IT
Tom Gardiner National Physical Laboratory, UK
Thierry Leblanc NASA/JPL, US
Kalev Rannat Tallinn University of Technology, EE
Bomin Sun NOAA, US
Krunoslav Premec WMO, CH
Imke Durre NOAA, US
Howard Diamond NOAA, US
Erik Anderson ECMWF, UK
Richard Querel NIWA, Lauder, NZ
Caterina Tassone WMO, CH
Lori Borg University of Wisconsin, Madison, US
Tim Oakley WMO, CH
Evan Keeler ARM, US
Graziano Coppa INRIM, IT
Jonathan Jones MetOffice, UK
Axel von Engeln EUMETSAT, DE
Marion Maturilli AWI, DE
Nico Cimini University of L'Aquila, IT
Christoph von Rohden DWD, DE
Ryan Stauffer NASA, US

GRUAN Lead Centre representative

GRUAN Lead Centre representative
Ruud Dirksen DWD, Germany ()

* ‘Members’ serve in their personal capacity as experts, whereas ‘ex-officios’ serve in their respective role, representing organizations or programmes.