The GCOS Reference Upper-Air Network (GRUAN) MANUAL


World Meteorological Organization (WMO)

Last version

v1.1 (2013-03)







This GCOS (Global Climate Observing System) Reference Upper‐Air Network (GRUAN) Manual describes mandatory operating protocols (distinguished by use of the words “must” or “shall”) which describe what is expected of participating sites, the GRUAN Lead Centre, and the Working Group on GRUAN (WG‐GRUAN) to achieve the goals of GRUAN. These protocols have the status of requirements in a technical resolution, which sites within GRUAN are expected to follow or implement.

Sites that operate under the protocols outlined in this Manual are recognized as being state‐of‐ the‐art measurement sites that support the core goals of GCOS. Given the high profile of GCOS within funding agencies, GRUAN endorsement of the quality of a site’s measurement programmes is expected to support resourcing for GRUAN sites. Through GRUAN’s governing bodies, sites shall have access to the support and service structures provided by the AOPC (Atmospheric Observation Panel for Climate), the WCRP (World Climate Research Programme), UNEP (United Nations Environment Programme), IOC (Intergovernmental Oceanographic Commission) of the United Nations Educational, Scientific and Cultural Organization (UNESCO), ICSU (International Council for Science) and WMO (World Meteorological Organization). In addition to requiring long‐term homogeneity of measurement programmes at sites within the network, GRUAN has a strong emphasis on network‐wide homogeneity of measurement time series. Measurements at GRUAN sites shall be anchored to a reference that provides traceability to internationally recognized measurement standards. GRUAN has established a number of task teams to entrain skills and expertise from across the international community in measurement sciences. Sites joining GRUAN shall have access to this pool of expertise. GRUAN has developed and implemented a state‐of‐the‐ art data delivery service through the National Climate Data Center of NOAA. Raw measurements made at GRUAN sites shall be processed and quality assured at a centralised data processing facility and provided to a wide range of data users.

The primary goals of GRUAN are to provide vertical profiles of reference measurements suitable for reliably detecting changes in global and regional climate on decadal time scales, initially for temperature, pressure and water vapour, with the aim of expanding to other essential climate variables (ECVs), as resources permit, in liaison with other existing scientific networks. The measurements will provide a calibrated reference standard for global satellite‐based measurements of atmospheric ECVs, will ensure that potential gaps in satellite measurement programmes do not jeopardize the long‐term climate record, will be a reference standard for the measurements made within the existing GCOS Upper‐Air network, and will provide data to fully characterize the properties of the atmospheric column.These goals have been jointly endorsed by GCOS and WMO.

The Manual recognizes that GRUAN is a heterogeneous network that includes sites from both the research community and the operational meteorological community. The mandatory practices required of GRUAN sites, as detailed in this Manual, reflect GRUAN’s primary goal of providing reference quality observations of the atmospheric column while accommodating the diverse capabilities of sites within the network. However, WG‐GRUAN certification of measurement programmes at a GRUAN site goes beyond considering the extent to which the site adheres to the mandatory practices outlined in this Manual and considers the added value that the site brings to the network. The assessment of the added value is an expert judgement.

The Manual is augmented by a more detailed GRUANGuide to Operations(GCOS‐171) which provides guidelines on how the protocols detailed in this Manual might be achieved, and by a series of technical documents available from the GRUAN web site at Since GRUAN is a WIGOS (WMO Integrated Global Observing System) Implementation Project, relevant information from this Manual and the Guide is expected to be incorporated into the WMO regulatory material, especially the WIGOS Manual and the WMO Manual on the Global Observing System (WMO‐No. 544) and the Guide on the Global Observing System (WMO‐No. 488) 1 . GRUAN observing systems and operating practices, as detailed in technical documents associated with each observing technique available in GRUAN, are expected to be referred to in the WMO Guide to Instruments and Methods of Observation (WMO‐No.8) and the GRUAN Guide and Manual. A GRUAN site may be a scientific observing site outside of the WMO operational Global Observing System, but the long‐term observational procedures are expected to follow the guidelines laid down in this GRUAN Manual, and in the GRUANGuide to Operations, whether it is primarily a scientific site or whether it is already part of the Global Observing System. The WMO Manuals are expected to reference these GRUAN practices.