GCOS Reference Upper-Air Network ()

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Figure 4: GRUAN Stations as of 2014

The GCOS (Global Climate Observing System) Reference Upper-Air Network (GRUAN) is an international reference-observing network, designed fill an important gap in the current global observing system. GRUAN measurements provide long-term, high-quality climate data records from the surface, through the troposphere, and into the stratosphere. These are 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.

Target requirements for accuracy, stability, and vertical resolution have been defined for a range of essential climate variables, as well as the necessary measurement regimens required to meet the needs of intended users of GRUAN data. The Working Group on GRUAN, which meets annually at implementation and coordination meetings, provides oversight of GRUAN. A periodically reviewed implementation plan guides the activities of the Working Group. Operational support is provided through the GRUAN Lead Centre, hosted at the Meteorological Observatory at Lindenberg (Germany), supported by the National Meteorological Service, Deutscher Wetterdienst. Task teams on radiosondes, GNSS precipitable water, measurement schedules and associated site requirements, ancillary measurements, and site representation further support the Working Group and Lead Centre. Formal GRUAN operating procedures, including formal site assessment and certification, are documented in the GRUAN Manual and Guide.

The first GRUAN data product (the RS92 radiosonde data product) is available to users via NOAA/NCDC. An initial set of candidate GRUAN sites has been identified, and some sites already have had their RS92 radiosonde programs GRUAN certified. GRUAN is envisaged as a III-8 global network of eventually 30 to 40 sites that, to the extent possible, builds on existing observational networks and capabilities, including those of NDACC. Criteria to guide the expansion and design of GRUAN have been developed through a dedicated network design workshop to ensure that the Network evolves in a way to meet the goals of GRUAN. The report from this workshop can be obtained at http://www.dwd.de/EN/research/international_programme/gruan/download/gru...