GCOS Upper Air Network (GUAN)
IntroductionThe Global Climate Observing System (GCOS) was established in 1992 to ensure that the observations and information needed to address climate-related issues are taken and made available to all potential users. It is co-sponsored by the World Meteorological Organization (WMO), the Intergovernmental Oceanographic Commission (IOC) of UNESCO, the United Nations Environment Programme (UNEP) and the International Council for Science (ICSU).
GCOS does not directly make observations nor generate data products. Rather, its role is to stimulate, encourage, coordinate or otherwise facilitate making necessary observations by national or international organizations in support of their own requirements and other shared goals. GCOS provides an operational framework for integrating, and enhancing as needed, the observational systems of participating countries and organizations into a comprehensive system focused on requirements for climate studies. To do this, GCOS builds upon existing and developing observing systems such as the Global Ocean Observing System, the Global Terrestrial Observing System, and the Global Observing System and Global Atmospheric Watch of the World Meteorological Organization. The GCOS Upper air Network, or GUAN, is one of the GCOS atmospheric networks.
The principal aims of the GUAN include ensuring a relatively homogeneous distribution of upper air stations that meet specific record length and observation continuity requirements as outlined by GCOS, and to make available current and historical upper air data for climate research. To meet these aims, GCOS Monitoring, Analysis, Archive and Lead Centres have been established for the GUAN. The WMO and GCOS act on information provided by the GUAN Monitoring, Analysis and Lead Centres to feedback to contributing members to enhance network performance and encourage the provision of station data from the GUAN.
The Met Office, Hadley Centre of the UK, routinely monitor and quality control monthly CLIMAT TEMP radiosonde data and develop upper air datasets for use in climate research. The European Centre for Medium Range Weather Forecasts monitor the receipt and quality of daily TEMP data. The National Oceanic and Atmospheric Administration (NOAA) National Climatic Data Center (NCDC) update and quality control daily upper air data and historical metadata as part of this Health of the Networks project, and in support of the Integrated Global Radiosonde Archive. The World Data Center for Meteorology (WDC) holds the GUAN data archive.
Performance IndicatorsData Completeness
Completeness is computed as the percentage of reported observations at each mandatory level relative to the total number of possible sounding days in each data month. The 00 and 12 UTC standard reporting times are summarized separately. Soundings taken within 2 hours of the nominal reporting times are counted. Separate calculations are provided for each sounding parameter: geopotential height; temperature; dew point depression; wind speed; and wind direction. In addition, percent completeness is provided relative to those cases when all parameters were available at a given mandatory level as well as for cases where at least one parameter was available.
Data Availability and Source
For a variety of reasons, including differences in decoding practices, some messages transmitted over the GTS are decoded only at certain receiving centers and not at others. Thus, even though extensive duplication generally exists among the core, Australian, and Russian GTS data, the latter two sources occasionally supply soundings that are either not present or incomplete in the core data. Recent GUAN and IGRA data come only from GTS data decoded at NCDC.
GUAN Station Metadata
Metadata for GUAN sites is available from the Integrated Global Radiosonde Archive (IGRA) website at: IGRA Metadata.
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