One of the first tasks of the GCOS programme was to define a subset of the World Weather Watch (WWW)<ref>{{cite news |title= World Weather Watch |publisher=WMO |year= 2013 |url= http://www.wmo.int/pages/prog/www|accessdate= 2013-11-05}}</ref> stations appropriate for basic climate monitoring. The subset of roughly 1000 baseline surface stations became the GCOS Surface Network (GSN),<ref>{{cite news |title= GCOS Observations and Systems |publisher=GCOS |year= 2013 |url= http://www.wmo.int/pages/prog/gcos/index.php?name=ObservingSystemsandData|accessdate= 2013-11-05}}</ref> while a subset of 150 upper air stations was designated as the GCOS Upper-Air Network (GUAN).<ref>{{cite news |title= The GCOS Upper-Air Network - GUAN |publisher=GCOS/GOSIC |year= 2013 |url= http://gosic.org/content/gcos-upper-air-network-guan-program-overview|accessdate= 2013-11-05}}</ref> These were built on existing WMO classifications and became the initial baseline components of the atmospheric networks. Considerations for selection of GSN included spatial distribution, length and quality of record, long-term commitment, and degree of urbanization. Similar considerations were used for GUAN. Designation of these networks benefited both the GCOS and the National Meteorological and Hydrological Services (NMHS). For NMHSs, designation of a station as part of the global climate network helped sustain support for these sites with long-term records. The networks provided the foundation for the Regional Basic Climatological Network,<ref>{{cite news |title= Regional Basic Climatological Network |publisher=WMO |year= 2013 |url= http://www.wmo.int/pages/prog/www/ois/rbsn-rbcn/rbsn-rbcn-home.htm|accessdate= 2013-11-05}}</ref> which provides far greater spatial detail on the variability of climate. | One of the first tasks of the GCOS programme was to define a subset of the World Weather Watch (WWW)<ref>{{cite news |title= World Weather Watch |publisher=WMO |year= 2013 |url= http://www.wmo.int/pages/prog/www|accessdate= 2013-11-05}}</ref> stations appropriate for basic climate monitoring. The subset of roughly 1000 baseline surface stations became the GCOS Surface Network (GSN),<ref>{{cite news |title= GCOS Observations and Systems |publisher=GCOS |year= 2013 |url= http://www.wmo.int/pages/prog/gcos/index.php?name=ObservingSystemsandData|accessdate= 2013-11-05}}</ref> while a subset of 150 upper air stations was designated as the GCOS Upper-Air Network (GUAN).<ref>{{cite news |title= The GCOS Upper-Air Network - GUAN |publisher=GCOS/GOSIC |year= 2013 |url= http://gosic.org/content/gcos-upper-air-network-guan-program-overview|accessdate= 2013-11-05}}</ref> These were built on existing WMO classifications and became the initial baseline components of the atmospheric networks. Considerations for selection of GSN included spatial distribution, length and quality of record, long-term commitment, and degree of urbanization. Similar considerations were used for GUAN. Designation of these networks benefited both the GCOS and the National Meteorological and Hydrological Services (NMHS). For NMHSs, designation of a station as part of the global climate network helped sustain support for these sites with long-term records. The networks provided the foundation for the Regional Basic Climatological Network,<ref>{{cite news |title= Regional Basic Climatological Network |publisher=WMO |year= 2013 |url= http://www.wmo.int/pages/prog/www/ois/rbsn-rbcn/rbsn-rbcn-home.htm|accessdate= 2013-11-05}}</ref> which provides far greater spatial detail on the variability of climate. |