GCOS Implementation Plan - WMO

Implementation Plan for the Global Observing System for Climate in Support of the UNFCCC
(2010 Update)
Figure 5: Frequency of receipt of temperature data from GUAN radiosondes reaching the
stratospheric level of 10 hPa at GUAN Monitoring Centre 1994-2008 (Source: ECMWF).
A continuing international effort is underway involving the WMO CBS, WMO CIMO and GCOS to help
alleviate the negative impact of the high cost of radiosondes and obsolescent equipment on network
performance. These groups are encouraged to continue their activities to promote testing of
instruments and tracking equipment, technology improvements, capacity-building and policy actions
to ensure that affordable high-quality sondes are readily available for global climate monitoring.
The GCOS Steering Committee has designated a subset of the WWW/GOS radiosonde network as
the baseline GUAN. GUAN currently consists of 164 radiosonde stations fairly evenly distributed over
the globe. Figure 5 gives an indication of the increase in GUAN performance over the past years. The
AOPC works with the WMO CBS, the WMO RAs and the NMSs to implement a programme for the
sustained operation of GUAN, together with its associated infrastructure. For some individual stations,
technical cooperation is necessary from other nations or agencies and/or the GCOS Cooperation
Mechanism, to equip the stations, provide training of operators and in some instances to support
continuing operations by Parties in need (e.g., provision of expendables).
Action A15 [IP-04 A15]
Action: Improve operation of the GUAN, including infrastructure and data management.
Who: Parties operating GUAN stations, in cooperation with GCOS Secretariat and WMO CBS.
Time-Frame: Ongoing.
Performance Indicator: Percentage of data archived in WDC Asheville.
Annual Cost Implications: 10-30M US$ (80% in non-Annex-I Parties).
Outstanding issues concerning the quality of radiosonde measurements for climate monitoring and
change-detection purposes have led to a proposal for a GCOS Reference Upper Air Network
(GRUAN) of about 40 sites routinely deploying high-quality radiosondes and making other groundbased
measurements such as from ozone sondes, GPS delay and lidars. In addition to making a vital
direct contribution to climate monitoring across all climate zones, this network will be extensively used
to calibrate and validate various satellite observations and is expected also to provide new information
on humidity in the upper troposphere and lower stratosphere needed to understand better the role of
water vapour in the radiation budget.
GRUAN planning was initiated at workshops held in 2006 and 2007 and further elaborated under the
auspices of the AOPC Working Group on Atmospheric Reference Observations (WG ARO) by setting
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