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The primary objective of the GAW Quality Assurance (QA) system is to ensure that the data deposited in the World Data Centres (WDCs) are consistent, meet the GAW data quality objectives and are supported by comprehensive description of methodology. The QA system involves Quality Assurance/Science Activity Centres (QA/SACs) and Calibration Centres that ensures the quality of observations through adherence to measurement guidelines established by the Scientific Advisory Groups and through calibrations that are traceable to World Calibration Standards.  Ideally, QA/SACs should have global responsibility for specific atmospheric parameters. In practice, this is generally the case but, occasionally, responsibility for QA/SAC with a more regional scope is assumed by a WMO member. 


Long-term education, training, workshops, calibrations station audits/visits and twinning are also provided to build capacities in atmospheric sciences in the GAW network.  These Capacity building activities are of increased importance as many GAW stations in developing countries have become operational.

GAW QA procedures address the quality of an observation through maintenance of components of the entire measurement process, from operational procedures at stations to submission of properly quality controlled data to a World Data Centre.  The recommended basic GAW QA principle (WMO/GAW Strategy of Implementation, 2001 Report No.142 ) are:

  • to use internationally accepted methods and vocabulary to describe uncertainty in measurements (ISO standards);

  • to harmonise measurement methodology at all stations using measurement guidelines and standard operating procedures (SOPs);

  • to conduct regular performance and system audits to check the conformity of a station with principles of the GAW QA system.

In addition, parameter-specific measurement principles are: 

  • use data quality objectives (DQOs) specifying tolerable levels of uncertainty, as well as completness, comparability and representativeness;

  • define one network-wide reference standard or scale where applicable;

  • maintain full traceability to the reference standard for all measurements made by GAW Global and Regional stations;

  • establish SOPs for the measurements;

  • maintain a detailed "log book" documentation of measurement methodology and procedures on instruments, maintenance, and "internal" calibration. 




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