Quality Assurance (QA)
The GAW quality assurance (QA) system impacts all aspects of atmospheric chemistry observations, including
• training of station personnel;
• assessment of infrastructures, operations and the quality of observations at the sites;
• documentation of data submitted to the WDCs;
• improvement of the quality and documentation of legacy data at the WDCs.
The primary objectives of the GAW QA system are to ensure that the data in the World Data Centres (WDCs) are consistent, of known and adequate quality, supported by comprehensive metadata, and sufficiently complete to describe global atmospheric states with respect to spatial and temporal distribution.
Conceptual framework of the GAW quality system
(click to enlarge)
Five types of Central Facilities dedicated to six groups of measurement variables are operated by WMO Members and form the basis of quality assurance and data archiving for the GAW global monitoring networks. They include Central Calibration Laboratories (CCLs) that host primary standards (PS), Quality Assurance/Science Activity Centres (QA/SACs), World Calibration Centres (WCCs), Regional Calibration Centres (RCCs), and World Data Centres (WDCs) with responsibility for archiving and access to GAW data.
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.
The principles of the GAW QA system
|Full support of the GCOS Climate Monitoring Principles|
|Network-wide use of only one reference standard or scale (primary standard). In consequence, there is only one institution that is responsible for this standard.|
|Full traceability to the primary standard of all measurements made by Global, Regional and Contributing GAW stations.|
|The definition of data quality objectives (DQOs).|
|Establishment of guidelines on how to meet these quality targets, i.e., harmonized measurement techniques based on Measurement Guidelines (MGs) and Standard Operating Procedures (SOPs).|
|Establishment of MGs or SOPs for these measurements.|
|Use of detailed log books for each parameter containing comprehensive meta information related to the measurements, maintenance, and 'internal' calibrations.|
|Regular independent assessments (system and performance audits).|
|Timely submission of data and associated metadata to the responsible World Data Centre as a means of permitting independent review of data by a wider community.|