The Global Atmosphere Watch (GAW) Programme of the World Meteorological Organization (WMO) is the only existing long-term international global programme that coordinates observations and analysis of atmospheric composition changes. The GAW Programme is a collaboration of more than 100 countries and it relies fundamentally on the contributions of these WMO member states to help to build a single, coordinated global understanding of atmospheric composition and its change. The mission of GAW is implemented through "maintaining and applying global, long-term observations of the chemical composition and selected physical characteristics of the atmosphere; emphasizing quality assurance and quality control; delivering integrated products and services of relevance to users". Ozone vertical profiles, with a focus on the stratosphere and upper troposphere, are included in the set of key variables for GAW.

The primary objectives of the GAW Quality Assurance (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. In short, the GAW QA system relies on (i) Central Calibration Laboratories (CCLs) that host the primary standard of an entire network, (ii) World and/or Regional Calibration Centres (WCCs, RCCs) that should link observations at GAW stations to these world reference primary standards and ensure network comparability/compatibility through intercomparison campaigns and regular audits, and (iii) Quality Assurance Science Activity Centres (QA/SACs), responsible for the development and implementation of the quality assurance system in the GAW programme for specific atmospheric parameters.

The RMI is recognized by the WMO as the Quality Assurance/Science Activity Centre for Ozonesondes (QA/SAC) for the WMO/GAW Programme. Forschungszentrum Jülich (FZJ) hosts the World Calibration Centre for Ozonesondes (WCCOS) with the Central Calibration Laboratory (CCL) for ozonesondes, existing of (i) the environmental simulation chamber to simulate ozone balloon soundings and (ii) the ozone reference standard (UV-photometer) for the entire ozonesonde network (see figure on the left below). The RMI and the FZJ have signed a Memoradum of Understanding (MoU) to cooperate for conducting Jülich Ozonesonde Intercomparison Experiments (JOSIE) at Jülich.

In its role as QA/SAC for ozonesondes, the RMI will perform the following activities:

1. organize, in close collaboration with FZJ, JOSIE campaigns in the simulation chamber in Jülich. Following the MoU between FZJ and RMI, RMI will be responsible for the scientific organization of JOSIE, which includes the preparation, operation of JOSIE, and the scientific analysis and evaluation of the results before, during, and after a JOSIE campaign. RMI will be also responsible for the logistics and organization to conduct a JOSIE campaign, for organizing and providing the ozonesondes and their supplies necessary to be used in JOSIE.
2. contribute to the development of quality control procedures like measurement guidelines (MG) and standard operating procedures (SOP), see cover on the right figure here above, as required in collaboration with the relevant groups within the GAW Programme. RMI will foster a harmonization of quality assurance procedures within the GAW Expert Team on Atmospheric Composition Measurement Quality.
3. help GAW stations to implement the standard operating procedures and quality control procedures at their sites and archive their (meta)data in the international databases like World Ozone and UV Data Centre (WOUDC).
4. promote the scientific use of the GAW ozonesonde data, and encourage and participate in scientific collaboration with ozonesonde experts and data users; (re)present the ozonesonde data and ongoing activities at scientific meetings, workshops, and symposia.
5. provide training, technical help, and workshops to GAW stations.
6. foster the development of the WMO/GAW observational network through the promotion of new observational sites in regions such as Africa, Asia and South America, in close collaboration with other partners like NASA and NOAA.
7. make public its involvement in the WMO/GAW Programme (e.g. on its website, newsletters, etc.) and report on their WMO/GAW related activities to WMO.

Roeland Van Malderen
Royal Meteorological Institute
Ringlaan 3,
B-1180 Brussels, Belgium