The C3S project 'Access to Observations for Baseline And Reference Observation Networks (BARON)', referred as 'C3S_311a_Lot3', aims at rationalising, harmonising and improving access to atmospheric observations and data products provided by a large variety of existing networks, in order to facilitate climate monitoring, to estimate ECVs and uncertainty assessments, and to maximize the number of users of the existing in-situ observatiog capabilities.

The subset of ECVs selected for C3S_311a_Lot3 includes surface temperature, atmospheric temperature and humidity (vertical profiles), O₃ (column and profiling concentration), wind profiles (from radiosoundings), CO, CO₂ and CH₄ (column concentrations), and water vapour content (columnar from GPS/GNSS only). For these ECVs demonstrable Baseline and Reference quality measurement networks are assured.The list of networks targeted in the project include GRUAN, GUAN, USCRN, RBSN, NDACC, EuBrewNet, PGN, ICOS, TCCON, EUREF, IGS and a number of other WMO networks like GAW/WOUDC.

The present web page gives access to the NDACC data QC reports. This NDACC QC service builds upon the QC service developed in the CAMS-27 contract.The CAMS-27 contract main objective is to support selected observation sites to provide their quality measurement data more rapidly to NDACC so that it becomes available for CAMS model validation. CAMS-27 only accepts data submitted to NDACC in the latest GEOMS data format and satisfying the necessary quality requirements for use in model validation.

The NDACC instrument types and associated data products that are eligible for the present QC support are the following:

The international Network for the Detection of Atmospheric Composition Change (NDACC) has the objective to provide a consistent andstandardised set of long-term measurements of atmospheric trace gases, particles, and physical parameters via a suite of globally distributed research and observation sites. Officially operational since 1991, NDACC was established during the late 1980s in response to the need to document and understand worldwide stratospheric perturbations resulting from increased anthropogenic emissions into the atmosphere of long- lived halogenated source gases with strong ozone-depleting and global-warming potentials.

The NDACC is an international activity, it has been endorsed by the United Nations Environment Programme (UNEP) and the International Ozone Commission (IO3C) of the International Association of Meteorology and Atmospheric Sciences (IAMAS). It has also been recognised by the World Meteorological Organisation.

According to the NDACC data  protocol, measurement data becomes publicly available not later than one year after the measurement.