Environnement 41M up to June 2011. Starting from July 2011 by means of THERMO 49i with internal calibrator. Range of measurement: 0 – 500 ppbv. Scale and Calibration (traceability):RSE have an internal metrological lab in Milan headquarters. The primary calibrator is a Thermo Electron 49PS, calibrated by Primary Italian Metrological Institute INRIM. The analysers are periodically verified in respect of the calibrator in the scale 0-100ppbv. The procedure is agree on the ISO 9169:2006 standard. Measurement Calibration: The instrument is calibrated (up to June 2011) by means of an external ozone source (primary calibrator) when the personal is operative in situ (at least every twice months). Since July 2011 we use a THERMO 49i with internal calibration Flag: "1" means "valid data". The data is considered correct but no criteria, at the moment, has been applied to identify the background data; "2" means "invalid data" (for example, instrumental problems due to the missed electrical power, incorrect calibration measurements, sampling flow incorrect and so on).

The monitoring station of Plateau Rosa is situated in the Western Italian Alps (3480m asl). It belongs to the National Institute for Astrophysics (INAF)-Institute of Interplanetary Space Physics (IFSI), Turin Section. The measurement programme of the CO2 has been run by CESI RICERCA since April 1989 (at beginning by means of biweekly samplings until December 1997 and then by means of continuous measurements since April 1993). The atmospheric CO2 concentration is measured by means of a non-dispersive infrared analyser (ULTRAMAT 5E and, in these last years, ULTRAMAT 6E). The CO2 measurements are referred to the WMO X2007 international mole fraction scale. The CO2 atmospheric concentration is expressed in ppmv in dry air. The measurement programme of the CH4 has been run by CESI RICERCA since February 1991 (at beginning by means of biweekly samplings until December 2002 and then by means of continuous measurements since January 2002). The CH4 atmospheric concentration is expressed in ppbv and the measured method is gas chromatography by using a FID (NIRA Mod. Venus). The surface ozone measurements (O3) is available since 1989 but only in these last years have been included in a specific internal protocol and submitted to WDCGG. The ozone atmospheric concentration is expressed in ppbv and the measured method is the UV light absorption analysis by using a Environnement 41M, and recently, a Thermo 49