CO2 measurements by means of flasks (about every two weeks) from April 1989 to December 1997. Continuous measurements of the CO2 since March 1993. Half an hour averages are available up to December 2007. Since 2008 the minimum temporal resolution for the mean values is based on hourly averages.

Since 1993, ULTRAMAT 5E NDIR Analyser, SIEMENS.

Since 2008 it is also working an ULTRAMAT 6E NDIR Analyser, SIEMENS.

The atmospheric CO2 concentration is measured by means of a non dispersive infrared analyser (ULTRAMAT 5E and, recently, 6E) working, respectively, in the range 350-400 ppmv (5E) and 360-410 ppmv (6E). The uncertainty of the measurement is about 0.07 ppmv.

The CO2 dataset of the Plateau Rosa is composed by two partially overlapped series: the first one contains weekly data measured using flasks and extends from April 1989 to December 1997; the second one contains continuous measurements, and reports data since March 1993.

The atmospheric CO2 concentration is measured by means of two non dispersive infrared analysers (ULTRAMAT 5E and, recently, 6E) working, respectively, in the range 350-400 ppmv (5E) and 360-410 ppmv (6E). The CO2 measurements are referred to the WMO X2007 international mole fraction scale.

The water content in the air sampling (flasks and continuous measurements) is eliminated by means of a cryogenic cooler working at -65°C.

The uncertainty of the measurement is about 0.07 ppmv.

Scale and Calibration (traceability): WMO X93 scale up to 2007, now WMO X2007 scale.

Measurement Calibration: The CO2 analyser of Plateau Rosa is calibrated with the NOAA-CMDL primary standards. Moreover the secondary and tertiary standards (the so-called "working standard") are acquired by SIAD and referred to the primary standard. Usually the comparison among the primary and the secondary/tertiary standard is performed every six months or, at the maximum, every year. The analyzer calibration test is realized respectively every 3 days with the secondary standard and every 6 hours with the working standard.

Flag: "0" means "background data" (values identified as background data by means of our criteria of selection); "1" means "not background data" (for example, due to large variability of CO2 concentration within a half an hour or values identified as not background data by means of our criteria of selection); "2" means "invalid data" (for example, instrumental problems due to the missed electrical power, incorrect calibration measurements, sampling flow incorrect and so on).