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SYNOP data are first subjected to an automatic quality control where we check for missing values and if the values are within certain physical limits. This automatic QC is followed by a manual QC performed by RMI staff members.

Different instruments are calibrated by RMI in its calibration laboratory.

The TEMPERATURE sensors are calibrated by comparing the pt100 sensor of the station with the pt25 reference sensor of the calibration lab (which are calibrated by the national metrology lab). They are compared in a thermostatic bath which contains an “azeotropic mixture of propyleenglycol and water” (50-50%). This allows the same bath and mixture to be used for the entire temperature range (-25°C to 35°C). The calibration is performed at 6 fixed temperatures: -25°C, -10°C, 0°C, 10°C, 20°C and 35°C.

The calibration of the PRESSURE sensors is performed using a balance system with two pumps (for under and over pressure) and three reference sensors: a recent one (rpm4) and two older ones (paroscientific) in an automated way with 3 up and down cycles within the pressure range 810-1050hPa, with a calibration every 30hPa.

The calibration of the HUMIDITY sensors is performed in a climate closet (Weiss) by varying the temperature and relative humidity and by using a chilled mirror sensor.