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Medusa-GCMS

AGAGE calibration scales are used for all species measured in the network with the exception of CO2 and CH4. A standard calibration tank is measured alternately to each air measurement.

Calibration of the Medusa is controlled by a central calibration centre at Scripps Institute of Oceanography (SIO). Tanks of air (J-tanks) are filled here and calibrated against the gold standards here to assign concentration numbers to the range of species measured. These J-tanks are then sent out to the stations and used to calibrate measurements of Medusa species. J-tank standards are sent back to SIO once almost empty and re-measured to ensure no drift, loss or growth of any species has occurred within the tank whilst on site. In this way any drift can be monitored and corrected for. J-tanks are measured weekly against the H-tanks (air filled at Mace Head). These H-tanks are measured in every second run to ensure accurate calibration of all species. This method also means that the J-tanks last for up to 1 year rather whereas the H-tanks last for approximately 13 weeks.

Calibration

Medusa calibration Schematic of the procedure carried out for calibration of all Medusa trace gas species.

GasAGAGE scaleGasAGAGE scale
CF4SIO-05CFC-11SIO-05
C2F6 (PFC-116)SIO-07CFC-12SIO-05
C3F8 (PFC-218)SIO-07CFC-13SIO-UB-p
c-C4F8SIO-10-pCFC-113SIO-05
HFC-23 (CHF3)SIO-07CFC-114SIO-05
HFC-32SIO-07CFC-115SIO-05
HFC-134aSIO-05H-1211SIO-05
HFC-152aSIO-05H-1301SIO-05
HFC-125UB-98H-2402NOAA-1992-p
HFC-143aSIO-07CH3ClSIO-05
HFC-227eaEmpa-2005CH3BrSIO-05
HFC-236faEmpa-2009-pCH3INOAA-Dec09
HFC-43-10meeSIO-10-pCH2Cl2UB-98
HFC-365mfcEmpa-2003CH2Br2NOAA-Jul10-p
HFC-245faEmpa-2005CHCl3SIO-98
HCFC-22SIO-05CHBr3NOAA-Dec09-p
HCFC-141bSIO-05CCl4SIO-05
HCFC-142bSIO-05CH3CCl3SIO-05
HCFC-124NOAA-2003BCHCl=CCl2 (TCE)UB-98
CFC-11SIO-05CCl2=CCl2 (PCE)NOAA-2003B
Last Updated: 5 October 2012