Greenhouse gas measurement capability at the Carbon Related Atmospheric Measurement (CRAM) Laboratory at the University of East Anglia, United Kingdom

Abstract The new Carbon Related Atmospheric Measurement (CRAM) Laboratory, School of Environmental Sciences, University of East Anglia (UEA), United Kingdom has been equipped to make highly precise and accurate atmospheric measurements of O2, CO2, CH4, CO, N2O, SF6, and Ar/N2. The measurement system operates as a single contiguous unit, with sample air passing consecutively through four analysers. A bespoke software program controls the system and collects all data. The measurement system is designed to accommodate analyses of air from high pressure cylinders or low pressure flasks, as well as direct monitoring of outside air from inlets installed on the roof. We incorporated flexibility in our design to allow sample analyses from a wide range of flask types from our collaborators, with the only stipulation being a necessity for two valves at one end of the flask. The system is fully automated and was designed with the objectives to minimise time, labour and logistical costs, and calibration standard consumption. All analysers are routinely calibrated against a suite of 14 primary calibration standards from NOAA/ESRL and Scripps Institution of Oceanography. To support the CRAM Laboratory and our field station operations, we have also built a high pressure Cylinder Filling Facility (CFF) for preparing our own secondary calibration and working standards. Cylinders are filled with dry air to a pressure of up to 300 bar and with a dewpoint less than 1 ppm H2O. In addition, the CFF has the capability to produce a wide range of below or above ambient concentrations for all gas species listed above. We have also designed a new style of glass sampling flask. Our flask has two valves at one end which seal with PCTFE seats, one of which has a diptube extending to near the bottom of the flask. Connections are via ball and cup joints with a pinch clamp. The flask internal volume is 2.4 L and it has dimensions such that it can be used with the ‘standard’ NOAA shipping box, or our own cardboard boxes that hold six flasks.