A comparison of very short-lived halocarbon (VSLS) and DMS aircraft measurements in the Tropical West Pacific from CAST, ATTREX and CONTRAST

Abstract

Abstract. We present a comparison of aircraft measurements of halogenated very short-lived substances (VSLS) and dimethyl sulphide (DMS, C2H6S) from a co-ordinated campaign in Jan/Feb 2014 in the Tropical West Pacific. Measurements were made on the NASA Global Hawk, NCAR GV HIAPER and FAAM BAe146 using four separate GC-MS instruments operated by the University of Miami (UoM), the National Centre for Atmospheric Research (NCAR) and two from the University of York (UoY), respectively. The instruments were inter-calibrated during the campaign period using two gas standards on separate scales; a NOAA SX-3581 standard representative of clean low-hydrocarbon air, and an Essex canister prepared by UoM representative of coastal air, which was higher in VSLS and hydrocarbon content. UoY and NCAR use the NOAA scale/standard for VSLS calibration and UoM use a scale based on dilutions of primary standards calibrated by GC with FID and AED (atomic emission) detection. Analysis of the NOAA SX-3581 standard resulted in good agreement for CH2Cl2, CHCl3, CHBr3, CH2Br2, CH2BrCl, CHBrCl2, CHBr2Cl, CH3I CH2ICl and CH2I2 (average RSD