In Situ Measurements of Long-Lived Trace Gases in the Lower Stratosphere by Gas Chromatography

摘要

Detailed information on the four-channel Airborne Chromatograph for Atmospheric Trace Species (ACATS- IV), used to measure long-lived atmospheric trace gases, is presented. Since ACATS-IV was last described in The literature the temporal resolution of some measurements was tripled during 1997-99, chromoatography was Significantly changed, and data processing improved. ACATS-IV presently measures CCl_3F [chlorofluorocarbon (CFC)-11], CCl_2FCClF_2 (CFC-113), CH_3CCl_3 (methyl chloroform), CCl_4 (carbon tetrachloride), CH_4 (methane), H_2 (hydrogen), and CHCl_3(chloroform) every 140 s,a nd N_2O (nitrous oxide), CCl_2F_2 (CFC-12), CBrClF_2 (halon- 1211), and SF_6 (sulfur hexafluoride) every 70 s. An in-depth description of the instrument operation, standard- ization, calibration, and data processing is provided, along with a discussion of precision and uncertainties of ambient air measurements for several airborne missions.