Open AccessNMHCs and halocarbons in Asian continental outflow during the Transport and Chemical Evolution over the Pacific (TRACE‐P) Field Campaign: Comparison With PEM‐West B
Author(s) -
Blake Nicola J.,
Blake Donald R.,
Simpson Isobel J.,
Meinardi Simone,
Swanson Aaron L.,
Lopez Jimena P.,
Katzenstein Aaron S.,
Barletta Barbara,
Shirai Tomoko,
Atlas Elliot,
Sachse Glen,
Avery Melody,
Vay Stephanie,
Fuelberg Henry E.,
Kiley Christopher M.,
Kita Kazuyuki,
Rowland F. Sherwood
Publication year - 2003
Publication title -
journal of geophysical research: atmospheres
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.67
H-Index - 298
eISSN - 2156-2202
pISSN - 0148-0227
DOI - 10.1029/2002jd003367
Subject(s) - outflow , environmental science , trace gas , mixing ratio , tracer , atmospheric sciences , climatology , oceanography , geology , physics , nuclear physics
We present an overview of the spatial distributions of nonmethane hydrocarbons (NMHCs) and halocarbons observed over the western north Pacific as part of the NASA GTE Transport and Chemical Evolution over the Pacific (TRACE‐P) airborne field campaign (February–April 2001). The TRACE‐P data are compared with earlier measurements from the Pacific Rim during the Pacific Exploratory Mission‐West B (PEM‐West B), which took place in February–March 1994, and with emission inventory data for 2000. Despite the limited spatial and temporal data coverage inherent to airborne sampling, mean levels of the longer‐lived NMHCs (including ethane, ethyne, and benzene) were remarkably similar to our results during the PEM‐West B campaign. By comparison, mixing ratios of the fire extinguisher Halon‐1211 (CF 2 ClBr) increased by about 50% in the period between 1994 and 2001. Southern China (south of 35°N), and particularly the Shanghai region, appears to have been a substantial source of Halon‐1211 during TRACE‐P. Our previous analysis of the PEM‐West B data employed methyl chloroform (CH 3 CCl 3 ) as a useful industrial tracer. However, regulations have reduced its emissions to the extent that its mixing ratio during TRACE‐P was only one‐third of that measured in 1994. Methyl chloroform mixing ratio “hot spots,” indicating regions downwind of continuing emissions, included outflow from the vicinity of Shanghai, China, but particularly high emission ratios relative to CO were observed close to Japan and Korea. Tetrachloroethene (C 2 Cl 4 ) levels have also decreased significantly, especially north of 25°N, but this gas still remains a useful indicator of northern industrial emissions. Methyl bromide (CH 3 Br) levels were systematically 1–2 pptv lower from 1994 to 2001, in accord with recent reports. However, air masses that had been advected over Japan and/or South Korean port cities typically exhibited elevated levels of CH 3 Br. As a consequence, emissions of CH 3 Br from Japan and Korea calculated employing CH 3 Br/CO ratios and scaled to CO emission inventory estimates, were almost as large as for all of south China (south of 35°N). Total east Asian emissions of CH 3 Br and CH 3 Cl were estimated to be roughly 4.7 Gg/yr and 167 Gg/yr, respectively, in 2001.