Chemical isolation in the Asian monsoon anticyclone observed in Atmospheric Chemistry Experiment (ACE-FTS) data M. Park1, W. J. Randel1, L. K. Emmons1, P. F. Bernath2,3, K. A. Walker2,*, and C. D. Boone2 1National Center for Atmospheric Research, Boulder, Colorado, USA 2Department of Chemistry, University of Waterloo, Waterloo, Ontario, Canada 3Department of Chemistry, University of York, Heslington, York, UK *now at: Department of Physics, University of Toronto, Toronto, Ontario, Canada
Abstract. Evidence of chemical isolation in the Asian monsoon anticyclone is presented
using chemical constituents obtained from the Atmospheric Chemistry
Experiment Fourier Transform Spectrometer instrument during summer
(June–August) of 2004–2006. Carbon monoxide (CO) shows a broad maximum over
the monsoon anticyclone region in the upper troposphere and lower
stratosphere (UTLS); these enhanced CO values are associated with air
pollution transported upward by convection, and confined by the strong
anticyclonic circulation. Profiles inside the anticyclone show enhancement
of tropospheric tracers CO, HCN, C2H6, and C2H2 between
~12 to 20 km, with maxima near 13–15 km. Strong correlations are
observed among constituents, consistent with sources from near-surface
pollution and biomass burning. Stratospheric tracers (O3, HNO3 and
HCl) exhibit decreased values inside the anticyclone between ~12–20 km.
These observations are further evidence of transport of lower
tropospheric air into the UTLS region, and isolation of air within the
anticyclone. The relative enhancements of tropospheric species inside the
anticyclone are closely related to the photochemical lifetime of the
species, with strongest enhancement for shorter lived species. Vertical
profiles of the ratio of C2H2/CO (used to measure the relative age
of air) suggest relatively rapid transport of fresh emissions up to the
tropopause level inside the anticyclone.
Citation: Park, M., Randel, W. J., Emmons, L. K., Bernath, P. F., Walker, K. A., and Boone, C. D.: Chemical isolation in the Asian monsoon anticyclone observed in Atmospheric Chemistry Experiment (ACE-FTS) data, Atmos. Chem. Phys., 8, 757-764, doi:10.5194/acp-8-757-2008, 2008.