Acetylene C2H 2 retrievals from MIPAS data and regions of enhanced upper tropospheric concentrations in August 2003 Earth Observation Science, Space Research Centre, University of Leicester, Leicester, UK
13 Oct 2011
Received: 11 Aug 2010 – Published in Atmos. Chem. Phys. Discuss.: 07 Dec 2010 Abstract. Acetylene (C2H2) volume mixing ratios (VMRs) have been successfully
retrieved from the Michelson Interferometer for Passive Atmospheric Sounding
(MIPAS) Level 1B radiances during August 2003, providing the first global map
of such data and ratios to CO in the literature. The data presented here
contain most information between 300 hPa and 100 hPa with systematic errors
less than 10% at the upper levels. Random errors per point are less than
15% at lower levels and are closer to 30% at 100 hPa.
Revised: 28 Sep 2011 – Accepted: 29 Sep 2011 – Published: 13 Oct 2011
Global distributions of the C2H2 and C2H2/CO ratio confirm
significant features associated with both the Asian monsoon anticyclone and
biomass burning for this important hydrocarbon in a characteristic summer
month (August 2003), showing tight correlations regionally, particularly at
lower to medium values, but globally emphasising the differences between
sources and lifetimes of CO and C2H2. The correlations are seen to be
particularly disturbed in the regions of highest C2H2 concentrations,
indicating variability in the surface emissions or fast processing.
A strong isolation of C2H2 within the Asian monsoon anticyclone is
observed, evidencing convective transport into the upper troposphere,
horizontal advection within the anticyclone at 200 hPa, distinct gradients
at the westward edge of the vortex and formation of a secondary dynamical
feature from the eastward extension of the anticyclone outflow over the Asian
Pacific. Ratios of C2H2/CO are consistent with the evidence from the
cross-sections that the C2H2 is uplifted rapidly in convection.
Observations are presented of enhanced C2H2 associated with the
injection from biomass burning into the upper troposphere and the outflow
from Africa at 200 hPa into both the Atlantic and Indian Oceans. In the
biomass burning regions, C2H2 and CO are well correlated, but the
uplift is less marked and peaks at lower altitudes compared to the strong
effects observed in the Asian monsoon anticyclone. Ratios of C2H2/CO
clearly decay along transport pathways for the outflow, indicating
photochemical ageing of the plumes.
Overall, the data show the distinctive nature of C2H2 distributions,
confirm in greater detail than previously possible features of hydrocarbon
enhancements in the upper troposphere and highlight the future use of MIPAS
hydrocarbon data for testing model transport and OH decay regimes in the
middle to upper troposphere.
Citation: Parker, R. J., Remedios, J. J., Moore, D. P., and Kanawade, V. P.: Acetylene C2H 2 retrievals from MIPAS data and regions of enhanced upper tropospheric concentrations in August 2003, Atmos. Chem. Phys., 11, 10243-10257, doi:10.5194/acp-11-10243-2011, 2011.