On the relationship between acetone and carbon monoxide in different air masses
Marian de Reus1 , Horst Fischer1, Joost de Gouw2,
Carsten Warneke2, Jonathan Williams1 and Frank Arnold3
1 Max Planck Institute for Chemistry, Mainz, Germany (reus@mpch-mainz.mpg.de)
2 NOAA Aeronomy Laboratory, Boulder, USA
3 Max Planck Institute for Nuclear Physics, Heidelberg, Germany
Carbon monoxide and acetone measurements are presented for five airborne measurement campaigns
at mid-latitudes, polar and tropical areas in the northern hemisphere. Throughout all campaigns,
free tropospheric air masses, which were influenced by anthropogenic emissions, showed a similar
linear relation between CO and acetone, with a slope of 21 pptv acetone/ppbv CO. Measurements in
the, anthropogenically disturbed, marine boundary layer revealed a slope of 15 pptv acetone/ppbv
CO. The reduced slope in the marine boundary layer indicates acetone uptake by the ocean. In the
lowermost stratosphere, a good correlation between CO and acetone was observed as well, however,
with a much smaller slope (5 pptv acetone/ppbv CO) as in the troposphere. This is caused by the
longer lifetime of CO compared to acetone in the lower stratosphere, due to the photolysis of
acetone. No significant correlation between CO and acetone was observed over the tropical rain
forest due to the large biogenic emissions of acetone and acetone precursor gases.
The common slopes of the linear CO-acetone relation in various layers of the atmosphere, during
five field experiments, makes them useful for model calculations. Up till now, a single
observation of the CO-acetone correlation, determined from stratospheric measurements, has been
used in several box model studies. This study shows that different slopes have to be considered
for marine boundary layer, free tropospheric and stratospheric air masses, and that the
CO-acetone relation cannot be used for air masses which are strongly influenced by biogenic
emissions. Moreover, the observed slopes can be very useful for air mass identification.