Estimates of tropical bromoform emissions using an inversion method 1Department of Chemistry, University of Cambridge, Cambridge, UK
28 Jan 2014
2Met Office, Exeter, UK
3National Centre for Atmospheric Science, UK
*now at: School of Biosciences, University of Nottingham Malaysia Campus, Jalan Broga, 43500 Semenyih, Selangor Darul Ehsan, Malaysia
Received: 20 Jul 2013 – Published in Atmos. Chem. Phys. Discuss.: 06 Aug 2013 Abstract. Bromine plays an important role in ozone chemistry in both the troposphere
and stratosphere. When measured by mass, bromoform (CHBr3) is
thought to be the largest organic source of bromine to the atmosphere. While
seaweed and phytoplankton are known to be dominant sources, the size and the
geographical distribution of CHBr3 emissions remains uncertain.
Particularly little is known about emissions from the Maritime Continent,
which have usually been assumed to be large, and which appear to be
especially likely to reach the stratosphere. In this study we aim to reduce
this uncertainty by combining the first multi-annual set of CHBr3
measurements from this region, and an inversion process, to investigate
systematically the distribution and magnitude of CHBr3 emissions.
The novelty of our approach lies in the application of the inversion method
to CHBr3. We find that local measurements of a short-lived gas like
CHBr3 can be used to constrain emissions from only a relatively
small, sub-regional domain. We then obtain detailed estimates of
CHBr3 emissions within this area, which appear to be relatively
insensitive to the assumptions inherent in the inversion process. We
extrapolate this information to produce estimated emissions for the entire
tropics (defined as 20° S–20° N) of
225 Gg CHBr3 yr−1. The ocean in the area we base our
extrapolations upon is typically somewhat shallower, and more biologically
productive, than the tropical average. Despite this, our tropical estimate is
lower than most other recent studies, and suggests that CHBr3
emissions in the coastline-rich Maritime Continent may not be stronger than
emissions in other parts of the tropics.
Revised: 21 Nov 2013 – Accepted: 10 Dec 2013 – Published: 28 Jan 2014
Citation: Ashfold, M. J., Harris, N. R. P., Manning, A. J., Robinson, A. D., Warwick, N. J., and Pyle, J. A.: Estimates of tropical bromoform emissions using an inversion method, Atmos. Chem. Phys., 14, 979-994, doi:10.5194/acp-14-979-2014, 2014.