Mass balance inverse modelling of methane in the 1990s using a Chemistry Transport Model T. M. Butler1,*, I. Simmonds1, and P. J. Rayner2 1School of Earth Sciences, Melbourne University, Australia 2CSIRO Atmospheric Research, Melbourne, Australia *Present affiliation: Max Planck Institute for Chemistry, Mainz, Germany
Abstract. A mass balance inverse modelling procedure is applied with a time-dependent
methane concentration boundary condition and a chemical transport model
to relate observed changes
in the surface distribution of methane mixing ratios during the 1990s
to changes in its surface sources.
The model reproduces essential
features of the global methane cycle, such as the latitudinal distribution
and seasonal cycle of fluxes, without using a priori knowledge of
A detailed description of the temporal and spatial variability of
the fluxes diagnosed by the inverse procedure is presented,
and compared with previously hypothesised changes in the methane budget,
and previous inverse modelling studies.
The sensitivity of the inverse results to the forcing data supplied by
surface measurements of methane from the NOAA CMDL cooperative air
sampling network is also examined.
This work serves as an important starting point for future inverse modelling
work examining changes in both the source and sink terms in the methane budget
Citation: Butler, T. M., Simmonds, I., and Rayner, P. J.: Mass balance inverse modelling of methane in the 1990s using a Chemistry Transport Model, Atmos. Chem. Phys., 4, 2561-2580, doi:10.5194/acp-4-2561-2004, 2004.