Remote sensed and in situ constraints on processes affecting tropical tropospheric ozone B. Sauvage1, R. V. Martin1,2, A. van Donkelaar1, X. Liu2, K. Chance2, L. Jaeglé3, P. I. Palmer4, S. Wu5, and T.-M. Fu5 1Department of Physics and Atmospheric Science, Dalhousie University, Halifax, Nova Scotia, Canada 2Atomic and Molecular Physics Division, Harvard-Smithsonian Center for Astrophysics, Cambridge, Massachusetts, USA 3Department of Atmospheric Sciences, University of Washington, Seattle, Washington, USA 4School of GeoSciences, University of Edinburgh, UK 5Department of Earth and Planetary Sciences and Division of Engineering and Applied Sciences, Harvard University, Cambridge, Massachusetts, USA
Abstract. We use a global chemical transport model (GEOS-Chem)
to evaluate the consistency of satellite
measurements of lightning flashes and ozone
precursors with in situ measurements of
tropical tropospheric ozone. The measurements
are tropospheric O3, NO2, and HCHO columns from the GOME satellite
instrument, lightning flashes from the OTD and LIS satellite instruments,
profiles of O3, CO, and relative humidity from the MOZAIC
aircraft program, and profiles of O3 from the SHADOZ ozonesonde
network. We interpret these multiple
data sources with our
model to better understand what controls tropical
tropospheric ozone. Tropical tropospheric ozone is mainly affected
by lightning NOx and convection in the upper troposphere and
by surface emissions in the lower troposphere.
Scaling the spatial
distribution of lightning in the model to the observed flashes improves the
simulation of O3 in the upper troposphere by 5–20 ppbv versus
in situ observations and by 1–4 Dobson Units versus GOME retrievals of tropospheric O3 columns.
A lightning source strength of 6±2 Tg N/yr best represents in situ observations from
aircraft and ozonesonde. Tropospheric NO2 and HCHO
columns from GOME are applied to provide top-down constraints on
emission inventories of NOx (biomass burning and soils) and VOCs
(biomass burning). The top-down
biomass burning inventory is larger than
the bottom-up inventory by a factor of 2 for HCHO and alkenes,
and by a factor of 2.6 for NOx over northern equatorial Africa. These emissions increase lower tropospheric O3
by 5–20 ppbv, improving the simulation versus aircraft observations,
and by 4 Dobson Units versus
GOME observations of tropospheric O3 columns. Emission factors in the a posteriori inventory are more
consistent with a recent compilation from in situ measurements. The ozone simulation
using two different dynamical schemes (GEOS-3 and GEOS-4) is
evaluated versus observations; GEOS-4 better represents O3
observations by 5–15 ppbv, reflecting enhanced convective detrainment in the
Heterogeneous uptake of HNO3 on aerosols reduces
simulated O3 by 5–7 ppbv, reducing a model bias versus in situ
observations over and downwind of deserts.
Exclusion of HO2 uptake on aerosols increases O3 by 5 ppbv in biomass burning regions,
reducing a model bias versus MOZAIC aircraft measurements.
Citation: Sauvage, B., Martin, R. V., van Donkelaar, A., Liu, X., Chance, K., Jaeglé, L., Palmer, P. I., Wu, S., and Fu, T.-M.: Remote sensed and in situ constraints on processes affecting tropical tropospheric ozone, Atmos. Chem. Phys., 7, 815-838, doi:10.5194/acp-7-815-2007, 2007.