Global Inventory of Nitrogen Oxide Emissions Constrained by Space-based
Observations of NO2 Columns
Randall V. Martin, Daniel J. Jacob, Kelly Chance, Thomas P. Kurosu, Paul
I. Palmer, Mathew J. Evans
and, Paul Ginoux
108(D17), 4537, doi:10.1029/2003JD003453, J. Geophys. Res., 2003.
We use tropospheric NO2 columns from the Global Ozone Monitoring Experiment
(GOME) satellite instrument to derive top-down constraints on emissions of
nitrogen oxides (NOx = NO + NO2), and combine these with a priori
information from a bottom-up emission inventory (with error weighting) to
achieve an optimized a posteriori estimate of the global distribution of surface NOx
emissions. Our GOME NO2 retrieval improves on previous work
by accounting for scattering and absorption of radiation by aerosols;
the effect on the air mass factor (AMF) ranges from +10% to -40% depending
on the region. Our AMF also includes local information on relative vertical
profiles (shape factors) of NO2 from
a global 3-D model of tropospheric chemistry (GEOS-CHEM); assumption of a
globally uniform shape factor, as in most previous retrievals, would
introduce regional biases of up to 40% over industrial regions and a factor
of 2 over remote regions.
We derive a top-down NOx emission inventory from the GOME data by using the
local GEOS-CHEM relationship between NO2 columns and NOx emissions.
The derived NOx emissions for industrial regions are aseasonal,
despite large seasonal variations in NO2 columns, providing
confidence in the method. Top-down errors in monthly NOx emissions are about 50%,
comparable to bottom-up errors over source regions. Annual global a
posteriori errors are half of a priori errors. Our global a posteriori
estimate for annual land surface NOx emissions (37.7 Tg N yr-1) agrees
closely with the GEIA-based a priori (36.4) and with an independent bottom-up inventory
(EDGAR 3.0) (36.6), but there are significant regional differences.
A posteriori NOx emissions are higher by 50-100% in
the Po Valley, Tehran, and Riyadh urban areas, and by 25-35% in Japan and
South Africa. Biomass burning emissions from India, central Africa, and
Brazil are lower by up to 50%; soil NOx emissions are appreciably higher in
the western United States, the Sahel, and southern Europe.
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