A method for evaluating spatially-resolved NOx emissions using Kalman filter inversion, direct sensitivities, and space-based NO2 observations
Other literature type
Napelenok, S. L.
Pinder, R. W.
Gilliland, A. B.
Martin, R. V.
(issn: 1680-7324, eissn: 1680-7324)
An inverse modeling method was developed and tested for identifying possible
biases in emission inventories using satellite observations. The
relationships between emission inputs and modeled ambient concentrations were
estimated using sensitivities calculated with the decoupled direct method in
three dimensions (DDM-3D) implemented within the framework of the Community
Multiscale Air Quality (CMAQ) regional model. As a case study to test the
approach, the method was applied to regional ground-level NO<sub>x</sub>
emissions in the southeastern United States as constrained by observations of
NO<sub>2</sub> column densities derived from the Scanning Imaging Absorption
Spectrometer for Atmospheric Chartography (SCIAMACHY) satellite instrument. A
controlled "pseudodata" scenario with a known solution was used to
establish that the methodology can achieve the correct solution, and the
approach was then applied to a summer 2004 period where the satellite data
are available. The results indicate that emissions biases differ in urban and
rural areas of the southeast. The method suggested slight downward (less than
10%) adjustment to urban emissions, while rural region results were found to
be highly sensitive to NO<sub>x</sub> processes in the upper troposphere. As
such, the bias in the rural areas is likely not solely due to biases in the
ground-level emissions. It was found that CMAQ was unable to predict the
significant level of NO<sub>2</sub> in the upper troposphere that was observed during
the NASA Intercontinental Chemical Transport Experiment (INTEX) measurement
campaign. The best correlation between satellite observations and modeled
NO<sub>2</sub> column densities, as well as comparison to ground-level observations
of NO<sub>2</sub>, was obtained by performing the inverse while accounting for the
significant presence of NO<sub>2</sub> in the upper troposphere not captured by the