 |
| Titel |
Key chemical NOx sink uncertainties and how they influence top-down emissions of nitrogen oxides |
| VerfasserIn |
T. Stavrakou, J.-F. Müller, K. F. Boersma, R. J. der A., J. Kurokawa, T. Ohara, Q. Zhang |
| Medientyp |
Artikel
|
| Sprache |
Englisch
|
| ISSN |
1680-7316
|
| Digitales Dokument |
URL |
| Erschienen |
In: Atmospheric Chemistry and Physics ; 13, no. 17 ; Nr. 13, no. 17 (2013-09-10), S.9057-9082 |
| Datensatznummer |
250085686
|
| Publikation (Nr.) |
 copernicus.org/acp-13-9057-2013.pdf |
|
|
|
|
|
| Zusammenfassung |
Triggered by recent developments from laboratory and field studies regarding
major NOx sink pathways in the troposphere, this study evaluates
the influence of chemical uncertainties in NOx sinks for global
NOx distributions calculated by the IMAGESv2 chemistry-transport
model, and quantifies their significance for top-down NOx
emission estimates. Our study focuses on five key chemical parameters
believed to be of primary importance, more specifically, the rate of the
reaction of NO2 with OH radicals, the newly identified HNO3-forming
channel in the reaction of NO with HO2, the reactive uptake of N2O5
and HO2 by aerosols, and the regeneration of OH in the oxidation of
isoprene. Sensitivity simulations are performed to estimate the impact of
each source of uncertainty. The model calculations show that, although the
NO2+OH reaction is the largest NOx sink globally accounting
for ca. 60% of the total sink, the reactions contributing the most to the
overall uncertainty are the formation of HNO3 in NO+HO2, leading to
NOx column changes exceeding a factor of two over tropical
regions, and the uptake of HO2 by aqueous aerosols, in particular over
East and South Asia.
Emission inversion experiments are carried out using model settings which
either minimise (MINLOSS) or maximise (MAXLOSS) the total NOx
sink, both constrained by one year of OMI NO2 column data from the DOMINO
v2 KNMI algorithm. The choice of the model setup is found to have a major
impact on the top-down flux estimates, with 75% higher emissions for
MAXLOSS compared to the MINLOSS inversion globally. Even larger departures
are found for soil NO (factor of 2) and lightning (1.8). The global
anthropogenic source is better constrained (factor of 1.57) than the natural
sources, except over South Asia where the combined uncertainty primarily
associated to the NO+HO2 reaction in summer and HO2 uptake by aerosol
in winter lead to top-down emission differences exceeding a factor of 2.
Evaluation of the emission optimisation is performed against independent
satellite observations from the SCIAMACHY sensor, with airborne NO2
measurements of the INTEX-A and INTEX-B campaigns, as well as with two new
bottom-up inventories of anthropogenic emissions in Asia (REASv2) and China
(MEIC). Neither the MINLOSS nor the MAXLOSS setup succeeds in providing the
best possible match with all independent datasets. Whereas the minimum sink
assumption leads to better agreement with aircraft NO2 profile
measurements, consistent with the results of a previous analysis
(Henderson et al., 2012), the same assumption leads to unrealistic features in the
inferred distribution of emissions over China. Clearly, although our study
addresses an important issue which was largely overlooked in previous
inversion exercises, and demonstrates the strong influence of NOx
loss uncertainties on top-down emission fluxes, additional processes need to
be considered which could also influence the inferred source. |
| |
|
| Teil von |
|
|
|
|
|
|
|
|