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| Titel |
Emissions of nitrogen oxides from US urban areas: estimation from Ozone Monitoring Instrument retrievals for 2005–2014 |
| VerfasserIn |
Z. Lu, D. G. Streets, B. de Foy, L. N. Lamsal, B. N. Duncan, J. Xing |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1680-7316
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| Digitales Dokument |
URL |
| Erschienen |
In: Atmospheric Chemistry and Physics ; 15, no. 18 ; Nr. 15, no. 18 (2015-09-21), S.10367-10383 |
| Datensatznummer |
250120041
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| Publikation (Nr.) |
 copernicus.org/acp-15-10367-2015.pdf |
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| Zusammenfassung |
| Satellite remote sensing of tropospheric nitrogen dioxide (NO2) can
provide valuable information for estimating surface nitrogen oxides
(NOx) emissions. Using an exponentially modified Gaussian (EMG) method
and taking into account the effect of wind on observed NO2
distributions, we estimate 3-year moving-average emissions of summertime
NOx from 35 US (United States) urban areas directly from NO2 retrievals of the
Ozone Monitoring Instrument (OMI) during 2005–2014. Following conclusions
of previous studies that the EMG method provides robust and accurate
emission estimates under strong-wind conditions, we derive top-down NOx
emissions from each urban area by applying the EMG method to OMI data with
wind speeds greater than 3–5 m s−1. Meanwhile, we find that OMI
NO2 observations under weak-wind conditions (i.e., < 3 m s−1) are qualitatively better correlated to the surface NOx source
strength in comparison to all-wind OMI maps; therefore, we use them to
calculate the satellite-observed NO2 burdens of urban areas and compare
with NOx emission estimates. The EMG results show that OMI-derived
NOx emissions are highly correlated (R > 0.93) with weak-wind
OMI NO2 burdens as well as with bottom-up NOx emission estimates
over 35 urban areas, implying a linear response of the OMI observations to
surface emissions under weak-wind conditions. The simultaneous EMG-obtained
effective NO2 lifetimes (~ 3.5 ± 1.3 h), however,
are biased low in comparison to the summertime NO2 chemical lifetimes.
In general, isolated urban areas with NOx emission intensities greater
than ~ 2 Mg h−1 produce statistically significant
weak-wind signals in 3-year average OMI data. From 2005 to 2014, we
estimate that total OMI-derived NOx emissions over all selected US
urban areas decreased by 49 %, consistent with reductions of 43,
47, 49, and 44 % in the total bottom-up NOx emissions, the
sum of weak-wind OMI NO2 columns, the total weak-wind OMI NO2
burdens, and the averaged NO2 concentrations, respectively, reflecting
the success of NOx control programs for both mobile sources and power
plants. The decrease rates of these NOx-related quantities are found to
be faster (i.e., −6.8 to −9.3 % yr−1) before 2010 and slower
(i.e., −3.4 to −4.9 % yr−1) after 2010. For individual urban
areas, we calculate the R values of pair-wise trends among the OMI-derived
and bottom-up NOx emissions, the weak-wind OMI NO2 burdens, and
ground-based NO2 measurements, and high correlations are found for all
urban areas (median R= 0.8), particularly large ones (R up to 0.97). The
results of the current work indicate that using the EMG method and
considering the wind effect, the OMI data allow for the estimation of
NOx emissions from urban areas and the direct constraint of emission
trends with reasonable accuracy. |
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