Journal article

Trends in OMI NO2 observations over the United States: Effects of emission control technology and the economic recession

Russell A, Valin L, Cohen R ...see all

Atmospheric Chemistry and Physics, vol. 12, issue 24 (2012) pp. 12197-12209

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Observations of tropospheric NO2 vertical column densities over the
United States (US) for 2005-2011 are evaluated using the OMI Berkeley
High Resolution (BEHR) retrieval algorithm. We assess changes in NO2 on
day-of-week and interannual timescales to assess the impact of changes
in emissions from mobile and non-mobile sources on the observed trends.
We observe consistent decreases in cities across the US, with an average
total reduction of 32 +/- 7% across the 7 yr. Changes for large power
plants have been more variable (-26 +/- 12%) due to regionally-specific
regulation policies. An increasing trend of 10-20% in background NO2
columns in the northwestern US is observed. We examine the impact of the
economic recession on emissions and find that decreases in NO2 column
densities over cities were moderate prior to the recession (-6 +/- 5%
yr(-1)), larger during the recession (-8 +/- 5% yr(-1)), and then
smaller after the recession (-3 +/- 4% yr(-1)). Differences in the
trends observed on weekdays and weekends indicate that prior to the
economic recession, NO2 reductions were dominated by technological
improvements to the light-duty vehicle fleet but that a decrease in
diesel truck activity has contributed to emission reductions since the
recession. We use the satellite observations to estimate a 34% decrease
in NO2 from mobile sources in cities for 2005-2011 and use that value to
infer changes in non-mobile sources. We find that reductions in NO2 from
non-mobile sources in cities have been both more modest and more
variable than NO2 reductions from mobile sources (-10 +/- 13%).

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  • A. R. Russell

  • L. C. Valin

  • R. C. Cohen

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