Environmental Engineering Reference
In-Depth Information
4.16 Satellite Based Investigations of Day-of-Week
Variation in NO
x
Emissions
Ashley Ray Russell
1
, Lukas Valin
1
, Simon Schmutz
2
, Pascal Tay
2
,
and Ron Cohen
1
1
Department of Chemistry, University of California, Berkeley, CA, USA
2
Swiss Federal Institute of Technology, Institute for Atmospheric and Climate Science,
Zurich, Switzerland
Abstract
In the state of California, mobile sources account for more than 50% of
NO
x
emissions. Regulation focusing on passenger vehicles has led to dramatic
reductions in total NO
x
emissions. Heavy-duty diesel vehicle emissions have, in
contrast, not decreased and therefore represent a growing fraction of total NO
x
emissions. A pronounced weekend effect, marked by a substantial decrease in
measured NO
2
on weekends when compared with measurements on weekdays has
been observed in some urban areas of the state due to variation in the activity
patterns of these two types of vehicles. We examine this weekend effect using
observations from the Ozone Monitoring Instrument (OMI). We developed a high
resolution (5 × 5 km
2
) average of the OMI observations that permits a detailed
view of spatial variations in emissions with day of week. Comparison of the
observations to emission inventories suggests opportunities for improvements and
for assessing differences between San Joaquin Valley and South Coast Air Basins.
Keywords
OMI, Satellite, Day-of-week, NOx, Emissions, Urban
1. Introduction
We use satellite observations from the Ozone Monitoring Instrument (OMI)
aboard the Aura satellite to monitor variation of NO
2
columns with day of week.
In the state of California, mobile sources account for a large majority of NO
x
emissions. Regulation aimed at reducing these emissions has to date focused
primarily on light-duty passenger vehicles yielding a relative increase in the
importance of heavy duty diesel truck NO
x
emissions. The 'weekend effect' is the
name given to the trend in regional NO
x
levels in which we see a substantial
decrease in weekend concentrations relative to weekday levels. In California, this
is due mainly to the different activity patterns of these two mobile source types.
