Air Pollutant Concentrations and Trends over the Eastern U.S. and China: Aircraft Measurements and Numerical Simulations
Air Pollutant Concentrations and Trends over the Eastern U.S. and China: Aircraft Measurements and Numerical Simulations
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Date
2012
Authors
He, Hao
Advisor
Dickerson, Russell R.
Citation
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Abstract
In the last several decades, efforts have been made to mitigate air pollution all
around the world. With surface observations showing substantial decrease of criteria
pollutants, including O3, NOx, CO and SO2, the long-term aircraft measurements over
the eastern U.S. provide a unique opportunity to study the trend of the air pollutant
column contents and the regional transport in the free troposphere. Analyses of the
historical data indicated ~2.0 Dobson Unit/decade decrease in tropospheric O3
columns over the eastern U.S. with a similar decreasing trend of CO. The statistical
analysis also showed a significant decreasing trend for tropospheric SO2. Analyses of
the EPA CEMS emission data showed parallel reductions. A case study of
tropospheric O3 and SO2 over downwind area of Baltimore showed that the regional
transport by westerly wind from Ohio and Pennsylvania play an important role in the
local air quality issues.
As the second largest economy in the world, China's rapid economic growth
in the last decade lead to a dramatic increase in energy demand, which relied heavily
on coal burning. The enormous amount of SO2 emissions caused severe
environmental issues including acid deposition and particulate matter pollution. To
mitigate these air quality problems, strict control measures and regulations were
applied to abate sulfur emissions, especially before and during the 2008 Beijing
Olympics. Aircraft measurements of tropospheric SO2 were conducted over central
China in spring 2008, where intense measurements are lacking. A substantial amount
of SO2 was observed in the free troposphere, which is important to regional transport
and remote sensing. I successfully validated the SO2 columns with satellite retrievals,
and proved that the new OMI SO2 algorithm performs better than the conventional
algorithm. An emission inventory was evaluated through a combination of model
simulations and satellite products. Between 2006 and 2008, the SO2 emissions had
been reduced substantially over middle and eastern China. I also analyzed the model
simulations, and find the SO2 lifetime is ~ 38 h during spring in China and that ~50%
of Chinese emissions are exported to the western Pacific.