Scientific Theme: Advanced Modeling and Observing Systems

Scientific Theme: Regional Processes
MILESTONE CSD08.2:
Evaluate sulfur dioxide emissions from power plants sampled during the New England Air Quality
Study campaign using new ultraviolet spectroscopy methods.
ACCOMPLISHMENTS FOR CSD08.2:
Sulfur dioxide (SO2) emissions are regulated under the National Ambient Air Quality Standards (NAAQS) as
criteria pollutants due to their role in the formation of acid rain. However, SO2 also contributes to other atmospheric
chemistry processes such as the formation of sulfur-containing particles that play a critical role in climate change.
The main emitter of SO2 in the United States is power plants, which account for 67% of the SO2 released into the
atmosphere. Accurate measurements of SO2 from power points are therefore critical in order to understand their
impacts on regional air quality.
Therefore, a near-ultraviolet (UV) spectrometer was deployed during the New England Air Quality Study 2004
(NEAQS2K4) aboard the NOAA WP-3D aircraft to measure SO2 emissions from point sources. Using the
differential optical absorption spectroscopy (DOAS) method, SO2 and oxygen dimer (O4) differential slant-column
densities are retrieved from the UV spectra. The SO2 differential slant-column densities are used to identify point
source plumes. In a novel approach, the O4 differential slant-column densities are used to calculate an air mass
factor (AMF) or path-length enhancement of photons through the atmosphere. The AMF is used to convert the SO2
differential slant-column densities into SO2 differential vertical-column densities. From the SO2 differential verticalcolumn
densities, SO2 emission fluxes from point sources sampled during NEAQS2K4 are calculated. The measured
SO2 emission fluxes are compared to the reported SO2 emission fluxes from the point sources. The results show
good agreement between the measured and the reported point sources of SO2 emission fluxes.
MILESTONE CSD08.3:
Gather data during the 2006 Texas Air Quality study to investigate the role of meteorological
processes in transport and mixing of pollutant species in the nighttime stable boundary layer
(SBL).
ACCOMPLISHMENTS FOR CSD08.3:
The NOAA ship-based Doppler lidar was used to investigate the structure of the nighttime boundary layer over the
Gulf of Mexico, corresponding to a marine boundary layer, and close to shore near Houston and Galveston, where
the environment was more indicative of a terrestrial boundary layer. In the Gulf, CIRES researchers found that
Doppler lidar-derived mixing heights and flux-tower surface heat flux measurements showed little to no indication
of a diurnal cycle. Closer to shore, in places like Barbour‘s Cut and the Houston Ship Channel, they observed
frequent nocturnal low-level jets that were always followed by low-ozone days (as measured in those locations).
Depending on background levels and other atmospheric conditions, nights with low-wind speeds (i.e., without
nocturnal low-level jets) were more likely to be followed by high ozone days. At the Galveston Bay and ship
channel locations, strong diurnal cycle characteristics in lidar-derived mixing layer heights were also observed, with
nighttime mixing heights as low as 150 meters during low-level jets, and up to 500 meters during nights with lowwind
speed profiles.
MILESTONE CSD08.4:
Contribute to the 2006 TexAQS/GoMACCS Air Quality Study in the Houston, TX, vicinity by
deploying several lidars on an aircraft and a research ship.
ACCOMPLISHMENTS FOR CSD08.4:
An airborne ozone lidar and two shipborne lidars (a Doppler wind lidar and another ozone and aerosol profiling
lidar) were successfully deployed during the 2006 Texas Air Quality Study (TexAQS II). These three remotesensing
systems produced extensive, multi-dimensional data sets of wind speed, wind direction, atmospheric
turbulence, ozone concentration, aerosol backscatter and extinction, and mixed-layer height. Results obtained from
the analysis of these data sets will be key in addressing several important science questions regarding local buildup
and regional transport of pollutants in eastern Texas. The analysis of the lidar data sets is ongoing, but several
important findings have already emerged and these results have been presented at the TexAQS II Principal Findings
Data Analysis Workshop in Austin, TX, at the end of May 2007.
92