OTAG Air Quality Analysis Workgroup
Description of the Air Quality Analysis WG
Types of Analyses
Exceedance Areas for 1hr-120 ppb and 8-hr-80 ppb Standards
Area source NOx emissions are highest near cities. Point sources dominate the center of OTAG
The corners of the OTAG domain are mostly at tropospheric background levels
Generally increasing trend from west to east in the direction of the prevailing air transport
Highest (90 %-ile) concentrations near urban areas. Lowest (10 %) ozone is high in the central domain
The largest ozone variability (90-10 %-ile difference) occurs near urban areas.
High O3 (90%-ile) days are associated with stagnation in the S.E. and transport in the N.E.
Low O3 (10%-ile) days are associated with transport from outside into the OTAG domain.
OTAG-wide episodes tend to be associated with stagnation followed by transport.
Transport in the N.E. occurs in synoptic, channeled, and near surface flow regimes
AQ data analysis suggest 1.5-2 days between emissions and removal and 300-500 mile transport
Model-derived transport scales are 150-200 miles. Is model underestimating ozone transport?
Ozone events last longer in the South (2-3 days) and shorter (1-2 days) in the North.
OTAG is a well defined control region. Low O3 air comes from outside, high O3 air from inside OTAG.
Emission changes do change O3 levels. 120 ppb exceedances are 3X higher on Fridays than Sundays
Long-term O3 trends also show that many control efforts have reduced the ozone levels
Control of sources in central OTAG domain may provide downwind benefits in all directions.
Home Page: http://capita.wustl.edu/