Characterization of Regional Wind Patterns Using Self-Organizing Maps: Impact on Dallas-Fort Worth Long-Term Ozone Trends

摘要

This study analyzes wind patterns in the Dallas-Fort Worth (DFW) area to gain a clearer understanding of meteorological patterns that have historically led to ozone exceedances in this region. Using a clustering algorithm called "self-organizing maps," we analyzed five notable characteristic regional wind patterns that occurred between April and October in 2000-14. A regional-scale high pressure system, cluster 2, produced weak southeast winds over DFW and accounted for 35.2% of ozone exceedances. Clusters 1 and 5, characterized by southwesterly winds over the DFW area, were together associated with one-third of total ozone exceedances and show quantifiable impacts of the Barnett Shale region on downwind ozone production. Cluster 3, associated with Bermuda-high conditions, had relatively lower ozone in DFW (45.3 ppbv) resulting from transport of lower background ozone from the Gulf of Mexico. For clusters that produce southeasterly or southwesterly winds over Houston, ozone values in DFW were always larger than those in Houston. Further, to determine the potential impact of Houston pollution on DFW ozone, a sensitivity simulation with no Houston emissions and a base simulation were performed. The difference between the simulations revealed ozone enhancements of 1-2 ppbv and coincident enhancements in NOy under south-southeasterly wind conditions. From these results, we conclude that downwind pollution from Houston and the Barnett Shale area exacerbates DFW ozone concentrations, underscoring the impacts of specific wind patterns on air quality in DFW.