Dallas

1. Impacts of background ozone production on Houston and Dallas, TX Air Quality during the TexAQS field mission R. Bradley Pierce (NOAA/NESDIS), Jassim Al-Saadi (NASA/LaRC), Chieko Kittaka (NASA/LaRC), Todd Schaack (UW/SSEC), Allen Lenzen (UW /SSEC), Kevin Bowman (NASA/JPL), Jim Szykman (US/EPA), Amber Soja (NASA/LaRC), Tom Ryerson, (NOAA/ESRL), Anne M. Thompson (PSU), Pawan Bhartia (NASA/GSFC), Gary A. Morris (Valparaiso University) Requirement:Energy Policy Act of 2002, “Forecasts and Warnings” mandates NOAA to issue air quality forecasts and perform regional air quality assessments. Science: The Second Texas Air Quality Study (TEXAQS II) in 2006 focused on understanding the meteorological and chemical processes that lead to high-pollution events within both the Houston-Galveston-Brazoria (HGB) and Dallas-Fort Worth (DFW) ozone non-attainment areas, with a strong emphasis on regional processes. This poster presents a summary of a study addressing the influence of regional processes on the HGB/DFW metropolitan Statistical Areas (MSA) by quantifying the contributions of background (continental scale) ozone production on Houston and Dallas air quality during TexAQS II [Pierce et al., 2009]. Benefit:The TexAQS field studies support the Texas Commission on Environmental Quality (TCEQ) in developing State Implementation Plans (SIPs) for attaining National Ambient Air Quality Standards (NAAQS) for ozone in the HGB and DFW ozone non-attainment areas. 5) Ensemble back trajectories were computed for US EPA AIRNow sites in the Houston and Dallas MSA to determine background influences on Houston and Dallas O3. Bias corrected MSA and Background ozone predictions were compared to AIRNow observations. Lagrangian averaged O3 P-L was used for daily classification. Periods with mean ozone above 60ppbv (considered high ozone days in this analysis) are indicted by asterisks. 6) Houston inflow was dominated by moderate to enhanced background ozone production (Class 1&2) after August 28th, 2006 while Dallas was influenced by moderate to enhanced background ozone production throughout TEXAQS. The Lagrangian analysis shows that enhanced background O3 production was associated with 6 out of 9 periods with high O3 within the Houston MSA and 7 out of 15 periods with high O3 within the Dallas MSAduring the study period. Dallas Houston 7) Source apportionment studies show that 5-day Lagrangian averaged O3 P-L in excess of 15ppbv/day can occur during continental scale transport to Houston and Dallas due to NOy enhancements from emissions within the Southern Great Lakes as well as re-circulation of the Houston emissions. 1) The Real-time Air Quality Modeling System (RAQMS) is used in this study. RAQMS included assimilation of Ozone Monitoring Instrument (OMI) total column ozone retrievals and ozone and carbon monoxide retrievals from the Tropospheric Emission Spectrometer (TES). 2) The RAQMS Tropospheric Ozone Column (TOC) compares well with observational estimates of TOC . The RAQMS TOC analysis shows a slight (-1.26 DU) low bias over the continental US and a somewhat larger (-2.9 DU) bias over Texas during August 2006. Science Challenges:RAQMS tends to significantly underestimate NO2 variability, particularly at the high end of the observed NO2, thereby underestimating rapid daytime ozone production and nighttime ozone titration within urban plumes. This underestimate of urban photochemistry impacts our estimates of net O3 P-L within the urban centers that are identified as source regions in the Lagrangian analysis. Continental scale, high resolution modeling studies should be conducted to address these issues. Next Steps: Similar analyses will be conducted during the 2010 NOAA CalNex field mission. The objectives of CalNex are to address key science questions at the Nexus of air quality and climate change regarding influences of long-range transport, and characterization of ozone and aerosol precursors and greenhouse gas emissions within Southern California. Transition Path: Ensemble-mean Lagrangian sampling of CMAQ has been developed and applied to Baltimore [Fairlie et al., 2009] EPA is establishing a system to allow air quality planners to readily produce and access equivalent results for locations of their choice. 3) The RAQMS chemical analysis and ensemble Lagrangian trajectory techniques are used to characterize the amount of net ozone production (P-L) that occurs during synoptic scale transport prior to arrival in Houston and Dallas. Lagrangian sampling offers a complimentary approach to traditional methods of source apportionment based on air quality model emissions separation. 4) A region of high Lagrangian averaged O3 P-L (>15ppbv/day) extends across Texas from the Louisiana Gulf Coast towards New Mexico on September 2nd, 2006 and is associated with north-northwesterly surface winds behind a surface low pressure system that was centered over Virginia. Fairlie, T.D., Szykman, J., Gilliland, A., Pierce, R.B., Kittaka, C., Weber, S., Engel-Cox, J., Rogers, R.R., Tikvart, J., Scheffe, R., Dimmick, F. Lagrangian Sampling of 3-d Air Quality Model Results for Regional Transport Contributions to Sulfate Aerosol Concentrations at Baltimore, MD, in Summer 2004, Atmospheric Environment (2009), doi:10.1016/j.atmosenv.2009.02.026 Pierce, R. B., J. Al-Saadi, C. Kittaka, T. Schaack, A. Lenzen, K. Bowman, J. Szykman, A. Soja, T. Ryerson, A. M. Thompson, P. Bhartia, G. A. Morris, Impacts of background ozone production on Houston and Dallas, TX Air Quality during the TexAQS field mission, J. Geophys. Res., 114, D00F09, doi:10.1029/2008JD011337