Figure 1 : August 2006 RAQMS and Observed TOC

1. Impacts of background ozone production on Houston and Dallas, TX Air Quality during the TexAQS field mission R. Bradley Pierce1 (GOVERNMENT PRINCIPAL INVESTIGATOR)Jassim Al-Saadi2, Amber Soja2 and Chieko Kittaka2, Todd Schaack3 and Allen Lenzen3, Kevin Bowman4, Jim Szykman5, Tom Ryerson6, Anne M. Thompson7, Pawan Bhartia8, Gary A. Morris9 1NOAA/NESDIS, 2NASA/LaRC, 3UW /SSEC, 4NASA/JPL, 5US/EPA, 6NOAA/ESRL, 7PSU, 8NASA/GSFC, 9Valparaiso University Requirement:Provide information to air quality decision makers and improve NOAA’s national air quality forecast capability Science:What were the contributions of background, continental scale ozone production on Houston-Galveston-Brazoria (HGB) and Dallas-Fort Worth (DFW) ozone non-attainment areasduring the 2006 Second Texas Air Quality Study (TexAQS II)? 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. • 1) The Real-time Air Quality Modeling System (RAQMS) is used in this study [Pierce et al, 2009]. The RAQMS TexAQS analysis includes assimilation of Ozone Monitoring Instrument (OMI) total column ozone retrievals and ozone and carbon monoxide retrievals from the Tropospheric Emission Spectrometer (TES). • 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 (Figure 1). • 2) 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. • A region of Enhanced 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 (Figure 2). Figure 1: August 2006 RAQMS and Observed TOC • 3) Ensemble back trajectories were computed for US EPA AIRNow sites in the Houston and Dallas Metropolitan Statistical Areas (MSA) to determine background influences on Houston and Dallas O3. Bias corrected MSA and Background ozone predictions were compared to AIRNow observations (Figure 3). 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. • 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 Figure 2: September 2nd, 2006 Lagrangian averaged O3 P-L Figure 3: Bias corrected RAQMS MSA and Background mean O3 vs AIRNow observations • Science Challenges:Underestimates of urban photochemistry due to the • relatively coarse (2ox2o) horizontal resolution of the RAQMS chemical analysis • impacts estimates of net O3 P-L within the urban source regions. • Continental scale, high resolution modeling studies should be conducted to • address these issues. • Next Steps:RAQMS Lagrangian chemical 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:The US EPA is establishing a system to allow air quality • planners to produce and access equivalent results for locations of their choice. • Lagrangian photochemical sampling of CMAQ has been developed and applied • to Baltimore, MD air quality studies [Fairlie et al, 2009]. 4) 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 (Figure 4). References: Pierce, R. B., et al, (2009), 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 Fairlie, T.D., et al., (2009), 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, doi:10.1016/j.atmosenv.2009.02.026 The views, opinions, and findings contained in this study are those of the authors and should not be construed as an official National Oceanic and Atmospheric Administration or U.S. Government position, policy, or decision. Figure 4: Source contributions to Dallas and Houston during periods of enhanced (Class 1) background O3 P-L