HR: 0800h
AN: A51B-0353 INVITED    [Abstracts]
TI: Factors Controlling Peak Ozone Concentrations in the Houston Area: Wind Speed and Mixing Height
AU: * Banta, R M
EM: robert.banta@noaa.gov
AF: NOAA/ESRL, 325 Broadway, Boulder, CO 80305, United States
AU: Senff, C J
EM: christoph.senff@noaa.gov
AF: CIRES, 325 Broadway, Boulder, CO 80305, United States
AU: Nielsen-Gammon, J W
EM: n-g@tamu.edu
AF: Department of Meteorology, Texas A & M University, College Station, TX 77843, United States
AU: Lambeth, B
EM: BLAMBETH@tceq.state.tx.us
AF: Texas Commission on Environmental Quality, P.O. Box 13087, Austin, TX 78711, United States
AU: Trainer, M K
EM: michael.k.trainer@noaa.gov
AF: NOAA/ESRL, 325 Broadway, Boulder, CO 80305, United States
AU: Alvarez, R J
EM: raul.alvarez@noaa.gov
AF: NOAA/ESRL, 325 Broadway, Boulder, CO 80305, United States
AU: Hardesty, R M
EM: michael.hardesty@noaa.gov
AF: NOAA/ESRL, 325 Broadway, Boulder, CO 80305, United States
AU: Ryerson, T B
EM: Thomas.B.Ryerson@noaa.gov
AF: NOAA/ESRL, 325 Broadway, Boulder, CO 80305, United States
AU: Frost, G J
EM: Gregory.J.Frost@noaa.gov
AF: CIRES, 325 Broadway, Boulder, CO 80305, United States
AU: Darby, L S
EM: lisa.darby@noaa.gov
AF: NOAA/ESRL, 325 Broadway, Boulder, CO 80305, United States
AU: White, A B
EM: Allen.B.White@noaa.gov
AF: CIRES, 325 Broadway, Boulder, CO 80305, United States
AB: Peak daytime concentrations of pollutants such as ozone (O3) are inversely dependent on wind speed and mixing depth. Although this relationship is well known and forms the basis of schemes for forecasting maximum daily pollutant concentrations, few data sets comprehensive enough to test this dependence are available. Here we use the data sets from the Texas Air Quality Study (TexAQS) campaigns in the Houston-Galveston Bay area during the summers of 2000 and 2006 to investigate this relationship. Advantages of the TexAQS data sets are (1) the availability of airborne measurements using in-situ and ozone Differential-Absorption Lidar (DIAL) instrumentation, which are able to locate peak O3 concentrations even when they occur outside the surface measurement network, and (2) availability of a network of radar wind profilers, which provide mean boundary- layer winds above the surface at intervals of 1 hr or less. The availability of such wind data is important, because the highest O3 concentrations are associated with midday to early afternoon wind reversals due to the sea breeze. Days with both airborne and surface O3 measurements in the Houston-Galveston-Bay area were selected for analysis. Peak O3 values were determined for a given day from the airborne lidar or P-3 flight data and for the surface measurement network. 10-hr trajectories were calculated from the profiler array and used to calculate the vector-averaged wind speed during this time interval. This procedure accounts for the sea-breeze wind reversals in the accumulation of pollutants. Mixing heights were determined from the aerosol profiles from the airborne lidar when available, or otherwise from the nearest radar wind profiler. To determine the effects of background pollutant levels, background O3 concentration was determined from upstream rural sites in the surface measurement network. The background values were subtracted from the peak concentrations to determine how much O3 was due to the Houston urban / Ship Channel contribution, or urban "add-on." The results confirmed the strong dependence of maximum daily O3 concentrations on the mean wind speed. The highest concentrations and add-on concentrations occurred with vector-averaged speeds of 3 m/s or less, with strong increases to greater than 150 ppb as the speeds decreased to ~1 m/s. At higher wind speeds, peak O3 concentrations tended to be less than 100 ppb and add-ons less than 60 ppb, although some individual days had higher peak O3 associated with high background values. Mixing heights mostly had a secondary effect on peak and add-on concentrations, although this effect was stronger on individual days or at certain times of the day, such as during morning offshore flow conditions before the onset of the sea breeze.
DE: 0300 ATMOSPHERIC COMPOSITION AND STRUCTURE
DE: 0345 Pollution: urban and regional (0305, 0478, 4251)
DE: 0365 Troposphere: composition and chemistry
DE: 0368 Troposphere: constituent transport and chemistry
SC: Atmospheric Sciences [A]
MN: 2007 Fall Meeting