Eighth Symposium on the Urban Environment
Eighth Conference on Coastal Atmospheric and Oceanic Prediction and Processes
Special Symposium on Measurements in the Urban Environment and Observations


Dependence of peak daily ozone concentrations in Houston, Texas on the sea breeze and meteorological variables

Robert M. Banta, NOAA/ESRL, Boulder, CO; and C. J. Senff, R. J. Alvarez, D. D. Parrish, M. K. Trainer, T. B. Ryerson, L. S. Darby, R. M. Hardesty, B. Lambeth, J. A. Neuman, W. M. Andevine, J. W. Nielsen-Gammon, S. P. Sandberg, A. O. Langford, and A. B. White

A flow reversal during the onset of the sea breeze near Houston, Texas was shown in a previously published study to be a critical factor in the production of the highest ozone (O3) concentrations measured during the Texas 2000 Air Quality Study (TexAQS2000). This flow reversal produced a recirculation of pollutants back over the emission source regions and also produced a 1-2 h period of stagnation along the sea-breeze front, which allowed pollutants to accumulate over the source regions. To further investigate the role of wind speed in determining ozone concentration, we determined peak daily ozone for all airborne study days during the 2000 and 2006 Texas studies, and we calculated vector-averaged mean wind speed between 200 and 500m AGL in the lower boundary layer for each day. Ozone concentrations were determined from airborne O3 Differential Absorption Lidar (DIAL), which surveyed and mapped out the horizontal and vertical structure of the Houston ozone plume. Scatter plots and regression analysis of these ozone vs. wind speed variables revealed high correlations (r2~0.8-0.9), the lowest wind speeds corresponding to the highest ozone. Attempts to include the effects of boundary-layer height h and daily maximum temperature Tmax showed no improvement in the correlations, indicating that wind speed was the primary meteorological control on daily peak O3, and that h and Tmax did not have perceptible effects. Ozone vs. wind speed plots made for TexAQS2000 and TexAQS2006 showed that the 2000 regression line lay significantly above the 2006 line at small wind speeds (high concentrations) converging to no significant difference at speeds of 5 m/s or more. In other words, emission-control measures implemented between 2000 and 2006 were effective in improving the air quality in the Houston area, with the greatest improvement evident on the worst pollution days.

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Joint Session 13, Joint Session on Air Quality Measurements in Coastal Cities
Tuesday, 13 January 2009, 11:00 AM-12:00 PM, Room 124A

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