Direct measurement of ozone production rates in Houston in 2009 and comparison with two estimation methods
1Department of Meteorology, Pennsylvania State University, University Park, PA, USA
2Rosentiel School of Marine and Atmospheric Science, University of Miami, FL, USA
3Department of Earth and Atmospheric Sciences, University of Houston, Houston, TX, USA
*now at: Atmospheric Chemistry and Dynamics Branch, NASA Goddard Space Flight Center, Greenbelt, MD, USA
**now at: Air Resources Laboratory, National Oceanic and Atmospheric Administration, Silver Spring, MD, USA
Abstract. Ozone production rates, P(O3), were measured directly using the Penn State Measurement of Ozone Production Sensor (MOPS) during the Study of Houston Atmospheric Radical Precursors (SHARP 2009). Measured P(O3) peaked in the late morning, with values between 15 ppbv h−1 and 100 ppbv h−1, although values of 40–80 ppbv h−1 were typical for higher ozone days. These measurements were compared against ozone production rates calculated using measurements of hydroperoxyl (HO2), hydroxyl (OH), and nitric oxide (NO) radicals, called "calculated P(O3)". The same comparison was done using modeled radicals obtained from a box model with the RACM2 mechanism, called "modeled P(O3)". Measured and calculated P(O3) had similar peak values but the calculated P(O3) tended to peak earlier in the morning when NO values were higher. Measured and modeled P(O3) had a similar dependence on NO, but the modeled P(O3) was only half the measured P(O3). This difference indicates possible missing radical sources in the box model with the RACM2 mechanism and thus has implications for the ability of air quality models to accurately predict ozone production rates.