HR: 16:30h
AN: A54B-03    [Abstracts]
TI: Climate Effects on Ozone Concentrations in California
AU: * Mahmud, A
EM: aamahmud@ucdavis.edu
AF: UCD Department of Civil and Environmental Engineering, 1 Shields Ave, Davis, CA 95616, United States
AU: Kleeman, M
EM: mjkleeman@ucdavis.edu
AF: UCD Department of Civil and Environmental Engineering, 1 Shields Ave, Davis, CA 95616, United States
AB: The statistical relationship between the daily 1-hr maximum ozone concentrations and the daily maximum upper air temperature was explored for California's two most heavily polluted air basins: the South Coast Air Basin (SoCAB) and the San Joaquin Valley (SJV). The temperature at an elevation of 850-milibar pressure (T850) for the period 1980 – 2004 was obtained from the National Center for Environmental Prediction (NCEP) / National Center for Atmospheric Research (NCAR) Reanalysis1 dataset for Riverside (SoCAB) and Fresno (SJV). Daily 1- hr maximum ozone concentrations were provided by the California Air Resources Board (CARB) for Upland (SoCAB) and Parlier (SJV) for the same time period. The ozone concentrations at any given value of T850 were approximately normally distributed. The 25%, 50%, and 75% quartile ozone concentrations increased linearly with T850, reflecting the effect of temperature on emissions and chemical reaction rates. A 2-D Lagrangian (trajectory) form of the UCD/CIT photochemical air quality model was used to explain the standard deviation of the ozone concentrations at each value of T850. Three-day back trajectories were calculated for a typical air quality episode. The base case trajectory routes were then perturbed by adding stochastic bias to the wind-field. Temperature, relative humidity, mixing height, initial concentrations for VOC concentrations, background ozone concentrations, time of year and overall emissions were also perturbed in a realistic fashion during this study. A total of 62 model simulations were performed and the results were analyzed to show that long term changes to emissions inventories were the largest sources of ozone variability at a fixed value of T850. Projections of future T850 values in California were obtained from the Geophysical Fluid Dynamics Laboratory (GFDL) model under the Intergovernmental Panel on Climate Change (IPCC) A2 and B1 emissions scenarios for the years from 2001 to 2100. The future temperature trends combined with the historical statistical relationships suggest that the number of days with O3>90 ppb would increase by 0.5-0.7 days/year under the A2 emissions scenario and 0.2- 0.3 days/year under the B1 emissions scenario (assuming the emissions remained at 1990-2004 levels). These calculations help to quantify the climate "penalty" that must be overcome to improve air quality in California.
DE: 0325 Evolution of the atmosphere (1610, 8125)
DE: 0345 Pollution: urban and regional (0305, 0478, 4251)
SC: Atmospheric Sciences [A]
MN: 2007 Fall Meeting