Predicted impacts of climate and land-use change on surface ozone in the Houston, Texas, area

This paper studies the effects of climate change under future A1B scenario and land use change on surface ozone (O₃) in the greater Houston, Texas, area. We applied the Weather Research and Forecasting Model with Chemistry (WRF/Chem) to the Houston area for August of current (2001-2003) and future (2051-2053) years. The model was forced by downscaled 6-hourly Community Climate System Model (CCSM) version 3 outputs. High-resolution current year land use data from National Land Cover Database (NLCDF) and future year land use distribution based on projected population density for the Houston area were used in the WRF/Chem model coupled with an Urban Canopy Model (UCM). Our simulations show that there is generally a 2°C increase in near-surface temperature over much of the modeling domain due to future climate and land use changes. In the urban area, the effect of climate change alone accounts for an increase of 2.6 ppb in daily maximum 8-h O₃ concentrations, and a 62% increase of urban land use area exerts more influence than does climate change. The combined effect of the two factors on O₃ concentrations can be up to 6.2 ppb. The impacts of climate and land use change on O₃ concentrations differ across the various areas of the domain. The increase in extreme O₃ days can be up to 4-5 days in August, in which land use contributes to 2-3 days' increase. Additional sensitivity experiments show that the effect of future anthropogenic emissions change is on the same order of those induced by climate and land use change on extreme O₃ days.