Simulation of continental U.S. air quality on climatic time scales: projection in future climate

Ho-Chun Huang

Potential global warming could lead to deteriorating air quality in the future. To study air quality problems, a mesoscale meteorological model that integrates all available observed data often is used to mimic the most realistic weather systems in the present climate. For future regional climate projection, a regional climate model (RCM) that can integrate the information of GCM simulations for future climate conditions is used. The projected future air quality contains a wide range of uncertainty resulting from, for example, the driving GCM simulations, emission scenarios, and numerical schemes implemented in the RCM and air quality model (AQM). The National Centers for Environmental Prediction-Department of Energy (DOE) global reanalysis data (R2) was used to drive the RCM meteorology for AQM simulations representing the present climate. The results of model evaluation show that the regional climate modeling system has skill in projecting the future air quality in the Northeast, Midwest, and Texas subdomains. The U.S. DOE Parallel Climate Model (PCM) simulations were used to drive AQM simulations for the present climate (1996-2000) for baseline statistics as well as AQM simulations for a future climate (2048-2052). To obtain the range of uncertainty in future air quality projection, two RCM cumulus schemes (Grell and Kain-Fritsch) and two IPCC emission scenarios (A1Fi and B1) were used. The results, using 30km grid resolution data, show that the changes of daily average ozone concentration from present climate to future climate ranged from -10.80% in the Northeast subdomain to 14.06% in the Midwest. The results also indicate significant changes in the Southeast ranging from -12.42% to 22.58% (using 90km grid resolution data).