Impacts of regional climate change on biogenic emissions and air quality

[1] Regional air quality simulations are conducted at a horizontal grid resolution of 36 km for four summers (2001, 2002, 2051, and 2052) to examine the sensitivity of air quality to potential regional climate change in the United States. In response to the predicted warmer climate in 2051/2052, the emissions of isoprene and terpene increase by 20-92% and 20-56%, respectively, over most of the domain. Surface O-3 increases by up to 19-20%. Such increases are largely driven by changes in temperature, solar radiation, and cloud fraction over most of the domain. PM2.5, its compositions, and visibility exhibit an overall negative sensitivity (decrease by up to 40%), resulting from the competition of the negative temperature effect and positive emission/temperature effects. While the response of dry deposition is governed by the negative sensitivity of surface resistances, that of wet deposition is either positive or negative, depending on the relative dominancy of changes in PM2.5 and precipitation. Overall the net climatic effect due to changes in climatic variables alone dominates changes in O-3, PM2.5, and wet and total deposition, and the net biogenic emission effect due to changes in biogenic emissions alone as a result of climate change is important for isoprene, organic matter, visibility, and dry deposition over several regions. Models that do not include secondary organic aerosol formation from isoprene may underestimate by at least 20% of the responses of organic aerosols to future climate changes over many areas of the modeling domain. Both regional climate and air quality exhibit interannual variability, particularly in temperature, isoprene emissions, and PM2.5 concentrations, indicating a need for long-term simulations to predict future air quality. Compared with results from global models, stronger regional climate change signals may cause projected local impacts of climate change that are stronger or even different in sign.