Impact of the 2011 Southern US Drought on Ground-Level Particulate Matters (PM) in Summertime and Implication for Drought-Driven PM Response in Future Climate

Thursday, 18 December 2014
Yuanyu Xie1, Yuxuan Wang2, Wenhao Dong1, Qianqian Zhang3, Libao Chai1 and Lin Zhang4, (1)Center for Earth System Science, Tsinghua University, Beijing, China, (2)Texas A & M University, College Station, TX, United States, (3)Tsinghua University, Beijing, China, (4)Peking University, Beijing, China
Drought has wide spread influence over the continental US. Climate predictions suggest increasing frequencies and intensity in droughts, particularly over the southern and western US. In this study, we first present a quantitative assessment of the impacts of the 2011 Southern US drought on the distribution and budget of surface PM2.5 in the summertime using observations and the GEOS-Chem model. Through quantifying the complex dependence of PM2.5 species to meteorology parameters, we find different responses of OC and sulfate to drought conditions. There is an average enhancement of 26% (p < 10-4) in total PM2.5 over the southern US region during the drought, which is largely attributed to OC enhancements driven by increased emissions from wildfires and trans-boundary inflow from Mexico. By contrast, over central and eastern Texas, surface PM2.5 shows a mean decrease of 11% driven by a 26% (p < 0.03) reduction in sulfate due to decreased aqueous-phase oxidation. On the basis of our PM2.5 budget analysis of this drought event, a statistical approach is developed to estimate the impacts of similar droughts on PM2.5 air quality in the past decades and validated. Finally, we will apply the statistical relationship to discuss the implications on PM air quality of future changes in drought projected by climate models.