Air Quality, Circulation Patterns, and Long-range Transport
Exposure to ozone and fine particulate matter is a significant public health issue globally. To predict how pollution fluctuates at or near the surface, we need to understand both emissions and weather patterns. In a large-scale meteorological analysis specific to Texas, we found variations in the Bermuda High was the most important predictor of interannual variance of monthly mean ozone in Houston in summer [Wang et al., 2016]. The location and strength of the Bermuda High control whether or not low-ozone maritime air from the Gulf of Mexico can enter southeastern Texas and affect air quality. This mechanism also applies to other coastal urban regions along the Gulf Coast. However, under certain conditions the maritime air can be contaminated by pollutants originated from Central America. This happens predominantly in spring, the peak season of Central America biomass burning. We showed that long-range transport of those fire emissions can cause significant changes to the chemical composition of the otherwise clean maritime air masses flowing into southeastern Texas [Wang et al., in prep].
Interaction between Drought and Atmospheric Chemistry
Drought impact on agriculture and water resources is well established. However, the impact of increasing drought on air quality through both land and atmospheric processes is largely unexplored. We conducted a case study of the 2011 severe drought over Texas and the Southern Plains and found significant changes in surface PM2.5 during drought [Wang et al., 2015]. We then performed a comprehensive assessment of the impact of drought on US air quality, with a specific focus on ozone and PM2.5 [Wang et al., 2017]. Large enhancements of ozone (8%) and PM2.5 (17%) were found under drought conditions, indicating significant adverse effects of drought on air quality and hence human health. Those effects are largely attributed to natural processes, with the land biosphere and changing atmospheric conditions being major contributors. In addition to the air quality effect, we are exploring the extent to which drought-induced modifications in atmospheric compositions can present potentially large feedbacks to climate.
Pollution Chemistry, Emissions, and Climate Change in East Asia
East Asia is an important region experiencing a rapidly changing atmospheric environment whose underlying mechanisms and global impacts are poorly understood. To better represent dense source regions over East Asia in a global context, we have led the development of the nested-grid GEOS-Chem chemical transport model [Wang et al., 2004; Chen et al., 2009]. Through integrated modeling and observation analysis, our research has investigated the mechanisms of tropospheric ozone and aerosols formation over China and its megacities [Wang et al., 2009, 2013; Zhang et al., 2015], particularly the unique atmospheric chemistry of sulfate aerosols under severe winter haze conditions [Wang et al., 2014]. We also used the emerging in situ and satellite measurements to quantify Chinese emissions via the ‘top-down’ approach [Wang et al., 2007; 2010, 2013], and simulated the potential changes in response to future changes in both climate and emissions [Wang et al., 2010; Wang et al., 2013].