Assessment of Heat Stress and Associated Air Quality for Current and Future Climate in a Major Urban Area in the USA

We develop a modeling study to examine the complimentary effects of heat waves and air quality on human health in a major urban area in the US under current and future climate conditions. Current and future climate and air quality scenarios were simulated for the months of May, June, July, and August for two years, 2003 and 2050 using dynamical downscaling (108-36-12km). Large-scale meteorological conditions were based on Community Climate System Model (CCSM) simulations of those months during the specified years. Regional meteorological conditions were simulated by the Weather Research and Forecasting (WRF) model, and emissions were processed using the Sparse Matrix Operator Kernel Emissions (SMOKE) processor. The meteorological and emissions outputs were used by Community Multiscale Air Quality (CMAQ) model to simulate the predicted air quality parameters for each climate scenario.

We focus our analysis on the Chicago urban area in the USA. We used the wet bulb globe temperature (WBGT) to characterize heat stress, as a number of organizations around the world use it as a basic measure of heat stress (e.g., ISO 7243 heat stress standard). ISO 7243 is a heat stress index with thresholds relating directly to levels of physical activity. Using WBGT we identify heat waves episodes. We adopt the concept of Local Climate Zones (LCZs) (Stewart and Oke , 2012) to account for the considerable spatial variations in structural (sky view factor, building heights, aspect ratios etc.) and surface cover properties that contribute to the heat load within cities and which are not captured by regional scale models (12 km in this case). We examine the ambient air quality (ozone and PM2.5) patterns during the heat waves episodes under the two climate regimes to further assess potential exacerbated impacts on health.