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Recent advances in the development of large eddy simulation (LES) atmospheric models with corresponding atmospheric transport and dispersion (AT&D) modeling capabilities have made it possible to simulate short, time-averaged, single realizations of pollutant dispersion at the spatial and temporal resolution necessary for common atmospheric dispersion needs, such as designing air sampling networks, assessing pollutant sensor system performance, and characterizing the impact of airborne materials on human health. The high computational burden required to form an ensemble of single-realization dispersion solutions using an LES and coupled AT&D model has, until recently, limited its use to a few proof-of-concept studies. An example of an LES model that can meet the temporal and spatial resolution and computational requirements of these applications is the joint outdoor-indoor urban large eddy simulation (JOULES). A key enabling element within JOULES is the computationally efficient graphics processing unit (GPU)-based LES, which is on the order of 150 times faster than if the LES contaminant dispersion simulations were executed on a central processing unit (CPU) computing platform. JOULES is capable of resolving the turbulence components at a suitable scale for both open terrain and urban landscapes, e.g., owing to varying environmental conditions and a diverse building topology. In this paper, we describe the JOULES modeling system, prior efforts to validate the accuracy of its meteorological simulations, and current results from an evaluation that uses ensembles of dispersion solutions for unstable, neutral, and stable static stability conditions in an open terrain environment.

The objective of this study was to calculate the prevalence of multiple exposures to four modifiable risk factors (smoking, alcohol, physical inactivity and overweight) and to establish whether there are more Canadians with multiple risk factor exposures than those with singular ones. Weighted estimates of the prevalence of mutually exclusive risk factor clusters were calculated according to the Canadian Community Health Survey, Cycle 1.1 (2000). Confidence limits were estimated by bootstrap techniques. Findings indicate that 21.0 percent of Canadians have no risk factor exposures, 53.5 percent are physically inactive, 21.5 percent currently smoke, 44.8 percent are overweight, and 6.0 percent are high-risk drinkers. Compared to females, males are less physically inactive but more likely to smoke, have high alcohol intake and be overweight, across all age groups. At least one risk factor was present in 79.0 percent of Canadians and 39.0 percent have at least two coexistent exposures. The distribution of risk factor prevalences differed significantly by age, most peaking among those between age 35 and 64, with the exception of physical inactivity. Those who smoke and are physically inactive account for the highest proportion of the population with two or more coexistent risk factors. Canadians who are free of the four risk factors for chronic disease examined in this paper constitute the minority. Future studies are recommended to examine other risk factors, as well as interactions of multiple exposures in association with chronic disease.