Meteorology Associated with Cool Season PM2.5 Pollution Episodes in Portland, Oregon

Abstract:

Situated in the Willamette Valley, Portland, Oregon is prone to episodes of high concentrations of PM2.5 during the residential wood burning season (October-February). Local and synoptic meteorology of the area, including wind patterns, temperature, and atmospheric stability contribute to these high PM2.5 concentrations. In order to better predict days with unhealthy concentrations of PM2.5 during the winter wood burning season, here we characterize the meteorological conditions that have historically been associated with poor air quality in the city. Local and regional scale wind, pressure, and temperature patterns are identified for days with high concentrations of PM2.5, as identified by an urban central site monitor. Additionally, measures of atmospheric stability and airmass stagnation are constructed and associated with PM2.5 concentrations. Results suggest synoptic patterns that are favorable for episodes of poor air quality include broad areas of high pressure both aloft and at the surface, weak horizontal low-level pressure gradients, and conditions idea for efficient nighttime radiative cooling. By identifying these large-scale and local weather patterns and meteorology conducive to high concentrations of PM2.5 will help improve forecasts of air pollution events and facilitate approaches to limit air pollution in the Portland Metro area.