Meteorological characteristics associated with PM2.5 air pollution in Cleveland, Ohio, during the 2009–2010 Cleveland Multiple Air Pollutants Study

Cleveland, Akron, and Lorain, Ohio, exceed the National Ambient Air Quality Standards (NAAQS) for particles with a diameter less than 2.5 microns (PM2.5). The 2009–2010 Cleveland Multiple Air Pollutants Study (CMAPS) and analyses were conducted to characterize the sources and processes that contribute to high PM2.5 concentrations in the Cleveland area. The results are being used in high-resolution mesoscale chemical and meteorological modeling to protect public health. This paper summarizes the meteorological measurements collected during CMAPS and describes how three-dimensional meteorological processes influence surface PM2.5 concentrations. Mixing heights were higher, boundary layer winds were stronger, flow was southerly, and ventilation was greater on most episode days compared to non-episode days. While greater ventilation typically results in lower PM2.5 concentrations, in this case the greater ventilation coincided with the transport of regional pollution by southerly winds. Stagnation, or limited transport of air parcels, occurred on the remaining episode days and was associated with limited vertical mixing and light winds. These stagnation/limited dispersion events were associated with a weak lake breeze during the summer and slow-moving, large-scale high-pressure systems with weak surface pressure gradients, resulting in light winds during the winter.