REVEAL II: Seasonality and spatial variability of particle and visibility conditions in the Fraser Valley

This paper presents data collected during a year-long field experiment REVEAL II. in the Fraser Valley, British Columbia. The data are used to provide information regarding ambient visibility conditions and fine particle concentrations in the valley. Although average fine mass measured during REVEAL II was 8]9 mg my3, the fine particle mass has high light-scattering efficiencies and the visual range is frequently below publicly defined acceptable levels. For example, data indicate that during the fall the visual range is frequently below 20 km even under favorable meteorological conditions. Source apportionment analyses of mass and particle light-scattering indicate motor vehicles may contribute as much as 40% of the fine particle mass in the central valley and up to one-third of the particle light-scattering. In addition to characterizing conditions in the Fraser Valley, slides taken at a number of sites during REVEAL II are used to evaluate a simple method for obtaining classed. quantitative estimates of visual range from this medium without requiring access to specialized instrumentation.