Aerosol Particle Size Distribution (0.1–1.0μm) during the Chinooks of 1979 over Calgary, Canada

Abstract

During the winter months of 1979, an Active Scattering Aerosol Spectrometer was operated in down-town Calgary to measure the effect of chinooks on the aerosol particle size distribution in the range 0.1–1.0 μm. An Aerovironment Acoustic Sounder provided information on the stability of the lower atmosphere and the onset of chinooks, while an Integrating Nephelometer continuously monitored the atmospheric aerosol volume scattering coefficient yielding information on the optically active suspended particulates. Contrary to the conclusions of an Alberta Environment Report, this study shows that chinook events are accompanied by higher air pollution and that the concentration of particles with radii in the neighborhood of 0.1 μm increases dramatically, while that of particles of larger radii shows only a moderate increase. Strong temperature inversions, which are always associated with chinooks, are times of air stagnation and higher concentration of particles of all sizes resulting in poor visibility conditions and possibly posing a health hazard. But as the inversion terminates, that is, when the chinook reaches ground level, the clean mountain air replaces the highly polluted city air and the particle size distribution returns to normal background level.