Impact of Chinooks on Calgary's air quality: Acoustic sounder observations of atmospheric stability

An atmospheric acoustic sounder was operated at the University of Calgary for the period March 1976 to July 1977. The stability of the atmospheric boundary layer has been determined from the acoustic chart records. Comparison of the seasonal cycle of stability with changes in the diurnal variation of NO _x , concentrations in Calgary's downtown core indicates that the sounder measurements are relevant to the air quality problem. It is shown that stability criteria derived from sounder records can stratify hourly pollutant concentration data. In addition, the sounder identifies a characteristic state of the urban boundary layer linked with Chinook winds. Evidence is presented that the probability of pollutant build-up in this layer is particularly high (～ 90%) when surface winds are less than 30 km h^?1 and from the south quadrant.