The vertical chemical and meteorological structure of the boundary layer in the Lower Fraser Valley during Pacific ʹ93

Mixed layer depths were derived from potential temperature profiles from aircraft, high-altitude balloon sonde and tethersonde measurements taken during the Pacific ʹ93 field study in the Lower Fraser Valley of southern British Columbia. In general, mixed layer depths derived from these different data sources were closely comparable. An airborne lidar was used to map aerosol depth throughout the valley. These lidar-derived aerosol depths compared well with the meteorologically derived mixed layer depths. During one notable ozone episode, mixed layer depths were low, and in the range 500–800m. Measurements of chemical pollutants such as ozone and nitrogen oxides showed these to be generally well mixed below the top of the mixed layer during daytime. However, at times, layering within and above the inversion layer was observed.