Air mass characterization at the Whistler Mountain air chemistry site

Mountaintop air chemistry observatories constitute an important component of the limited observing network for studying long-range transport of atmospheric pollution. An air chemistry site operated by Environment Canada on the summit of Whistler Mountain, British Columbia (2182 m) is one of only a few such observatories in western North America that have been established primarily to detect and quantify trans-Pacific transport of Asian-sourced pollutants. A study of the local mountain meteorology of Whistler is being conducted to determine when this site is influenced by boundary layer air from the lowlands, which may contain local pollution. Criteria are being developed to distinguish periods of boundary layer influence from those that are representative of the free troposphere. This research has been enabled by the recent installation of a dense network of meteorological sensors on and near Whistler Mountain related to forecasting efforts for the 2010 Winter Olympics. The unique dataset available from Whistler allows for a multi-faceted observational study to determine what parameters best characterize the mountaintop air masses. Mechanisms for diurnal boundary layer growth and thermally induced slope flows are being investigated through analysis of data from weather stations at various elevations on the mountain. The diurnal cycles of water vapor and aerosol parameters are being evaluated as possible indicators of boundary layer influence on the peak. Vertical profiles of temperature and water vapor from a microwave profiling radiometer are also being analyzed to assess the potential for this instrument to provide a means of tracking temporal changes in the mixed-layer depth. Results from this study are expected to aid in the interpretation of air chemistry data collected at the Whistler observatory, adding confidence to researchers' conclusions about the effects of long-range transport on the regional air quality of the Pacific Northwest.