Meteorological analysis of the Pacific 2001 air quality field study

A detailed analysis is provided for the meteorological conditions that prevailed during the Pacific 2001 Air Quality Field Study (13–31 August 2001). The general region of interest is the Georgia Basin with a focus on the Lower Fraser Valley of British Columbia. The study period can be broken into three distinct periods: dry, wet and unsettled. Particular attention is paid to synoptic scale conditions, low-level flow, back trajectory analyses and stability conditions associated with the dry and unsettled periods. A pressure slope index, based on sea-level pressure, was developed to characterise the sea breeze–land breeze signal. This index proved useful in describing the low-level flow over the valley for time resolutions on the order of one hour. Indeed, the index highlighted two periods where a prominent sea breeze–land breeze cycle had prevailed. Back trajectory output from multiple models along with observed winds provided a detailed description of pollutant source regions and the flow pattern in the lower troposphere during the field study. Finally, approaches to calculating the mixing height based on radiosonde data were introduced. The spatial and temporal variability of this data combined with the flow diagnosis illustrated the relationship between the mixing height and the sea breeze–land breeze cycle.