Planetary boundary layer height determination during Pacific 2001 using the advantage of a scanning lidar instrument

A novel method for determining the boundary layer height has been developed specifically for scanning lidar data. The Meteorological Service of Canada has recently developed a scanning lidar facility (RASCAL—Rapid Acquisition Scanning Aerosol Lidar) capable of fast azimuth and elevation scanning profiles of the lower troposphere. During the Pacific 2001 field campaign in the Lower Fraser Valley (LFV) of British Columbia, RASCAL measurements were conducted from the Langley Lochiel ground site (49.03°N, 122.60°W). Dependent on weather, measurements were made for approximately 16 h per day between 14 and 30, August 2001, to measure the early morning boundary layer growth and its collapse to the nocturnal boundary layer. The instrument was set-up to make continuous elevation scans at three different azimuths representing the “West”, “North” and “East” direction. A robust boundary layer height algorithm has been developed to exploit the advantages of high-resolution scanning lidar data. On certain days, substantial differences in boundary layer height are evident between the different directional scans. Results also show a consistent “breakdown” of the boundary layer at approximately 19:00 PDT visible on almost every day that measurements were obtained. Accurate determination of the boundary layer is a critical parameter in understanding the regional air quality within the LFV.