Boundary Layer Height Retrievals in Wildfire Smoke Over Chicago Using a Multi-Instrument Approach

Measuring the height of the planetary boundary layer (PBL) is key to estimating mass fluxes, and thus a variety of other important meteorological parameters, such as wind, temperature, and humidity. However, in conditions with smoke aloft in the atmosphere, the height of the PBL is often difficult to measure. In this project, a scanning Doppler LiDAR and a dual polarization Vaisala CL-61 ceilometer were deployed on the rooftop of the BBH building of Northeastern Illinois University in Chicago as a part of the Community Research on Climate and Urban Science (CROCUS) project. We applied Haar wavelet analysis techniques and other image processing methods to retrieve the planetary boundary layer height (PBLH) during June 2023 when Canadian wildfire smoke was present over Chicago. We conclude that the capability of the Doppler LiDAR in vertically staring mode to retrieve vertical radial velocities enables it to produce a boundary layer profile that matches the expected diurnal cycle of the PBL, retrieving PBLH much more effectively than the CL-61 during these wildfire smoke events.