The intensification of wildland fires across portions of Canada in early June 2023 led to significant smoke transport into the eastern United States, resulting in poor air quality and reduced visibility. Significant degradation of air quality was evident from PM2.5 surface measurements along the smoke plume as it moved southwards, which was confirmed by satellite data and the operational HRRR-Smoke model. The availability of Doppler lidar data and the publicity surrounding the poor conditions in Washington DC led to a focused effort addressing the timing and enhancement of smoke in the nation's capital. The predictive skill of the operational HRRR-Smoke model was evaluated against wind profile and PM2.5 surface measurements. In general, the HRRR-Smoke forecast accurately predicted the meteorological conditions, particularly the diurnal evolution of regional winds and boundary layer depth. Despite capturing the diurnal evolution of winds, errors were still seen in the wind shear structure and magnitude (biases ranged between ± 2 m s-1and ± 4 m s-1). In terms of air quality, good agreement was found between modeled and observed PM2.5 concentrations at four sites in Washington DC. Confidence in modeled winds and PM2.5 allowed HRRR-Smoke to be used to determine the development of a lee trough as a regional transport mechanism for circulating smoke into Washington DC and leading to bad air quality.
Pichugina et al. (Tue,) studied this question.