Enhanced aerosol-radiation interaction effects due to altered entrainment rates in the boundary layer

Entrainment is crucial to the development of the atmospheric boundary layer, and in turn modulates the exchanges of heat, momentum, and pollutants between the boundary layer and the free atmosphere. Aerosol-radiation interaction (ARI) is expected to weaken the entrainment process and flux rates in the boundary layer, however, present boundary layer mixing schemes in air quality models generally do not account for this feedback. In this study, we will first evaluate the responses of boundary layer meteorology and air pollution concentrations to altered entrainment flux rates due to ARI using a prescribed value calculated by large eddy simulations (LBS) study. We apply the modified entrainment rate scheme in the WRF-Chem model to analyze PM_2.5 pollution over North China. Our results show that decreased entrainment rates can lead to reduced boundary layer height, suppressed surface wind speed, enhanced boundary layer stability, and intensified air pollution in BTH region. Episodic-mean surface PM_2.5 concentration could increase up to 20 ug/m3 in urban Beijing during January 2015, which indicates current air quality models might underestimate the perturbations of meteorology and chemistry due to ARI. A LBS-evaluated scheme to online calculate convection-radiation dependent entrainment rates is also being implemented in the WRF-Chem model and will be presented.