The Impacts of Different PBL Schemes on the Simulation of PM2.5during Severe Haze Episodes in the Jing-Jin-Ji Region and Its Surroundings in China

Abstract

In this study, three schemes [Yonsei University (YSU), Mellor-Yamada-Janjic (MYJ), and Bougeault-Lacarrère (Boulac)] were employed in the Weather Research and Forecasting/Chemistry (WRF-Chem) model to simulate the severe haze that occurred in February 2014 in the Jing-Jin-Ji region and its surroundings. The PM2.5concentration simulated using the three schemes, together with the meteorological factors closely related to PM2.5(wind speed, local vertical diffusivity, and PBL height), was evaluated through comparison with observations. The results indicated that the eastern plain cities produced better simulation results than the western cities, and the cities under the eastern root of Taihang Mountain produced the worst results in simulating high PM2.5concentration in haze. All three schemes simulated very similar variation trends of the surface PM2.5concentration compared with observations. The diurnal variations of simulated surface PM2.5were not as reasonable as their reflection of daily averaged variation. The simulated concentrations of surface PM2.5using the YSU, MYJ, and Boulac schemes all showed large negative errors during daytime in polluted days due to their inefficient descriptions of local atmospheric stability or diffusion processes in haze. The lower ability of PBL schemes in distinguishing the diffusion between haze and clean days in the complex topography areas in China is an important problem for PM2.5forecasting, which is worthy of being studied in detail.