A rapid increase in the PM_2.5 concentration in Beijing, China, on 30 November 2015 was found to be transported from south of Beijing by both turbulent mixing and advection processes. The nighttime relatively clean air was from the downslope flow northwest of Beijing; the rapid increase in the PM_2.5 concentration in the morning resulted from the downward convective turbulent transfer of the polluted air that was rapidly advected over the nighttime stable boundary layer.