Improving understanding of haze pollution In the North China Plain via atmospheric modeling and data assimilation

Frequent haze events have been happening in the North China Plain (NCP), and the severity of these events has attracted massive attention from both the public and the scientific community. Extremely high aerosol loadings in these haze events significantly influence visibility, human health and climate. Thus, improving understanding of haze pollution is of great importance. Furthermore, air quality modeling remains challenging.

This thesis elucidated the roles of meteorology, secondary aerosol formation, regional transport, and aerosol feedbacks in winter haze formation, clarified the impacts of emission changes and meteorology changes on PM2.5 concentrations, directly emphasized the importance of implementing pollution control strategies using assessments of health and climate effects, and improved model performance in simulating sulfate and PM2.5 via incorporating heterogeneous sulfate formation and assimilating surface PM2.5 concentrations. This thesis also provided some implications for policy makers. Priorities should be given to control SO2, NH3, and OC emissions, which can be achieved by promoting the shift from coal/biofuel to cleaner energy, and by changing animal feeding and housing ways. In addition, more attention to greenhouse gases and absorbing aerosols is still necessary since absorbing aerosols play important roles in aerosol feedbacks, aerosol feedbacks can aggravate haze pollution, and increases in temperature may increase aerosol concentrations. To protect the public health, it is of great importance to predict air pollution episodes, release alerts of incoming severe haze episodes, and take emergency measures to reduce pollution levels.