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Abstract：
Rapid development has led to frequent haze in Beijing. With mountains and sea surrounding Beijing, the pollution is found to be influenced by the mountain-plain breeze and sea-land breeze in complex ways. Meanwhile, the presence of aerosols may affect the surface energy balance and impact these boundary layer (BL) processes. The effects of BL processes on aerosol pollution and the feedback between aerosol and BL processes are not yet clearly understood. Thus, the Weather Research and Forecasting model coupled with Chemistry (WRF-Chem) is used to investigate the possible effects and feedbacks during a haze episode on 23 September 2011. Influenced by the onshore prevailing wind, sea-breeze, and upslope breeze, about 45% of surface particulate matter (PM)2.5 in Beijing are found to be contributed by its neighbor cities through regional transport. In the afternoon, the development of upslope breeze suppresses the growth of BL in Beijing by imposing a relatively low thermal stable layer above the BL, which exacerbates the pollution. Two kinds of feedback during the daytime are revealed as follows: (1) as the aerosols absorb and scatter the solar radiation, the surface net radiation and sensible heat flux are decreased, while BL temperature is increased, resulting in a more stable and shallower BL, which leads to a higher surface PM2.5 concentration in the morning and (2) in the afternoon, as the presence of aerosols increases the BL temperature over plains, the upslope breeze is weakened, and the boundary layer height (BLH) over Beijing is heightened, resulting in the decrease of the surface PM2.5 concentration there.
摘要：
快速发展导致北京雾霾频发。北京周围有山脉和大海，发现污染以复杂的方式受到高山微风和海陆风的影响。同时,气溶胶的存在可能会影响表面能量平衡并影响这些边界层（BL）过程。尚不清楚BL过程对气溶胶污染的影响以及气溶胶与BL过程之间的反馈。因此，天气研究和预测模型与化学（WRF-Chem）结合用于调查2011年9月23日雾霾事件期间可能的影响和反馈。受陆上盛行风的影响，海风,和上坡的微风，北京约有45％的表面颗粒物（PM）2.5是通过区域运输由其邻近城市贡献的。在下午,上坡微风的发展通过在BL上方施加相对较低的热稳定层抑制了BL在北京的生长，这加剧了污染。揭示了白天的两种反馈：（1）由于气溶胶吸收和散射太阳辐射，表面净辐射和显热通量降低，当BL温度升高时，导致更稳定、更浅的BL，这导致了较高的表面PM2.5浓度在上午和（2）在下午，由于气溶胶的存在增加了平原上的BL温度，上坡的微风减弱，北京上空边界层高度(BLH)升高，导致地表PM2.5浓度下降。
