North China Plain (NCP) is one of the most of heavily polluted regions in the world, air pollution associated with haze threatens human health. A high PM_2.5 concentration event in the NCP from 30 November to 10 December 2017 was simulated and analyzed by using the Weather Research and Forecasting (WRF) model and the Nested Air Quality Prediction Modeling System (NAQPMS) with an integrated analysis tool coupling source apportionment with process analysis. The weather field simulated by the WRF model and the PM_2.5 concentration simulated by NAQPMS agreed well with observations, and the correlation coefficient of PM_2.5 between the simulation and observation data remained >0.8 during the study period. We found that this high PM_2.5 event can be divided into three phases in NCP: The accumulation of PM_2.5 in Phase I was slow and dominated by south or weak winds in the stable boundary layer. In Phase II, PM_2.5 concentrations kept a high value in the short term under northern winds resulting from the edge of a cold front. The sustainable high value of PM_2.5 concentration in the middle and south of the NCP under northly wind has been less reported. An integrated process contribution analysis and source apportionment technology coupled with NAQPMS showed that the PM_2.5 in the north and middle of the NCP were transported to the southern area by the horizontal transmission process. This transport kept PM_2.5 high in the south of the NCP and even exceeded the contribution of local emissions. In the Phase III, the strong northern winds from main body of the cold front brought clear air masses and caused the PM_2.5 decrease in the whole NCP. The study shows that high dense emissions in the middle of NCP are the main cause for the high PM_2.5 events in the whole region, and the north wind could transport the pollutants form upstream region to downstream region, causing the continued high PM_2.5 in the middle and south of NCP.

华北平原（NCP）是世界上污染最严重的地区之一，与霾相关的空气污染威胁着人类健康。使用天气研究和预报（WRF）模型和嵌套空气质量预测建模系统（NAQPMS）和集成的分析工具，结合源解析，对2017年11月30日至12月10日的NCP中PM _2.5浓度高的事件进行了模拟和分析与过程分析。WRF模型模拟的天气场和NAQPMS模拟的PM _2.5浓度与观测值吻合得很好，在研究期间模拟与观测数据之间的PM _2.5相关系数保持> 0.8。我们发现这个高PM _2.5NCP事件可分为三个阶段：第一阶段的PM _2.5积累缓慢，且在稳定边界层受南风或弱风的控制。在第二阶段，由于冷锋的边缘，在北风下，PM _2.5浓度在短期内保持较高的值。在北风的作用下，NCP中南部PM _2.5浓度的可持续高值报道较少。综合的过程贡献分析和源分配技术与NAQPMS结合显示，NCP北部和中部的PM _2.5通过水平传输过程被输送到南部地区。这种运输保持了PM _2.5在NCP南部很高，甚至超过了局部排放的贡献。在第三阶段，来自冷锋主体的强北风带来了清晰的气团，并导致整个NCP的PM _2.5下降。研究表明，北卡罗来纳州中部高密度排放是造成整个地区PM _2.5高事件的主要原因，而北风可能将污染物从上游地区输送到下游地区，从而导致该地区PM _2.5持续较高。 NCP的中南部。