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A heavy fog-haze episode occurred over North China Plain during the period from 11 to 14 January 2013 with the continuous 4-day’ air pollution index (API) ranging from 300~500 reported by Ministry of Environmental Protection of China.The Weather Research and Forecasting (WRF)-Chem model was applied to simulate the temporal and spatial distribution features of air pollutants during this fog-haze episode.Comparing with observations,model can reasonably predict the temporal and spatial variation of gaseous pollutants (e.g.,SO2,NOX),PM2.5,aerosol optical depth and extinction coefficient based on the reproduced metrological conditions (temperature,relative humidity (RH),wind and precipitation) in January 2013 over North China Plain.The model results showed that during 11-14 January,the high PM2.5 was over southeast part of Beijing,south and east part of Hebei province with the highest daily average value ranging from 400~500 μg m-3.The analysis of the historical climate data (1951~2013) indicated large positive anomaly (+20%~40%) of RH and negative anomaly (~-1 m s-1) of wind speed during the period from 11-14 January.The sounding data also showed that there are temperature-inversion layers with the difference at ~5℃ and high RH maintained at 80~90% under 1km from 11 to 13 January over Beijing.Such metrological conditions were favor for the hygroscopic growth and accumulation of aerosols.The model results showed that from 11 to 14 January,the water vapor was transported with southerly wind over the near-surface layer and the dust aerosol was transported with northwesterly wind over the upper layer (850hPa) to North China Plain area which both contributed to the continuous high PM2.5 and fog-haze days there.