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Extremely severe and persistent haze occurred in January 2013 over easternand northern China. The record-breaking high concentrations of fineparticulate matter (PM2.5) of more than 700 μg m−3 onhourly average and the persistence of the episodes have raised widespread,considerable public concerns. During that period, 7 of the top 10 pollutedcities in China were within the Hebei Province. The three cities in southernHebei (Shijiazhuang, Xingtai, and Handan) have been listed as the top threepolluted cities according to the statistics for the first half of the year2013. In this study, the Mesoscale Modeling System Generation 5 (MM5) and theModels-3/Community Multiscale Air Quality (CMAQ) modeling system are appliedto simulate the 2013 severe winter regional hazes in East Asia and northernChina at horizontal grid resolutions of 36 and 12 km, respectively, usingthe Multi-resolution Emission Inventory for China (MEIC). The sourcecontributions of major source regions and sectors to PM2.5concentrations in the three most polluted cities in southern Hebei arequantified by aiming at the understanding of the sources of the severe hazepollution in this region, and the results are compared with December 2007,the haziest month in the period 2001–2010. Model evaluation againstmeteorological and air quality observations indicates an overall acceptableperformance and the model tends to underpredict PM2.5 and coarseparticulate matter (PM10) concentrations during the extremely pollutedepisodes. The MEIC inventory is proven to be a good estimation in terms oftotal emissions of cities but uncertainties exist in the spatial allocationsof emissions into fine grid resolutions within cities. The sourceapportionment shows that emissions from northern Hebei and theBeijing-Tianjin city cluster are two major regional contributors to thepollution in January 2013 in Shijiazhuang, compared with those from Shanxiand northern Hebei for December 2007. For Xingtai and Handan, the emissionsfrom northern Hebei and Henan are important. The industrial and domesticsources are the most significant local contributors, and the domestic andagricultural emissions from Shandong and Henan are non-negligible regionalsources, especially for Xingtai and Handan. Even in the top two haziestmonths (i.e., January 2013 and December 2007), a large fraction of PM2.5in the three cities may originate from quite different regional sources.These results indicate the importance of establishing a regional jointframework of policymaking and action system to effectively mitigate airpollution in this area, not only over the Beijing-Tianjin-Hebei area, butalso surrounding provinces such as Henan, Shandong, and Shanxi

The 2013 severe haze over southern Hebei, China: model evaluation, source apportionment, and policy implications