2013年1月安徽持续性霾天气成因分析

Analyses on the Causes of the Persistent Haze in Anhui Province in January 2013

2013年1月安徽霾天气具有范围广、持续时间长、能见度低等特点。利用合肥、安庆、阜阳2009～2013年1月地面常规资料、高分辨率探空资料，结合轨迹分析和聚类分析，讨论了2013年1月安徽霾天气频发的原因。结果表明：低风速、高湿度不能解释2013年1月霾天气增多、增强的现象。大气层结稳定、接地逆温偏多、偏厚，可部分解释这次霾天气增多现象。边界层中上部输送条件的变化也不能解释2013年1月霾天气增多现象，但近地层输送条件的变化能较好地解释2013年1月霾天气增多现象，如偏东北来向的轨迹组对应着最低的能见度，且2013年1月各地最低能见度对应的轨迹组所占比例（或与次低能见度的轨迹组所占比例之和）在历年中最高。因此，大气层结稳定、近地层偏东北来向气团较多是2013年1月安徽各地能见度偏低、霾天气偏多的主要原因。

During January 2013, Anhui Province experienced frequent and severe haze, which was characterized as widespread and long-lasting with very low visibility. The potential causes of this long-lasting haze are discussed by using the routine daily ground level observational data of three representative stations and high space-resolution sounding data recorded at two stations in January of the most recent five years, together with trajectory-cluster-statistics analysis. The statistics show that low wind speed and high humidity alone cannot explain the low visibility and abundant haze, which reached historical levels in January 2013. The more frequent and deeper ground inversion, and thus, higher stability of stratification occurring at that time can partly explain these situations. Although the back-trajectories of the air mass at the height of 1 km cannot explain the severe haze in Anhui Province, those at the height of 100 m can sufficiently explain these situations. At the height of 100 m, the northeasterly trajectories corresponded to the lowest average visibility at all three stations. In January 2013, the frequency of trajectories corresponding to the lowest visibility group, or together with the second-lowest group, was the highest among the same period of the most recent five years. Therefore, the main reasons of the low visibility and high haze frequency in Anhui Province in January 2013 were more stable stratification and more controlling air masses from northeast.