Atmospheric circulation and dynamic mechanism for persistent haze events in the Beijing–Tianjin–Hebei region

• DOI: 10.1007/s00376-016-6158-z
• Publication Date: 2017-02-28T14:19:50Z
• Authors: Ping Wu; Yihui Ding; Yanju Liu
• Keywords: Atmospheric Circulation; Haze; Westerlies

In this study, regional persistent haze events (RPHEs) in the Beijing–Tianjin–Hebei (BTH) region were identified based on Objective Identification Technique for Regional Extreme Events period 1980–2013. The formation mechanisms of severe RPHEs investigated with focus atmospheric circulation and dynamic mechanisms. Results indicated that: (1) 49 occurred during past 34 years. (2) could be categorized into two types according to large-scale circulation, i.e. zonal westerly airflow (ZWA) type high-pressure ridge (HPR) type. When ZWA-type occurred, BTH was controlled by near mid–upper troposphere. Southwesterly winds prevailed lower troposphere, near-surface wind speeds only 1–2 m s−1. Warm humid air originating from northwestern Pacific transported region, where relative humidity 70% 80%, creating favorable moisture conditions. HPR-type appeared, northwesterly troposphere region. Westerly conditions relatively weak. (3) Descending motion mid-lower caused above provided a crucial mechanism RPHEs. descending contributed reduction height planetary boundary layer (PBL), which generated an inversion This trapped abundant pollution PBL, leading high concentrations pollutants.