Characteristics of particulate matter and meteorological conditions of a typical air-pollution episode in Shenyang, northeastern China, in winter 2017

Northeastern China (NEC) has experienced serious environmental problems by energy consumption and domestic emission. This paper reviews an extreme haze event occurred in Shenyang, NEC, on 5-9 January 2017. The meteorological data, extinction coefficients from ground-based Lidar and aerosol optical products from Moderate Resolution Imaging Spectroradiometer (MODIS) were used to study this pollution evolution. The deterioration of visibility lasted for 57 h with a minimum value reached to 0.2 km. The SO2 decreased slightly to approximately 150 mu g/m(3) while the NO2 mass concentration increased to approximately 100 mu g/m(3). The northeastern wind (1-2 m/s) and higher relative humidity (RH) (90%) as well as increased pressure (1020 hPa) were conducive to particulate matter (PM) accumulation and degraded visibility. An inversion layer began to appear at 0.2 km and developed upward to 2.0 km with the development of heavy pollution, and the RH in the ground and upper air both increased significantly to 80%-90% to conducive larger aerosol extinction. The aerosol extinction coefficient increased to 1.7-1.8 km(-1) during the serious pollution, and the average aerosol optical depth (AOD) increased to 1.5 with a larger angstrom ngstrom exponent (AE) increasing to 1.5 on 7 January. Five main clusters of air trajectories indicated that pollutants from the northwest, southwest, and local emissions affected Shenyang. These findings elucidate the coordinated variation in visibility, PM, and meteorology elements in the near and upper surfaces as well as the spatial distribution in aerosols from satellites during the special pollution episode in NEC.