Abstract
Abstract. Vertical distributions of aerosol optical properties derived from measurements made during 11 aircraft flights over the North China Plain (NCP) in May–June 2016 during the Air Chemistry Research In Asia (ARIAs) were analyzed. Aerosol optical data from in situ aircraft measurements show good correlation with ground-based measurements. The regional variability of aerosol optical profiles such as aerosol scattering and backscattering, absorption, extinction, single scattering albedo (SSA), and the Ångström exponent (α) are thoroughly characterized for the first time over the NCP. The SSA at 550 nm showed a regional mean value of 0.85 ± 0.02 with moderate to strong absorption and the α ranged from 0.49 to 2.53 (median 1.53), indicating both mineral dust and accumulation-mode aerosols. Most of the aerosol particles were located in the lowest 2 km of the atmosphere. We describe three typical planetary boundary layer (PBL) scenarios and associated transport pathways as well as the correlation between aerosol scattering coefficients and relative humidity (RH). Aerosol scattering coefficients decreased slowly with height in the clean PBL condition, but decreased sharply above the PBL under polluted conditions, which showed a strong correlation (R2 ≥ 0.78) with ambient RH. Back-trajectory analysis shows that clean air masses generally originated from the distant northwestern part of China, while most of the polluted air masses were from the heavily polluted interior and coastal areas near the campaign region.
Highlights
Aerosol loading in eastern China has become exceptionally heavy and highly variable due to drastic increases in the emissions of pollutants during the last several decades
We present field measurements of the ambient aerosol extinction coefficient by using a CAPS instrument with a time resolution of 1 s at the Xingtai supersite
relative humidity (RH) is measured by a thin-film capacitance sensor, and its uncertainties and errors depend on temperature and global positioning system (GPS) location (Steinke et al, 2015)
Summary
Aerosol loading in eastern China has become exceptionally heavy and highly variable due to drastic increases in the emissions of pollutants during the last several decades. Generated local circulations can carry high concentrations of surface air pollutants and change the PBL structure (Chen et al, 2009) Such variable aerosol vertical distributions can alter the optical properties of aerosols such as AOD, affecting the regional radiation balance (Liu et al, 2012) and even the global radiative forcing estimation (Zhang et al, 2013). The study described here aimed to examine the consistency of airborne and surface-based measurements and to evaluate aerosol radiative characteristics and the distribution and transport of air pollutants both horizontally and vertically It is an integral part of, a foundation for, a series of studies on aerosol–cloud–climate interactions in a densely populated and rapidly developing region of China (Li et al, 2017a).
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