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Vertical distributions of air pollutants are crucial for understanding the key processes of atmospheric transport and for evaluating chemical transport models. In this paper, we present measurements of non-methane hydrocarbons (NMHCs) and halocarbons obtained from an intensive aircraft study over northeast (NE) China in summer 2007. Most compounds exhibited a typical negative profile of decreasing mixing ratios with increasing altitude, although the gradients differed with different species. Three regional plumes with enhanced VOC mixing ratios were discerned and characterized. An aged plume transported from the northern part of the densely populated North China Plain (NCP; i.e. Beijing-Tianjin area) showed relatively higher levels of HCFC-22, 1,2-dichloroethane (1,2-DCE) and toluene. In comparison, the plume originating from Korea had higher abundances of CFC-12, tetrachloroethene (C2Cl4) and methyl chloride (CH3Cl), while regional air masses from NE China contained more abundant light alkanes. By comparing these results with the earlier PEM-West B (1994) and TRACE-P (2001) aircraft measurements, continuing declining trends were derived for methyl chloroform (CH3CCl3), tetrachloromethane (CCl4) and C2Cl4 over the greater China-northwestern Pacific region, indicating the accomplishment of China in reducing these compounds under the Montreal protocol. However, the study also provided evidence for the continuing emissions of several halocarbons in China in 2007, such as CFCs (mainly from materials in stock) and HCFCs. © 2011 Elsevier Ltd.

Using high-precision microbarograph data and radar data to analyze the gravity fluctuation characteristics of four convective processes of different intensities that occurred in the Beijing–Tianjin–Hebei region in June 2018, the results show that convective cases are accompanied by gravity fluctuations of different time scales and can be separated from the background field through the wavelet transform. The stronger the convective process, the larger the fluctuation amplitude. As the convection gradually approaches the station, the fluctuation frequency broadens, and smaller period fluctuations are excited. Through Fourier analysis, the longer period of fluctuation is concentrated at about 190 min, and the power spectrum of the short-period fluctuation is weak, with a peak frequency of about 2.04 × 10−4 Hz. The results obtained by wavelet transform are similar to them, but they reflect the characteristics of fluctuation evolution over time: (1) convection-related gravity wave periods are mainly concentrated in three bands: 15–40 min, 40–120 min, and 120–250 min; (2) there may be precursor activity before the occurrence of the convective flow, and the long-period fluctuation occurs about 1–4 h ahead of time; (3) there is a short-period fluctuation in the process of convective system development, and the period range is mainly concentrated at about 40–120 min; strong convective clouds may inspire shorter-period fluctuations. The geometrical relationship between the microbarograph stations shows that the short-period fluctuations of the four convective cases propagate at a speed of 14–37 m/s, and the azimuthal angle is consistent with the convective orientation, which indicates that there is a close relationship between gravity waves and convection. [ABSTRACT FROM AUTHOR]