Abstract
The Beijing-Tianjin-Hebei (BTH) region, with its complex terrain, has serious issues with air pollution. The northern and western parts of the BTH region are surrounded by the Yan Mountains and Loess Plateau (LP), and the south-central part of that region is a large open plain. Such special geographic configuration is prone to result in a concentrated pollution belt along the north-to-south direction on the eastern margin of the plateau, in addition to the influence of pollutant-emission sources and population distribution. In this study, based on an original adaptive nudging constraint method, we quantitatively analyzed the differences in the influence of emission sources under different dynamic and thermal conditions in the BTH region, which is impacted by a special large-scale leeward slope terrain. The mechanism of air pollution vulnerability and the comprehensive effects of terrain–meteorological conditions on air pollution in the BTH region were also discussed. The results indicated that the atmospheric diffusion conditions on the eastern side of the plateau were poor, and a sub-synoptic-scale “vortex sequence”, which was composed of a series of linked vortices, was identified. The corresponding atmospheric pollution convergence line stretched from Beijing to Hebei to Northern Henan in the lower atmosphere. On the eastern edge of the plateau, a “warm cover” formed by a temperature anomaly and a downdraft impeded the vertical diffusion of pollutants. Therefore, pollutants tended to converge at the eastern edge of the plateau, and the pollution belts would move longitudinally north and south along the topography of the eastern slope when south-westerly and north-easterly winds alternated. The movement generated a “train” of pollutants that were transported on the eastern edge of the plateau, which then caused air pollution to persist there. Such terrain–meteorological conditions amplified the effects of emissions by an average of 50% to 150% in the region, leading the eastern side of the LP to become a “naturally vulnerable region” to haze pollution.
Highlights
The Beijing-Tianjin-Hebei (BTH) region has been suffering from the most severe haze in China [1,2,3].Air pollution is closely related to the population density, industrial development, and the traffic intensity.Particulate matter, such as PM2.5, is the major pollutant of winter haze in the BTH region [4], and it has a negative impact on ambient air quality and human health [5,6,7]
BTH region in winter, using PM2.5 and NO2 ground observations and analyzed the spatial distribution of the atmospheric diffusion conditions using, atmospheric ventilation calculated based on wind fields reanalysis data
Surrounded by the “semi-enclosed” and the southward-opening terrain formed by the Loess Plateau (LP), a contamination conveyor belt is distributed along the topography of the EMLP in the BTH region
Summary
The Beijing-Tianjin-Hebei (BTH) region has been suffering from the most severe haze in China [1,2,3].Air pollution is closely related to the population density, industrial development, and the traffic intensity.Particulate matter, such as PM2.5 , is the major pollutant of winter haze in the BTH region [4], and it has a negative impact on ambient air quality and human health [5,6,7]. The Beijing-Tianjin-Hebei (BTH) region has been suffering from the most severe haze in China [1,2,3]. Air pollution is closely related to the population density, industrial development, and the traffic intensity. Particulate matter, such as PM2.5 , is the major pollutant of winter haze in the BTH region [4], and it has a negative impact on ambient air quality and human health [5,6,7]. In 2013, the Chinese government established the “Action Plan for Air Pollution Prevention and Control”. Since the implementation of this measure, pollution control has been moderately successful [8]. The monitoring results of the ozone monitoring instrument (OMI) indicated that the amount of NOX emissions in many cities in
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