Published by Copernicus Publications on behalf of the European Geosciences Union. 8340 X. Lu et al.: Exploring 2016-2017 surface ozone pollution over ChinaBVOC ozone enhancements) and ozone chemical production, increase the thermal decomposition of peroxyacetyl nitrate (PAN), and further decrease ozone dry deposition velocity. More stringent emission control measures are thus required to offset the adverse effects of unfavorable meteorology, such as high temperature, on surface ozone air quality.

Purpose: Vigorous physical activity is often considered a risk factor for knee and hip osteoarthritis (OA), but its effect on spinal OA is poorly

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Intensive agricultural activities in the North China Plain (NCP) lead to substantial emissions of nitrogen oxides (NOx) from soil, while the role of this source on local severe ozone pollution is unknown. Here we use a mechanistic parameterization of soil NOx emissions combined with two atmospheric chemistry models to investigate the issue. We find that the presence of soil NOx emissions in the NCP significantly reduces the sensitivity of ozone to anthropogenic emissions. The maximum ozone air quality improvements in July 2017, as can be achieved by controlling all domestic anthropogenic emissions of air pollutants, decrease by 30% due to the presence of soil NOx. This effect causes an emission control penalty such that large additional emission reductions are required to achieve ozone regulation targets. As NOx emissions from fuel combustion are being controlled, the soil emission penalty would become increasingly prominent and shall be considered in emission control strategies.

Statistical analyses were conducted to investigate the nighttime medium‐scale traveling ionospheric disturbances (MSTIDs) for the first time by using airglow images and Global Positioning System (GPS) data over central China during 2013–2015. Our results show that the phase fronts of perturbations are aligned from northwest to southeast direction and propagate toward the southwest direction. The characteristics of the nighttime MSTIDs observed by OI 630.0 nm images are consistent with those of the nighttime MSTIDs obtained from the GPS data. The phase velocity, period, wavelength, and amplitude of nighttime MSTIDs are 50–150 m/s, 0.5–1.5 h, 150–400 km, and 2%–15%, respectively, as measured from 630.0 nm images and GPS data. In addition, we utilized the simultaneous observations from OI 630.0 nm and OI 557.7 nm images to explore the relationship between nighttime MSTIDs and gravity waves (<100 km) in the mesopause. It is found that the nighttime MSTIDs frequently occurred in the summer solstice, which was not consistent with the occurrence of gravity wave observed in the mesopause. Our results indicate that the nighttime MSTIDs may be generated by the coupling of electrodynamic processes rather than be trigged by gravity waves from the lower atmosphere.

Abstract. China is facing a severe ozone problem, but the origin of its ozone remains unclear. Here we use a GEOS-Chem based global–regional two-way coupled model system to quantify the individual contributions of eight emission source regions worldwide to springtime ozone in 2008 over China. The model reproduces the observed ozone from 31 ground sites and various aircraft and ozonesonde measurements in China and nearby countries, with a mean bias of 10 %–15 % both near the surface and in the troposphere. We then combine zero-out simulations, tagged ozone simulations, and a linear weighting approach to account for the effect of nonlinear chemistry on ozone source attribution. We find considerable contributions of total foreign anthropogenic emissions to surface ozone over China (2–11 ppb). For ozone of anthropogenic origin averaged over China, foreign regions together contribute 40 %–60 % below the height of 2 km and 85 % in the upper troposphere. For total ozone contributed by foreign anthropogenic emissions over China at various heights, the portion of transboundary ozone produced within foreign emission source regions is less than 50 %, with the rest produced by precursors transported out of those source regions. Japan and Korea contribute 0.6–2.1 ppb of surface ozone over the east coastal regions. Southeast Asia contributes 1–5 ppb over much of southern China and South Asia contributes up to 5–10 ppb of surface ozone over the border of southwestern China; and their contributions increase with height due to strong upwelling over the source regions. The European contribution reaches 2.1–3.0 ppb for surface ozone over the northern border of China and 1.5 ppb in the lower troposphere averaged over China. North America contributes 0.9–2.7 ppb of surface ozone over most of China (1.5–2.1 ppb over the North China Plain), with a China average at 1.5–2.5 ppb at different heights below 8 km, due to its large anthropogenic emissions and the transport-favorable midlatitude westerly wind. In addition to domestic emission control, global emission reduction is critical for China's ozone mitigation.

Urban vitality, as a metric, measures the attractiveness and competitiveness of a city and is a driver of development. As the physical and social space of human activities, the urban landscape has close connections with urban vitality according to classical theories. However, limited quantitative criteria for the urban landscape and gaps between macro urban planning and micro design create difficulties when constructing a vibrant city. In this study, we quantitatively examined the relationship between the urban landscape and urban vitality at the street block level using geospatial open data to discover where, how, and to what extent we could improve urban vitality, taking 15 Chinese metropolises as a case study. Results indicate that, among the three aspects of the urban landscape considered, the city plan pattern has the highest effect on stimulating vitality, followed by the land use and the patterns of building form. Specifically, the three-dimensional form of buildings has a greater effect than a two-dimensional form. In addition, convenient transportation, a compact block form, diverse buildings, mixed land use, and high buildings are the main characteristics of vibrant blocks. The results also show that the effects of the urban landscape have spatial variations and obvious diurnal discrepancies. Furthermore, over 20 and 33% of the blocks in these cities are identified as low-vitality blocks during the day and night, respectively, and are then categorized into six different types. The identification of the common characteristics of these low-vitality blocks can be taken as references for designing a vibrant urbanity.

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