Despite the large number of domestic inland river vessels in China, information on inland ship emissions is very limited, since legislation for shipping emission control is limited and there is no monitoring infrastructure. Taking the Yangtze River in the region of Nanjing as a research area, we compiled a ship emission inventory based on real-time information received from automatic identification system (AIS) signals combined with ship-related data provided by the China Classification Society (CCS) database. The total ship emissions we derived for the Jiangsu section of the Yangtze River from September 2018 to August 2019 for NO_x, SO₂, PM₁₀ and PM_2.5 were 83.5, 0.04, 0.006 and 0.005 kt yr⁻¹, respectively. This ship emission inventory we constructed was compared with the Multi-resolution Emission Inventory for China (MEIC), the Shipping Emission Inventory Model (SEIM) and the satellite-derived emissions using the Daily Emissions Constrained by Satellite Observations (DECSO) algorithm. The results show a consistent spatial distribution, with riverine cities having high NO_x pollution. With this comparison we analyzed the relative impact of ship emissions on densely populated regions along the river. Inland ship emissions of NO_x are shown to contribute significantly, accounting for at least 40 % of air pollution close to the river.

Lightning serves as the dominant source of nitrogen oxides (${\mathrm{NO}}_x=\mathrm{NO}+{\mathrm{NO}}_{\mathrm{2}}$ ) in the upper troposphere (UT), with a strong impact on ozone chemistry and the hydroxyl radical production. However, the production efficiency (PE) of lightning nitrogen oxides (LNO_x) is still quite uncertain (32–1100 mol NO per flash). Satellite measurements are a powerful tool to estimate LNO_x directly compared to conventional platforms. To apply satellite data in both clean and polluted regions, a new algorithm for calculating LNO_x has been developed that uses the Berkeley High-Resolution (BEHR) v3.0B NO₂ retrieval algorithm and the Weather Research and Forecasting model coupled with chemistry (WRF-Chem). LNO_x PE over the continental US is estimated using the NO₂ product of the Ozone Monitoring Instrument (OMI) data and the Earth Networks Total Lightning Network (ENTLN) data. Focusing on the summer season during 2014, we find that the lightning NO₂ (LNO₂) PE is 32±15 mol NO₂ per flash and 6±3 mol NO₂ per stroke while LNO_x PE is 90±50 mol NO_x per flash and 17±10 mol NO_x per stroke. Results reveal that our method reduces the sensitivity to the background NO₂ and includes much of the below-cloud LNO₂. As the LNO_x parameterization varies in studies, the sensitivity of our calculations to the setting of the amount of lightning NO (LNO) is evaluated. Careful consideration of the ratio of LNO₂ to NO₂ is also needed, given its large influence on the estimation of LNO₂ PE.

The spatiotemporal statistical characteristics of warm-season deep convective systems, particularly deep convective systems initiation (DCSI), over China and its vicinity are investigated using Himawari-8 geostationary satellite measurements collected during April-September from 2016 to 2020. Based on a satellite brightness temperature multiple-threshold convection identification and tracking method, a total of 47593 deep convective systems with lifetimes of at least 3 h were identified in the region. There are three outstanding local maxima in the region, located in the southwestern, central and eastern Tibetan Plateau and Yunnan-Guizhou Plateau, followed by a region of high convective activities in South China. Most convective systems are developed over the Tibetan Plateau, predominantly eastward-moving, while those developed in Yunnan-Guizhou Plateau and South China mostly move westward and southwestward. The DSCI occurrences become extremely active after the onset of the summer monsoon and tend to reach a maximum in July and August, with a diurnal peak at 11–13 LST in response to the enhanced solar heating and monsoon flows. Several DCSI hotspots are identified in the regions of inland mountains, tropical islands and coastal mountains during daytime, but in basins, plains and coastal areas during nighttime. DCSI over land and oceans exhibits significantly different sub-seasonal and diurnal variations. Oceanic DCSI has an ambiguous diurnal variation, although its sub-seasonal variation is similar to that over land. It is demonstrated that the high spatiotemporal resolution satellite dataset provides rich information for understanding the convective systems over China and vicinity, particularly the complex terrain and oceans where radar observations are sparse or none, which will help to improve the convective systems and initiation nowcasting.

Solid waste is the third largest source of anthropogenic methane, and mitigating emissions is crucial for addressing climate change. We combine three high-resolution (30-60 m) hyperspectral satellite imagers (EMIT, EnMAP, and PRISMA) to quantify emissions from 38 strongly emitting disposal sites across worldwide urban methane hotspots. The imagers give consistent emission estimates, with EMIT and EnMAP having better sensitivity than PRISMA. Total observed emissions add up to 230 ± 15 t h^-1, representing 5% of reported global solid waste emissions. Our estimates exceed the facility-level Climate TRACE inventory by a factor of 1.8, while we only detect emissions from 9 of the inventory's 20 highest-emitting sites, highlighting the importance of facility-level information. Furthermore, multimonth observations reveal emission patterns potentially linked to facility operations. We estimate that these instruments could detect 35-60% of global landfill emissions, critically expanding on satellite instruments designed for methane and supporting emission mitigation.

Thunderstorms can significantly influence the air composition via strong updraft and lightning nitrogen oxides (LNO_x). In this study, the ozonesondes and TROPOMI (TROPOspheric Monitoring Instrument) nitrogen dioxide (NO₂) observations for two cases are combined with a model to investigate the effects of typical strong convection on vertical redistribution of air pollutants in Nanjing, southeastern China. The ozonesonde observations show higher O₃ and water vapor mixing ratios in the upper troposphere (UT) after convection, indicating the strong updraft transporting lower-level air masses into the UT and the possible downward O₃-rich air near the top of UT over the convective period. During the whole convection life cycle, the UT O₃ production is driven by the chemistry (5–10 times the magnitude of dynamic contribution) and reduced by the LNO_x (−40 %). Sensitivity tests demonstrate that neglecting LNO_x in standard TROPOMI NO₂ products causes overestimated air mass factors over fresh lightning regions and the opposite for outflow and aged lightning areas. Therefore, a new high-resolution retrieval algorithm is applied to estimate the LNO_x production efficiency. Our work shows the demand for high-resolution modeling and satellite observations on LNO_x emissions of both active and dissipated convection, especially small-scale storms.