Changes in land use and land cover (LULC) influence meteorological fields and biogenic emissions, further affecting the atmospheric chemistry and air quality. Combining the satellite measurements and WRF‐Chem model simulations, we evaluate the impacts of the LULC change between 2001 and 2018 on the summertime ozone (O3) formation in North China Plain and surrounding areas (NCPs). Satellite measurements have revealed that from Taihang to Yanshan Mountain, the fraction of broadleaf and needle forest coverage has increased by 5%–20% and the urban area has increased by up to 25% in the NCP. Additionally, the vegetation density has increased significantly in the NCPs except for urban areas. The LULC change generally enhances biogenic volatile compounds emissions in the NCPs, particularly over Taihang and Yanshan mountain, but the O3 variation is divergent. The maximum daily 8‐ihr average (MDA8) O3 concentrations are reduced by 1%–7% over Taihang and Yanshan Mountain because the raised vegetation density increases O3 dry deposition velocity to accelerate the O3 loss. The raised vegetation density enhances the evapotranspiration to decrease the near‐surface temperature by 0.1°C–1.5°C, which also generates a divergence in the low‐level atmosphere in the NCPs, causing secondary northerly or easterly winds in the NCP. The O3 enhancement along the coastal areas of the NCP is attributed to the perturbation of wind fields and photolysis induced by the LULC change. The divergent variation of the MDA8 O3 concentrations in the NCP is generally caused by the variations of biogenic emissions and photolysis.

Transboundary transport plays an important role in air pollution formation in China. The coastal area of south China (CA‐SCHN) frequently experiences air pollution in spring and autumn, but the contribution of transboundary transport to the air quality is still not clear. Meteorological field analyses reveal that large‐scale synoptic patterns over east China in spring and autumn provide favorable situations facilitating southward transport of air pollutants originated from the North China Plain (NCP) and Yangtze River Delta (YRD). A springtime case study using the WRF‐Chem model shows that trans‐boundary transport of air pollutants from the NCP and YRD contributes to 27% and 46% of ozone (O3) and fine particulate matter (PM2.5) concentrations in the CA‐SCHN, respectively. In the autumn case, the contribution is around 11% for O3 and 24% for PM2.5. In the spring, air pollutants in the NCP and YRD are transported over seas by large‐scale synoptic systems to the South China Sea and re‐circulated by the sea breeze to the CA‐SCHN during daytime. In the autumn, the transport is driven by northerly winds over the land induced by large‐scale synoptic systems, and is also modulated by the local mountain‐valley breeze circulation. The results provide support for design and implementation of air pollutants control strategies in the CA‐SCHN.

Deserts have been recognized as constantly releasing reactive nitrogen compounds to the atmosphere due to the subsoil‐storage leaching and surface‐deposit evaporation induced by solar radiative heating. However, this release and the consequent response of the nitrogen cycles in desert air have not been evaluated and are overlooked in most regional and global models. In our nitrate measurements, including nitric acid and particulate nitrate, in clean air, that is, in the absence of or with minor anthropogenic influences, in a Chinese desert, diurnal nitrate variations consisting of daytime increases and nighttime decreases were observed in the range of 1.3–3.7 μgm−3 in summer, 0.1–2.6 μgm−3 in spring, and 0.2–1.3 μgm−3 in autumn. These values are considerably higher than those observed in remote marine and forest areas. Simulations with a regional transport model demonstrate that the variation could be largely accounted for by the oxidation of soil‐emitted reactive nitrogen compounds by photochemical‐reactions products. These results indicate an active nitrogen cycle in clean desert air, which is the consequence of the coordination of solar radiation‐induced surface soil emission and subsequent photochemical reactions. Satellite data of NO2 further indicate possible similar cycles in most major desert areas worldwide. By including this nitrogen cycle in the vast desert areas and its subsequent effects, such as those on ozone chemistry, climate models may thus provide a better understanding of the global nitrogen budget in the historical and developing Earth ecosystems.