Abstract. A Nationwide Nitrogen Deposition Monitoring Network (NNDMN) containing 43 monitoring sites was established in China to measure gaseous NH3, NO2, and HNO3 and particulate NH4+ and NO3− in air and/or precipitation from 2010 to 2014. Wet/bulk deposition fluxes of Nr species were collected by precipitation gauge method and measured by continuous-flow analyzer; dry deposition fluxes were estimated using airborne concentration measurements and inferential models. Our observations reveal large spatial variations of atmospheric Nr concentrations and dry and wet/bulk Nr deposition. On a national basis, the annual average concentrations (1.3–47.0 μg N m−3) and dry plus wet/bulk deposition fluxes (2.9–83.3 kg N ha−1 yr−1) of inorganic Nr species are ranked by land use as urban > rural > background sites and by regions as north China > southeast China > southwest China > northeast China > northwest China > Tibetan Plateau, reflecting the impact of anthropogenic Nr emission. Average dry and wet/bulk N deposition fluxes were 20.6 ± 11.2 (mean ± standard deviation) and 19.3 ± 9.2 kg N ha−1 yr−1 across China, with reduced N deposition dominating both dry and wet/bulk deposition. Our results suggest atmospheric dry N deposition is equally important to wet/bulk N deposition at the national scale. Therefore, both deposition forms should be included when considering the impacts of N deposition on environment and ecosystem health.

No abstract

This paper proposes an explicit reference governor-based control scheme for the velocity-free spacecraft attitude maneuver problem subject to the pointing constraint, the angular velocity constraint, and the input constraint. The proposed two-layer control scheme guarantees asymptotic stability of the attitude while satisfying the aforementioned constraints. The inner layer relies on output feedback control via an immersion and invariance technology-based angular velocity observer, enabling attitude stabilization without measuring angular velocity. By analyzing the geometry of the pointing constraint, the upper bound of the angular velocity, and the optimization solution of the control input, the safety boundary described by the invariant set is obtained in the reference layer. Additionally, we introduce the dynamic factor related to the angular velocity estimation error into the invariant set to prevent states from exceeding the constraint set due to unmeasurable angular velocity information. The shortest guidance path is then designed in the reference layer. Finally, we verify the effectiveness of the proposed constrained attitude control algorithm through numerical simulations.

Abstract. Atmospheric ice nucleation plays an important role in modifying the global hydrological cycle and atmospheric radiation balance. To date, few comprehensive field observations of ice nuclei have been carried out at high-altitude sites, which is close to the height of mixed-phase cloud formation. In this study, we measured the concentrations of ice-nucleating particles (INPs) in the immersion freezing mode at the summit of Changbai Mountain (2623 m above sea level), Northeast Asia, in summer 2021. The cumulative number concentration of INPs varied from 3.8 × 10−3 L−1 to 2.3 L−1 over the temperature range from −20.5 °C to −5.5 °C. Proteinaceous-based biological materials accounted for the majority of INPs, with the proportion of biological INPs (bio-INPs) exceeding 75 % across the entire freezing temperature range, with this proportion even exceeding 90 % above −13.0 °C. At freezing temperatures ranging from −11 °C to −8 °C, bio-INPs were found to significantly correlate with wind speed and Ca2+, and weakly correlate with isoprene and its oxidation products (isoprene × O3), suggesting that biological aerosols may attach to soil dust surfaces and contribute to INPs. During the daytime, bio-INPs showed a positive correlation with the planetary boundary layer height, with the valley breezes from southwestern mountainous regions also influencing the concentration of INPs. Moreover, the long-distance transport of air mass from the Japan Sea and South Korea significantly contributed to the high concentrations of bio-INPs. Our study emphasizes the important role of biological sources of INPs in the high-altitude atmosphere of northeastern Asia, as well as the significant contribution of long-range transport to the INPs concentrations in this region.