Yonghua Wu

This study presents a multi-instrument remote sensing approach to characterize the optical properties and vertical distribution of aerosols within the planetary boundary layer (PBL) over New York City during the COVID-19 pandemic and post-pandemic periods. The analysis focuses on changes in aerosol loading associated with variations in anthropogenic activity and examines the relationship between column-integrated aerosol optical properties, vertically resolved aerosol distributions, and near-surface fine particulate matter (PM2.5). Continuous ceilometer observations are used to characterize profiles of attenuated backscatter and to investigate aerosol vertical structure and variability within the PBL. These measurements are complemented by sun-photometer observations of column-integrated aerosol optical properties, radiosonde profiles of atmospheric thermodynamic structure, and ground-based PM2.5 measurements. The synergistic use of these datasets provides a more comprehensive characterization of aerosol optical and physical properties under varying meteorological and boundary-layer conditions than can be obtained from individual instruments alone. In addition, air-mass back trajectories calculated using the Hybrid Single-Particle Lagrangian Integrated Trajectory (HYSPLIT) model are employed to investigate the potential influence of local, regional, and long-range aerosol transport on observed aerosol variability over New York City. Comparisons between the pandemic and post-pandemic periods reveal substantial differences in aerosol loading and pollution levels, highlighting the combined influence of changes in anthropogenic emissions, PBL dynamics, meteorological conditions, and transported aerosol on the urban aerosol environment. The results demonstrate the value of integrating vertically resolved active remote sensing with columnar and surface observations and atmospheric transport modeling for assessing temporal changes in urban aerosol distributions and their controlling processes.

We present coordinated observations from ozone Differential Absorption lidar (DIAL), aerosol lidar, and Doppler wind lidar at the City College of New York (CCNY) in northern Manhattan during the summer 2023 AGES+ campaigns across the New York City (NYC) region and Long Island Sound (LIS) areas. The results highlight significant ozone formation within the planetary boundary layer (PBL) and the concurrent transport of ozone/aerosol plumes aloft and mixing into the PBL during 26–28 July 2023. Especially, 26 July experienced the highest ozone concentration within the PBL during the three-day ozone episode despite having a lower temperature than the following two days. In addition, the onset of the afternoon sea breeze contributed to increased ozone levels in the PBL. A mobile ozone DIAL was also deployed at Columbia University’s Lamont–Doherty Earth Observatory (LDEO) in Palisades, NY, 29 km north of NYC, from 11 August to 8 September 2023. A notable high-ozone episode was observed by both ozone DIALs at the CCNY and the LDEO site during an unusual heatwave event in early September. On 7 September, the peak ozone concentration at the LDEO reached 120 ppb, exceeding the ozone levels observed in NYC. This enhancement was associated with urban plume transport, as indicated by wind lidar measurements, the HRRR (High-Resolution Rapid Refresh) model, and the Copernicus Sentinel-5 TROPOMI (TROPOspheric Monitoring Instrument) tropospheric column NO₂ product. The results also show that, during both heatwave events, those days with slow southeast to southwest winds experienced significantly higher ozone pollution.

Water resources play an extremely important role in sustainable development. The hydrological processes from evapotranspiration to precipitation reshape the distribution of surface water resources, and a thorough understanding of these processes can contribute to water resources management. China has experienced vegetation greening in recent years. How China’s evapotranspiration, particularly vegetation-related evapotranspiration (transpiration and interception loss), regulates its own water resources effectiveness and the precipitation in surrounding countries remains unclear. Using a high-quality global atmospheric moisture connectivity, evapotranspiration, and precipitation dataset, we find that the regulatory effect of evapotranspiration on precipitation is most pronounced in summer. Annually in China, 57% of the moisture generated by evapotranspiration stays within China, accounting for 39.54% of precipitation sources. The remaining moisture is transported abroad, providing an important source of precipitation for the neighboring countries, especially North Korea and Mongolia. Although grasslands and bare areas contribute much less moisture than croplands and forests, they serve as critical moisture sources for the arid interior of China and Mongolia. Vegetation in China has a negative net hydrological effect domestically, which tends to increase across most parts of the country from 2000 to 2020. This research highlights the critical role of vegetation in the transboundary distribution of water resources through moisture transport and provides new insights for sustainable development of water resources.