ABSTRACT
The analysis of the daily spatial patterns of near-surface Nitrogen dioxide (NO2) concentrations can assist decision makers mitigate this common air pollutant in urban areas. However, comparative analysis of NO2 estimates in different urban agglomerations of China is limited. In this study, a new linear mixed effect model (LME) with multi-source spatiotemporal data is proposed to estimate daily NO2 concentrations at high accuracy based on the land-use regression (LUR) model and Ozone Monitoring Instrument (OMI) and TROPOspheric Monitoring Instrument (TROPOMI) products. In addition, three models for NO2 concentration estimation were evaluated and compared in four Chinese urban agglomerations from 2018 to 2020, including the COVID-19 closed management period. Each model included a unique combination of methods and satellite NO2 products: ModelⅠ: LUR model with OMI products;Model Ⅱ: LUR model with TropOMI products;Model Ⅱ: LME model with TropOMI products. The results show that the LME model outperformed the LUR model in all four urban agglomerations as the average RMSE decreased by 16.09% due to the consideration of atmospheric dispersion random effects, and using TropOMI instead of OMI products can improve the accuracy. Based on our NO2 estimations, pollution hotspots were identified, and pollution anomalies during the COVID-19 period were explored for two periods;the lockdown and revenge pollution periods. The largest NO2 pollution difference between the hotspot and non-hotspot areas occurred in the second period, especially in the heavy industrial urban agglomerations. © 2022 Elsevier Ltd
ABSTRACT
Understanding near-surface atmospheric behavior in the tropics is imperative given the role of tropical energy fluxes in Earth’s climate cycles, but this area is complicated by a land–atmosphere interaction that includes rugged to-pography, seasonal weather drivers, and frequent environmental disturbances. This study examines variation in nearsurface atmospheric behaviors in northeastern Puerto Rico using a synthesis of data from lowland and montane locations under different land covers (forest, urban, and rural) during 2008–21, when a severe drought, large hurricanes (Irma and Maria), and the COVID-19 mobility-reducing lockdown occurred. Ceilometer, weather, air quality, radiosonde, and satellite data were analyzed for annual patterns and monthly time series of data and data correlations. The results showed a system that is strongly dominated by easterly trade winds transmitting regional oceanic patterns over terrain. Environmental disturbances affected land–atmosphere interaction for short time periods after events. Events that reduce the land signature (reducing greenness: e.g., drought and hurricanes, or reducing land pollution: e.g., COVID-19 lockdown) were evidenced to strengthen the transmission of the oceanic pattern. The most variation in near-surface atmospheric behavior was seen in the mountainous areas that were influenced by both factors: trade winds, and terrain-induced orographic lifting. As an exception to the rest of the near-surface atmospheric behavior, pollutants other than ozone did not correlate positively or negatively with stronger trade winds at all sites across the region. Instead, these pollutants were hypothesized to be more anthropogenically influenced. Once COVID-19 lockdown had persisted for 3 months, urban pollution decreased and cloud base may have increased. © 2022, American Meteorological Society. All rights reserved.
ABSTRACT
Surface plasmon has a history of more than one hundred years since its birth and has been a brand new discipline-plasmonics. Localized surface plasmon in metal nanostructures can gain very strong near-surface electric field enhancement and has been applied to many types researches successfully. However, there is relatively less study of the interaction between localized surface plasmon and magnetic field in incident light. This paper calculates the near-surface electromagnetic field enhancement of metal nanosphere-nanodisc gap based on the previous achievement. This paper shows that under the excitation of the single tightly radially polarized optical beam, the metal nanodisc can produce localized surface plasmon breathing mode and electric dipole moment mode, which give rise to the longitudinal electric field enhancement at the nanodisc center. And then, because of the resonance interaction of the metal nanodisc and localized surface plasmon electric dipolar moment of the metal nanosphere, a gap mode of localized surface plasmon resonance with efficient longitudinal electric field enhancement can be produced. Through carrying out the numerical simulation, this paper demonstrates that the near-surface longitudinal electric field of metal nanostructure gap mode can obtain 250 times electrical field enhancement relative to the valid transverse electrical field that is used to excite the breathing mode, and the enhancement factor of near-surface magnetic field could be 170. In order to present more clearly the character of the spectrum and the near-surface electromagnetic field distribution of this new metal nanostructure, the near-surface electromagnetic field distribution and the resonant wavelengths of this new metal nanostructure are also studied. The calculation results show that the proposed metal nanosphere-nanodisc nanostructure owns an obvious advantage on the local near-surface electromagnetic field enhancement and a relatively large frequency spectrum. Due to the electromagnetic field enhancement advantage of the metal nanostructure proposed by this paper, the future is not without hope that the results here could be applied to more and more researches, especially biomedicine, and provide a bit of reference in order to fight for novel coronavirus. © 2022, Peking University Press. All right reserved.