A point cloud filtering method is presented for atmospheric layer detection from lidar data. The method involves rising edge event recognition based on a wavelet transform function. Density-based clustering was then utilized to separate the real boundary from the original noisy point clouds based on continuous distribution characteristics of cloud and aerosol layer. Tests were carried out to verify the performance of our algorithm with synthetic lidar signals with noise. The layer base detection error within ± 5 bins was achieved for signals with SNRs higher than 3. Even for SNRs higher than 1, high consistency was still observed between retrieved results with our method and a visual analysis. These results indicate that our algorithm is suitable for unsupervised detection with large time-series datasets, such as CALIOP.
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http://dx.doi.org/10.1364/OE.536588 | DOI Listing |
ACS Earth Space Chem
December 2024
Université Paris-Est Créteil and Université Paris Cité, CNRS, LISA, Créteil F-94010, France.
Hydroxyacetone (HA) is an atmospheric oxidation product of isoprene and other organic precursors that can form brown carbon (BrC). Measured bulk aqueous-phase reaction rates of HA with ammonium sulfate, methylamine, and glycine suggest that these reactions cannot compete with aqueous-phase hydroxyl radical oxidation. In cloud chamber photooxidation experiments with either gaseous or particulate HA in the presence of the same N-containing species, BrC formation was minor, with similar mass absorption coefficients at 365 nm (<0.
View Article and Find Full Text PDFPhotochem Photobiol Sci
December 2024
Institute of Meteorology and Climate Research Atmospheric Trace Gases and Remote Sensing, Karlsruhe Institute of Technology, Karlsruhe, Germany.
This paper investigates the evolution of changes in surface ultraviolet (UV) radiation globally, emphasizing the significant impacts of key factors influencing its variability, i.e., total column ozone, aerosols, clouds, and surface reflectivity.
View Article and Find Full Text PDFSci Total Environ
December 2024
Institute of Desert Meteorology, China Meteorological Administration/National observation and Research Station of Desert Meteorology, Taklimakan Desert of Xinjiang/Taklimakan Desert Meteorology Field Experiment Station of China Meteorological Administration/Xinjiang Key Laboratory of Desert Meteorology and Sandstorm/Key Laboratory of Tree-ring Physical and Chemical Research, China Meteorological Administration, Urumqi 830002, China.
The Tibetan Plateau (TP) is significantly influencing the climate and environmental evolution regionally and globally. Adjacent to the northwestern TP, the Taklimakan Desert (TD) experiences the unique pattern of dust aerosol variations due to the deep basin terrain. However, systematic studies on how TP climate change affects TD dust aerosol variations are lacking.
View Article and Find Full Text PDFEnviron Sci Technol
December 2024
Department of Atmospheric Sciences, Texas A&M University, College Station, Texas 77843, United States.
Phys Chem Chem Phys
December 2024
Department of Chemistry, University of Helsinki, FI-00014 Helsinki, Finland.
Quantum chemical calculations were employed to construct Jablonski diagrams for a series of phenolic carbonyls, including vanillin, iso-vanillin, 4-hydroxybenzaldehyde, syringaldehyde, and coniferyl aldehyde. These molecules can enter the Earth's atmosphere from forest fire emissions and participate in photochemical reactions within the atmospheric condensed phase, including cloud and fog droplets and aqueous aerosol particles. This photochemistry alters the composition of light-absorbing organic content, or brown carbon, in droplets and particles through the formation and destruction of key chromophores.
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