Bibliografie tematiche / Atmospheric microlidar

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Letteratura scientifica selezionata sul tema "Atmospheric microlidar"

Autore: Grafiati

Pubblicato: 3 agosto 2024

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Articoli di riviste sul tema "Atmospheric microlidar"

Arumov, G. P., e A. V. Bukharin. "Miniaturization of elastic scattering lidars: determination of the microstructure of the surface layer of the atmosphere". Izmeritel`naya Tekhnika, n. 4 (26 giugno 2024): 32–38. http://dx.doi.org/10.32446/0368-1025it.2024-4-32-38.

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Abstract (sommario):

Miniature elastic scattering lidars with similar schemes for determining the microstructure of the surface layer of the atmosphere are considered. In the considered microlidar model, it is assumed that in the limiting case there may be no particles in a small probed volume. In this case, the minimum value of the return signal corresponds to molecular scattering. The excess of the signal above this level is associated with the presence of a particle. The molecular component of the backscatter signal is constant and can be compared to a tabulated value of the backscatter coefficient using an optical atmospheric model. This makes it possible to compare the average value of the total backscattering signal from molecules and particles with the overall backscattering coefficient. A scheme similar to a microlidar, but on an enlarged scale – a minilidar – is considered. For both such schemes, the average values of atmospheric backscatter signals are the same. For a minilidar, the return signal is formed by scattering from a layer ranging in size from several meters to several tens of meters. In this case, the probed volume can be determined using perforated screens and reflective spheres. It is shown that the ratio of the probed volumes for the minilidar and microlidar is equal to the similarity coefficient to the fourth power. The considered lidars can be used to determine the concentration of equivalent particles.

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Krichbaumer, W. "Airborne Cloud Measurements with the DLR Microlidar during the CLEOPATRA Campaign". Journal of Atmospheric and Oceanic Technology 13, n. 1 (febbraio 1996): 54–57. http://dx.doi.org/10.1175/1520-0426(1996)013<0054:acmwtd>2.0.co;2.

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Mariage, Vincent, Jacques Pelon, Frédéric Blouzon, Stéphane Victori, Nicolas Geyskens, Nadir Amarouche, Christine Drezen et al. "IAOOS microlidar-on-buoy development and first atmospheric observations obtained during 2014 and 2015 arctic drifts". Optics Express 25, n. 4 (13 gennaio 2017): A73. http://dx.doi.org/10.1364/oe.25.000a73.

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Fierli, F., G. Di Donfrancesco, F. Cairo, V. Marécal, M. Zampieri, E. Orlandi e G. Durry. "Variability of cirrus clouds in a convective outflow during the Hibiscus campaign". Atmospheric Chemistry and Physics 8, n. 16 (6 agosto 2008): 4547–58. http://dx.doi.org/10.5194/acp-8-4547-2008.

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Abstract (sommario):

Abstract. Light-weight microlidar and water vapour measurements were taken on-board a stratospheric balloon during the HIBISCUS 2004 campaign, held in Bauru, Brazil (49° W, 22° S). Cirrus clouds were observed throughout the flight between 12 and 15 km height with a high mesoscale variability in optical and microphysical properties. It was found that the cirrus clouds were composed of different layers characterized by marked differences in height, thickness and optical properties. Simultaneous water vapour observations show that the different layers are characterized by different values of the saturation with respect to ice. A mesoscale simulation and a trajectory analysis clearly revealed that the clouds had formed in the outflow of a large and persistent convective region and that the observed variability of the optical properties and of the cloud structure is likely linked to the different residence times of the convectively-processed air in the upper troposphere.

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Chen, Lee Chuin, Tsubasa Naito, Satoshi Ninomiya e Kenzo Hiraoka. "Hyphenation of high-temperature liquid chromatography with high-pressure electrospray ionization for subcritical water LC-ESI-MS". Analyst 143, n. 22 (2018): 5552–58. http://dx.doi.org/10.1039/c8an01113c.

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Budke, C., e T. Koop. "BINARY: an optical freezing array for assessing temperature and time dependence of heterogeneous ice nucleation". Atmospheric Measurement Techniques 8, n. 2 (10 febbraio 2015): 689–703. http://dx.doi.org/10.5194/amt-8-689-2015.

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Abstract. A new optical freezing array for the study of heterogeneous ice nucleation in microliter-sized droplets is introduced, tested and applied to the study of immersion freezing in aqueous Snomax® suspensions. In the Bielefeld Ice Nucleation ARraY (BINARY) ice nucleation can be studied simultaneously in 36 droplets at temperatures down to −40 °C (233 K) and at cooling rates between 0.1 and 10 K min−1. The droplets are separated from each other in individual compartments, thus preventing a Wegener–Bergeron–Findeisen type water vapor transfer between droplets as well as avoiding the seeding of neighboring droplets by formation and surface growth of frost halos. Analysis of freezing and melting occurs via an automated real-time image analysis of the optical brightness of each individual droplet. As an application ice nucleation in water droplets containing Snomax® at concentrations from 1 ng mL−1 to 1 mg mL−1 was investigated. Using different cooling rates, a small time dependence of ice nucleation induced by two different classes of ice nucleators (INs) contained in Snomax® was detected and the corresponding heterogeneous ice nucleation rate coefficient was quantified. The observed time dependence is smaller than those of other types of INs reported in the literature, suggesting that the BINARY setup is suitable for quantifying time dependence for most other INs of atmospheric interest, making it a useful tool for future investigations.

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Ma, Chang-Jin, Cheol-Soo Lim e Takuro Sakai. "Preliminary Study on the Elemental Quantification of in Ambient Liquid Samples of Microliter Volume Using the In-air Micro-PIXE Technique". Asian Journal of Atmospheric Environment 11, n. 1 (31 marzo 2017): 54–60. http://dx.doi.org/10.5572/ajae.2017.11.1.054.

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Budke, C., e T. Koop. "BINARY: an optical freezing array for assessing temperature and time dependence of heterogeneous ice nucleation". Atmospheric Measurement Techniques Discussions 7, n. 9 (10 settembre 2014): 9137–72. http://dx.doi.org/10.5194/amtd-7-9137-2014.

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Abstract (sommario):

Abstract. A new optical freezing array for the study of heterogeneous ice nucleation in microliter-sized droplets is introduced, tested and applied to the study of immersion freezing in aqueous Snomax® suspensions. In the Bielefeld Ice Nucleation ARraY (BINARY) ice nucleation can be studied simultaneously in 36 droplets at temperatures down to −40 °C (233 K) and at cooling rates between 0.1 K min−1 and 10 K min−1. The droplets are separated from each other in individual compartments, thus preventing a Wegener–Bergeron–Findeisen type water vapor transfer between droplets as well as avoiding the seeding of neighboring droplets by formation and surface growth of frost halos. Analysis of freezing and melting occurs via an automated real time image analysis of the optical brightness of each individual droplet. As an application ice nucleation in water droplets containing Snomax® at concentrations from 1 ng mL−1 to 1 mg mL−1 was investigated. Using different cooling rates a minute time dependence of ice nucleation induced by Class A and Class C ice nucleators contained in Snomax® was detected. For the Class A IN a very strong increase of the heterogeneous ice nucleation rate coefficient with decreasing temperature of λ ≡ −dln(jhet)/dT = 8.7 K−1 was observed emphasizing the capability of the BINARY device. This value is larger than those of other types of IN reported in the literature, suggesting that the BINARY setup is suitable for quantifying time dependence for most other IN of atmospheric interest, making it a useful tool for future investigations.

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Kunert, Anna T., Mark Lamneck, Frank Helleis, Ulrich Pöschl, Mira L. Pöhlker e Janine Fröhlich-Nowoisky. "Twin-plate Ice Nucleation Assay (TINA) with infrared detection for high-throughput droplet freezing experiments with biological ice nuclei in laboratory and field samples". Atmospheric Measurement Techniques 11, n. 11 (23 novembre 2018): 6327–37. http://dx.doi.org/10.5194/amt-11-6327-2018.

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Abstract. For efficient analysis and characterization of biological ice nuclei under immersion freezing conditions, we developed the Twin-plate Ice Nucleation Assay (TINA) for high-throughput droplet freezing experiments, in which the temperature profile and freezing of each droplet is tracked by an infrared detector. In the fully automated setup, a couple of independently cooled aluminum blocks carrying two 96-well plates and two 384-well plates, respectively, are available to study ice nucleation and freezing events simultaneously in hundreds of microliter-range droplets (0.1–40 µL). A cooling system with two refrigerant circulation loops is used for high-precision temperature control (uncertainty <0.2 K), enabling measurements over a wide range of temperatures (∼ 272–233 K) at variable cooling rates (up to 10 K min−1). The TINA instrument was tested and characterized in experiments with bacterial and fungal ice nuclei (IN) from Pseudomonas syringae (Snomax®) and Mortierella alpina, exhibiting freezing curves in good agreement with literature data. Moreover, TINA was applied to investigate the influence of chemical processing on the activity of biological IN, in particular the effects of oxidation and nitration reactions. Upon exposure of Snomax® to O3 and NO2, the cumulative number of IN active at 270–266 K decreased by more than 1 order of magnitude. Furthermore, TINA was used to study aqueous extracts of atmospheric aerosols, simultaneously investigating a multitude of samples that were pre-treated in different ways to distinguish different kinds of IN. For example, heat treatment and filtration indicated that most biological IN were larger than 5 µm. The results confirm that TINA is suitable for high-throughput experiments and efficient analysis of biological IN in laboratory and field samples.

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Hawkins, Lelia Nahid, Hannah G. Welsh e Matthew V. Alexander. "Evidence for pyrazine-based chromophores in cloud water mimics containing methylglyoxal and ammonium sulfate". Atmospheric Chemistry and Physics 18, n. 16 (28 agosto 2018): 12413–31. http://dx.doi.org/10.5194/acp-18-12413-2018.

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Abstract. Simulating aqueous brown carbon (aqBrC) formation from small molecule amines and aldehydes in cloud water mimics provides insight into potential humic-like substance (HULIS) contributors and their effect on local and global aerosol radiative forcing. Previous work has shown that these (Maillard type) reactions generate products that are chemically, physically, and optically similar to atmospheric HULIS in many significant ways, including in their complexity. Despite numerous characterization studies, attribution of the intense brown color of many aqBrC systems to specific compounds remains incomplete. In this work, we present evidence of novel pyrazine-based chromophores (PBCs) in the product mixture of aqueous solutions containing methylglyoxal and ammonium sulfate. PBCs observed here include 2,5-dimethyl pyrazine (DMP) and products of methylglyoxal addition to the pyrazine ring. This finding is significant as the literature of Maillard reactions in food chemistry tightly links the formation of pyrazine (and related compounds) to browning in foods. We investigated the roles of both cloud processing (by bulk evaporation) and pH in absorptivity and product distribution in microliter samples to understand the contribution of these PBCs to aqBrC properties. In agreement with previous work, we observed elevated absorptivity across the entire UV–visible spectrum following simulated cloud processing as well as higher absorptivity in more basic samples. Absorptivity of the pH 2 sample, following evaporation over a period of days, exceeded that of the unevaporated pH 9 sample. In addition, mixtures of ammonium sulfate and methylglyoxal at pH 5 that were dried in under 1 h and analyzed 24 h later were as absorptive as pH 9 samples allowed to react for 7 days, indicating that evaporation occurring during cloud processing may provide a reaction pathway favorable for carbonyl–ammonia chemistry even under acidic conditions of aerosol and cloud water. The fraction of pyrazine compounds in the product mixture increased by up to a factor of 4 in response to drying with a maximum observed contribution of 16 % at pH 5. Therefore, cloud processing under acidic conditions may produce PBCs at the expense of imine- and imidazole-derived compounds. This finding has implications for further BrC reactivity and degradation pathways.

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Più fonti

Atti di convegni sul tema "Atmospheric microlidar"

Merrill, Marriner H. "Large-Scale Electrospray Ionization Methods for Nanocoating Application". In ASME 2010 International Mechanical Engineering Congress and Exposition. ASMEDC, 2010. http://dx.doi.org/10.1115/imece2010-38799.

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Abstract (sommario):

A scalable nano-coating process is needed that can be applied at atmospheric temperatures and pressures with low waste. This would enable the efficient production of advanced thin-film materials from solar cells to super-hydrophobic surfaces. Unfortunately, current methods for producing nanoparticle or nano-structured macromolecular coatings often require substrate immersion, specific atmospheres, and/or long growth times. One potential technique to overcome these challenges would be to use electrospray ionization (ESI) to first disperse large numbers of nanoparticles or polymers in air at standard conditions, and then deposit these on a substrate. ESI is a relatively mature technology, and although it has been developed largely for processing microliter volumes in mass spectrometry, it is believed that the fundamental science can be scaled up. This work presents a model for an ESI deposition method. It combines scaling laws for charged jets with spray and fission models to capture relevant charge, spray, fission, and evaporation phenomena. The developed model is shown to be very simple and efficient while still matching published experimental results. Using the model, current ESI techniques are compared such as NanoESI and Flow-Focusing ESI. A significant technological challenge to ESI deposition is discovered to be the trapping of the majority of the solute in a few primary droplets. Different solutions to this challenge are examined and used to define the direction for future work.

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