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Opis: Basic concepts of laser-based technique LIDAR (LIght Detection and Ranging) are discussed in this article as well as advantages and disadvantages. Presented are measurements of relative particulate concentrations above an unpaved road which were performed in a rural area near the Iowa City, Iowa, USA. The LIDAR system used in these measurements is a small, scanning LIDAR that uses elastic backscattering to obtain information on the amount of atmospheric aerosols. In the elastic LIDAR, light scattered back towards the LIDAR system from molecules and particles in the atmosphere is collected by a telescope and is detected with a photodiode. A Big Sky Laser model CFR-200 Nd:YAG laser operating at 1.064 microns is used to generate the LIDAR's outgoing signal. The laser is attached directly to the top of a 26 cm, f/10 Cassegrian telescope. A series of pulses are summed to make a single scan. A series of scans is used to build up a two- dimensional map of relative atmospheric aerosol concentrations. With a maximum range of about 6-8 km, a range resolution of 2.5 m, and a time resolution of 30 s, the LIDAR is capable of very detailed mapping of aerosols.
Ključne besede: LIDAR technique, particulate concentration, traffic emissions
Objavljeno v RUNG: 12.07.2023; Ogledov: 247; Prenosov: 1
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Ključne besede: meritve lastnosti, vulkanski pepel, Ramanski lidar, observatorij CTA
Objavljeno v RUNG: 16.11.2022; Ogledov: 519; Prenosov: 0
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Opis: Aerosol direct radiative forcing is strongly dependent on aerosol distributions and aerosol types. A detailed understanding of such information is still missing at the Alpine region, which currently undergoes amplified climate warming. Our goal was to study the vertical variability of aerosol types within and above the Vipava valley (45.87◦ N, 13.90◦ E, 125 m a.s.l.) to reveal the vertical impact of each particular aerosol type on this region, a representative complex terrain in the Alpine region which often suffers from air pollution in the wintertime. This investigation was performed using the entire dataset of a dual-wavelength polarization Raman lidar system, which covers 33 nights from September to December 2017. The lidar provides measurements from midnight to early morning (typically from 00:00 to 06:00 CET) to provide aerosol-type dependent properties, which include particle linear depolarization ratio, lidar ratio at 355 nm and the aerosol backscatter Ångström exponent between 355 nm and 1064 nm. These aerosol properties were compared with similar studies, and the aerosol types were identified by the measured aerosol optical properties. Primary anthropogenic aerosols within the valley are mainly emitted from two sources: individual domestic heating systems, which mostly use biomass fuel, and traffic emissions. Natural aerosols, such as mineral dust and sea salt, are mostly transported over large distances. A mixture of two or more aerosol types was generally found. The aerosol characterization and statistical properties of vertical aerosol distributions were performed up to 3 km.
Ključne besede: valley air pollution, aerosol vertical distributions, lidar remote sensing, aerosol identification
Objavljeno v RUNG: 21.07.2022; Ogledov: 865; Prenosov: 23
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Opis: This paper complements the existing studies of Bora flow properties in the Vipava valley with the study of Bora turbulence in a lower region of the troposphere. The turbulence characteristics of Bora flow were derived from high resolution Doppler wind lidar measurements during eight Bora wind episodes that occurred in November and December 2019. Based on the vertical profiles of wind velocity, from 80 to 180 m above the valley floor, the turbulence intensity related to all three spatial directions and the along-wind integral length scales related to three velocity components were evaluated and compared to the approximations given in international standards. The resulting turbulence characteristics of Bora flow in a deep mountain valley exhibited interesting behaviour, differing from the one expected and suggested by standards. The intensity of turbulence during Bora episodes was found to be quite strong, especially regarding the expected values for that particular category of terrain. The specific relationship between along-wind, lateral and vertical intensity was evaluated as well. The scales of turbulence in the along-wind direction were found to vary widely between different Bora episodes and were rather different from the approximations given by standards, with the most significant deviations observed for the along-wind length scale of the vertical velocity component. Finally, the periodicity of flow structures above the valley was assessed, yielding a wide range of possible periods between 1 and 10 min, thus confirming some of the previous observations from the studies of Bora in the Vipava valley.
Ključne besede: doppler wind lidar, Bora wind, turbulence intensity, complex terrain, turbulence integral length scale
Objavljeno v RUNG: 05.11.2021; Ogledov: 1483; Prenosov: 41
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Opis: Razumevanje najbolj oddaljenih in nenavadnih pojavov v vesolju je lahko tesno povezano z razumevanjem pojavov tu na Zemlji. Iskanje odgovorov na vprašanja, ki jih znanosti denimo zastavljajo eksotični kozmični žarki visokih energij, je povezano s podrobnim razumevanjem Zemljine atmosfere, saj ima atmosfera vlogo ogromnega detektorja. Nova spoznanja ne odpirajo zgolj novih poglavij v našem razumevanju vesolja, ampak tudi vrsto novih možnosti pri razumevanju dejavnikov, ki vplivajo na naše vreme in podnebje. Tem vidikom se bomo posvetili v današnjih Podobah znanja. Naš gost je prof. dr. Samo Stanič, vodja Centra za astrofiziko in kozmologijo Univerze v Novi Gorici. Za vrhunske dosežke pri raziskavah kozmičnih delcev ekstremnih energij je skupaj s kolegoma Andrejem Filipčičem in Markom Zavrtanikom prejel Zoisovo nagrado.
Ključne besede: intervju, Zoisova nagrada, observatorij Pierre Auger, kozmični delci ekstremnih energij, atmosfera, lidar
Objavljeno v RUNG: 12.02.2021; Ogledov: 1915; Prenosov: 92
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