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Lidar Observations of Mountain Waves During Bora Episodes
Longlong Wang, Marija Bervida, Samo Stanič, Klemen Bergant, William Eichinger, Benedikt Strajnar, 2020, published scientific conference contribution

Abstract: Airflows over mountain barriers in the Alpine region may give rise to strong, gusty downslope winds, called Bora. Oscillations, caused by the flow over an orographic barrier, lead to formation of mountain waves. These waves can only rarely be observed visually and can, in general, not be reliably reproduced by numerical models. Using aerosols as tracers for airmass motion, mountain waves were experimentally observed during Bora outbreak in the Vipava valley, Slovenia, on 24-25 January 2019 by two lidar systems: a vertical scanning lidar positioned just below the peak of the lee side of the mountain range and a fixed direction lidar at valley floor, which were set up to retrieve two-dimensional structure of the airflow over the orographic barrier into the valley. Based on the lidar data, we determined the thickness of airmass layer exhibiting downslope motion, observed hydraulic jump phenomena that gave rise to mountain waves and characterized their properties.
Found in: ključnih besedah
Keywords: Bora, mountain waves, lidar observations
Published: 08.07.2020; Views: 1700; Downloads: 0
.pdf Fulltext (3,66 MB)

2020, radio or television broadcast

Abstract: 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.
Found in: ključnih besedah
Keywords: intervju, Zoisova nagrada, observatorij Pierre Auger, kozmični delci ekstremnih energij, atmosfera, lidar
Published: 12.02.2021; Views: 1361; Downloads: 77
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Kanarski otoki v plamenih
Uroš Slak, Samo Stanič, Natalija Švab, radio or television event

Abstract: Intervju o izbruhu ognjenika Cumbre Vieja na La Palmi, Kanarski otoki, Španjia, ter o raziskavah v okviru projekta Polje Čerenkovih teleskopov (CTA), ki potekajo na observatoriju Roque de los Muchachos.
Found in: ključnih besedah
Keywords: ognjenik, izbruh, astrofizika, gama žarki visokih energij, atmosfera, lidar
Published: 04.10.2021; Views: 927; Downloads: 0
.pdf Fulltext (189,76 KB)

Bora flow characteristics in a complex valley environment
Xiaoquan Song, Klemen Bergant, Longlong Wang, Griša Močnik, Samo Stanič, Marija Bervida, 2021, original scientific article

Abstract: 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.
Found in: ključnih besedah
Summary of found: ...were derived from high resolution Doppler wind lidar measurements during eight Bora wind episodes that...
Keywords: doppler wind lidar, Bora wind, turbulence intensity, complex terrain, turbulence integral length scale
Published: 05.11.2021; Views: 838; Downloads: 23
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Bioaerosol partitioning between the interstitial and condensed phase in mixed-phase clouds
Griša Močnik, Mojca Benčina, Samo Stanič, Miha Živec, Tina Šantl Temkiv, 2021, unpublished conference contribution

Found in: ključnih besedah
Keywords: bioaerosol, aerosol, mixed-phase clouds, LIDAR
Published: 22.11.2021; Views: 729; Downloads: 25
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Investigation of Aerosol Types and Vertical Distributions Using Polarization Raman Lidar over Vipava Valley
Longlong Wang, Marija Bervida Mačak, Samo Stanič, Klemen Bergant, Asta Gregorič, Luka Drinovec, Zhenping Yin, Yang Yi, Detlef Müller, Xuan Wang, 2022, original scientific article

Abstract: 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.
Found in: ključnih besedah
Keywords: valley air pollution, aerosol vertical distributions, lidar remote sensing, aerosol identification
Published: 21.07.2022; Views: 264; Downloads: 7
.pdf Fulltext (5,57 MB)

Investigation of the effective transmittance of Mach-Zehnder interferometer in the multi-longitudinal-mode high-spectral-resolution lidar
Fei Gao, Fengjia Gao, Xiao Yang, Gaipan Li, Li Wang, Meng Wang, Dengxin Hua, Griša Močnik, Samo Stanič, 2022, original scientific article

Abstract: Effective transmittance is an important parameter of Mach-Zehnder interferometer in the retrieval of aerosol optical properties using the multi-longitudinal-mode high-spectral-resolution lidar, which is a function of the complex degree of coherence. In this paper, we retrieve the parameter of the complex degree of coherence for the multi-longitudinal-mode laser from the theoretical analysis, optical simulation and experimental measurements, which are 0.726, 0.678 and 0.453 using the Mach-Zehnder interferometer with the optimal optical path difference of two times of laser optical cavity length (∼1000 mm) and under the light illumination of the high power Nd:YAG laser with the mode number of 101 and mode interval of 300 MHz under the condition of laser linewidth of 1 cm−1 (30 GHz). The preliminary measurement results of aerosol optical properties using the constructing multi-longitudinal-mode high-spectral-resolution lidar show that the difference of the complex degree of coherence retrieved from the presented methods results in the relative error of 40% in the aerosol backscattering coefficient with thin cloud layer and 90% with the presence of dense aerosol layer.
Found in: ključnih besedah
Keywords: effective transmittance, Mach-Zehnder interferometer, Multi-logitudinal-mode laser, High-spectral-resolution lidar
Published: 20.09.2022; Views: 99; Downloads: 0
.pdf Fulltext (4,32 MB)

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