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202. Near-Ground Profile of Bora Wind Speed at Razdrto, SloveniaMarija Bervida, Samo Stanič, Klemen Bergant, Benedikt Strajnar, 2019, izvirni znanstveni članek Opis: Southwest Slovenia is a region well-known for frequent episodes of strong and gusty Bora wind, which may damage structures, affect traffic, and poses threats to human safety in general. With the increased availability of computational power, the interest in high resolution modeling of Bora on local scales is growing. To model it adequately, the flow characteristics of Bora should be experimentally investigated and parameterized. This study presents the analysis of wind speed vertical profiles at Razdrto, Slovenia, a location strongly exposed to Bora during six Bora episodes of different duration, appearing between April 2010 and May 2011. The empirical power law and the logarithmic law for Bora wind, commonly used for the description of neutrally stratified atmosphere, were evaluated for 10-min averaged wind speed data measured at four different heights. Power law and logarithmic law wind speed profiles, which are commonly used in high resolution computational models, were found to approximate well the measured data. The obtained power law coefficient and logarithmic law parameters, which are for modeling purposes commonly taken to be constant for a specific site, were found to vary significantly between different Bora episodes, most notably due to different wind direction over complex terrain. To increase modeling precision, the effects of local topography on wind profile parameters needs to be experimentally assessed and implemented.
Ključne besede: Bora wind, logarithmic law, power law, roughness length, wind profile
Objavljeno v RUNG: 04.10.2019; Ogledov: 3461; Prenosov: 109
 Celotno besedilo (5,90 MB) |
203. Space weather research with the Pierre Auger ObservatoryMiha Živec, 2019, magistrsko delo Opis: Space weather refers to environmental conditions in the interplanetary space and Earth’s
magnetosphere, ionosphere and exosphere and can influence the performance and reliability
of electronics based technological systems. The major role in space weather
changes plays the solar wind, a stream of charged particles (mostly electrons and protons)
with energies of approximately 1 keV, that can cause geomagnetic storms and auroras.
During their entry into the atmosphere, high energy cosmic rays collide with atomic
nuclei of atmospheric gasses. When scattering occurs extensive air showers are created.
Those cascades of secondary particles create flashes of light due to the Cherenkov
effect as well as excite molecules of nitrogen gas in atmosphere, which then glow in
fluorescent light. In order to observe the light created by air showers, it has to be
collected with telescopes. The particles from the cascades that reach ground can be
detected with surface detectors. The Pierre Auger Observatory is the largest observatory
for cosmic ray measurements. It is located in Argentinian pampas covering an area of
3000 km2. It consists of 1660 surface detectors and 27 fluorescence telescopes. For
cosmic rays with energies above few 1017 eV, a precise reconstruction of energy and
direction of primary particle is achievable. Observatory also allows measurement of
flux of incoming particles down to primary energies in ca. 10 GeV - 10 TeV interval, with a median energy ca. 80-90 GeV. This measurement capability is called "scaler"
mode, since the corresponding data consist of scaler counted cascade particles with
deposited energy between 15 and 100 MeV, at the average rate of 2 kHz per individual
surface detector.
For the purpose of this master thesis I compared the data from scaler mode measurements
with measurements of neutron monitors, which are commonly used for space weather
observations. With the correlation received from the comparison, I showed that scaler
mode operation of Pierre Auger observatory can be used to monitor space weather events
such as solar cycle and the decreases in the observed galactic cosmic ray intensity due
to solar wind (Forbush decrease).
Ključne besede: Pierre Auger Observatory, cosmic rays, space weather, Forbush decrease
Objavljeno v RUNG: 17.09.2019; Ogledov: 4988; Prenosov: 181
Celotno besedilo (5,21 MB) |
204. Raman LIDARs and atmospheric calibration along the line-of-sight of the Cherenkov Telescope ArraySamo Stanič, Longlong Wang, Marko Zavrtanik, 2019, objavljeni znanstveni prispevek na konferenci Opis: The Cherenkov Telescope Array (CTA) is the next generation ground-based observatory for
gamma-ray astronomy at very-high energies. Employing more than 100 (north and south sites)
Imaging Atmospheric Cherenkov Telescopes in the northern and southern hemispheres, it was
designed to reach unprecedented sensitivity and energy resolution. Understanding and correcting
for systematic biases on the absolute energy scale and instrument response functions will be a cru-
cial issue for the performance of CTA. The Montpellier group and the Spanish/Italian/Slovenian
collaboration are currently building two Raman LIDAR prototypes for the online atmospheric cal-
ibration along the line-of-sight of the CTA. Requirements for such a solution include the ability
to characterize aerosol extinction at two wavelengths to distances up to 30 km with an accuracy
better than 5%, within exposure time scales of about a minute, steering capabilities and close
interaction with the CTA array control and data acquisition system as well as other auxiliary in-
struments. Our Raman LIDARs have design features that make them different from those used
in atmospheric science and are characterized by large collecting mirrors (∼2.5 m 2 ), liquid light-
guides that collect the light at the focal plane and transport it to the readout system, reduced
acquisition time and highly precise Raman spectrometers. The Raman LIDARs will participate in
a cross-calibration and characterization campaign of the atmosphere at the CTA North site at La
Palma, together with other site characterization instruments. After a one-year test period there, an
in-depth evaluation of the solutions adopted by the two projects will lead to a final Raman LIDAR
design proposal for both CTA sites.
Ključne besede: Raman lidar atmospheric calibration Cherenkov Telescope Array
Objavljeno v RUNG: 29.08.2019; Ogledov: 3382; Prenosov: 102
Celotno besedilo (1,29 MB) |
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207. Evaluation and Improvement of Lidar Performance Based on Temporal and Spatial Variance CalculationFei Gao, Xinxin Xu, Qingsong Zhu, Li Wang, Tingyao He, Longlong Wang, Samo Stanič, Dengxin Hua, 2019, izvirni znanstveni članek Ključne besede: spatial variance, temporal variance, analog data, photon-counting data, dead time, threshold voltage, linear working range, data gluing
Objavljeno v RUNG: 06.05.2019; Ogledov: 3360; Prenosov: 0
Gradivo ima več datotek! Več... |
208. Multi-Messenger Physics With the Pierre Auger ObservatoryKarl-Heinz Kampert, Andrej Filipčič, Gašper Kukec Mezek, Samo Stanič, Marta Trini, Serguei Vorobiov, Lili Yang, Danilo Zavrtanik, Marko Zavrtanik, Lukas Zehrer, 2019, izvirni znanstveni članek Ključne besede: Pierre Auger Observatory, ultra-high energy cosmic rays, photons, neutrinos, protons, multi-messenger physics and astrophysics
Objavljeno v RUNG: 06.05.2019; Ogledov: 3280; Prenosov: 107
Celotno besedilo (2,46 MB) |
209. Monte Carlo studies for the optimisation of the Cherenkov Telescope Array layoutA. Acharyya, Samo Stanič, Serguei Vorobiov, Lili Yang, Danilo Zavrtanik, Marko Zavrtanik, 2019, izvirni znanstveni članek Ključne besede: very-high energy gamma-ray astronomy, Cherenkov Telescope Array, array layout optimisation, Monte Carlo studies
Objavljeno v RUNG: 18.04.2019; Ogledov: 3050; Prenosov: 0
Gradivo ima več datotek! Več... |
210. Investigation of Aerosol Properties and Structures in Two Representative Meteorological Situations over the Vipava Valley Using Polarization Raman LiDARLonglong Wang, Samo Stanič, William Eichinger, Griša Močnik, Luka Drinovec, Asta Gregorič, 2019, izvirni znanstveni članek Opis: Vipava valley in Slovenia is a representative hot-spot for complex mixtures of different aerosol types of both anthropogenic and natural origin. Aerosol loading distributions and optical properties were investigated using a two-wavelength polarization Raman LiDAR, which provided extinction coefficient, backscatter coefficient, depolarization ratio, backscatter Ångström exponent and LiDAR ratio profiles. Two different representative meteorological situations were investigated to explore the possibility of identifying aerosol types present in the valley. In the first case, we investigated the effect of strong downslope (Bora) wind on aerosol structures and characteristics. In addition to observing Kelvin–Helmholtz instability above the valley, at the height of the adjacent mountain ridge, we found new evidence for Bora-induced processes which inject soil dust aerosols into the free troposphere up to twice the height of the planetary boundary layer (PBL). In the second case, we investigated aerosol properties and distributions in stable weather conditions. From the observed stratified vertical aerosol structure and specific optical properties of different layers we identified predominant aerosol types in these layers.
Ključne besede: aerosol structures, aerosol characterization, polarization Raman LiDAR, Vipava valley
Objavljeno v RUNG: 08.03.2019; Ogledov: 3879; Prenosov: 118
Celotno besedilo (3,11 MB) |
