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Study of the properties of air flow over orographic barrier
Maruška Mole, 2017, doctoral dissertation

Abstract: Earth’s atmosphere is a complex system. All weather phenomena take place in its lowest layer, the troposphere, which is strongly influenced by human activities and the underlying surface orography. A good example of the influence the orography has on the behavior of air flows is the appearance of strong north-east downslope wind in Vipava valley, called Bora. Numerical models used to analyze flows in complex terrain need meteorological data both for setting the initial conditions and the verification of modeling results. Obtaining spatial distributions of meteorological observables can be challenging, especially in the case of strong winds, such as Bora, where traditional methods may be inadequate due to prohibitive wind speeds. In most cases, vertical properties of the atmosphere can be obtained using remote sensing techniques. Contrary to vertical profile measurements with traditional methods, remote sensing techniques do not require the measuring device to be placed within the flow and are therefore more appropriate for measurements in severe weather conditions such as strong winds. The aim of this thesis is a detailed analysis of wind and tropospheric structure properties in and above the Vipava valley in a variety of typical atmospheric conditions, including strong wind events. It employs a combination of high resolution wind and lidar data in addition to standard meteorological measurements. In Ajdovščina, there are four predominant wind directions, two of them directly connected to Bora. In the case of Bora, periodicity analysis of wind data from Ajdovščina yielded a range of possible wind gust periods between 1 and 7 minutes. The periods were not stable, with the periodogram less noisy for stable wind directions. Wavelike structures were found to be present in the troposphere in half of the investigated cases, regardless of the presence of Bora. In statically stable conditions, gravity waves propagated throughout the planetary boundary layer (PBL). In the case of Bora, the PBL experienced oscillations with periods between 1 and 2 minutes. A shear layer was present above the PBL, causing Kelvin-Helmholtz waves at its boundaries with periods ranging from 3 to 6 minutes. In some cases, periodic structures were observed above the shear layer as well, which were found to have longer periods than those within the PBL.
Keywords: remote sensing, Vipava valley, wind properties, Bora, wind gusts, wind periodicity, tropospheric structures, Kelvin-Helmholtz waves
Published in RUNG: 18.09.2017; Views: 6370; Downloads: 199
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Meritve hitrosti gibanja zračnih mas
Samo Stanič, Maruška Mole, Miha Živec, 2017, published scientific conference contribution

Abstract: V prispevku predstavljamo novo metodo merjenja smeri in hitrosti gibanja zračnih mas, ki temelji na kombinaciji aktivnega (lidarski sistem) in pasivnega (kamera) daljinskega zaznavanja atmosfere. S pomočjo lidarja smo določili razdaljo do oblakov, ki so služili kot sledilci v zračnem toku. Sočasno z lidarskimi meritvami smo fotografirali del neba, v katerega je bil usmerjen lidar. Iz meritev oddaljenosti oblakov ter njihovega premikanja smo izračunali hitrost potovanja oblakov in s tem tudi spodnjo mejo hitrosti zračne mase, ki je oblake nosila. Metodo merjenja hitrosti gibanja zračnih mas smo preizkusili na štirih testnih primerih v februarju in marcu 2016. Meritve so potekale v Ajdovščini v različnih vremenskih pogojih. Poleg naprav za daljinsko zaznavanje (lidar in optične kamere) smo za primerjavo uporabili tudi prizemne meritve vetra v Ajdovščini ter podatke vertikalne sondaže atmosfere v Vidmu in Ljubljani. Rezultati meritev vetra z daljinskim zaznavanjem se v vseh štirih opazovanih primerih relativno dobro ujemajo z rezultati sondaž, do odstopanj pa prihaja zaradi krajevnega in časovnega neujemanja sondaž z daljinskim zaznavanjem.
Keywords: daljinsko zaznavanje, veter, atmosfera
Published in RUNG: 10.02.2017; Views: 5131; Downloads: 0
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Lidar measurements of Bora wind effects on aerosol loading
Maruška Mole, Longlong Wang, Samo Stanič, Klemen Bergant, William Eichinger, Francisco Ocaña, Benedikt Strajnar, Primož Škraba, Marko Vučković, William Willis, 2017, original scientific article

Abstract: The Vipava valley in Slovenia is well known for the appearance of strong, gusty North-East Bora winds, which occur as a result of air flows over an adjacent orographic barrier. There are three revealing wind directions within the valley which were found to give rise to specific types of atmospheric structures. These structures were investigated using a Mie scattering lidar operating at 1064 nm, which provided high temporal and spatial resolution backscatter data on aerosols, which were used as tracers for atmospheric flows. Wind properties were monitored at the bottom of the valley and at the rim of the barrier using two ultrasonic anemometers. Twelve time periods between February and April 2015 were selected when lidar data was available. The periods were classified according to the wind speed and direction and investigated in terms of appearance of atmospheric structures. In two periods with strong or moderate Bora, periodic atmospheric structures in the lidar data were observed at heights above the mountain barrier and are believed to be Kelvin–Helmholtz waves, induced by wind shear. No temporal correlation was found between these structures and wind gusts at the ground level. The influence of the wind on the height of the planetary boundary layer was studied as well. In periods with low wind speeds, the vertical evolution of the planetary boundary layer was found to be governed by solar radiation and clouds. In periods with strong or moderate Bora wind, convection within the planetary boundary layer was found to be much weaker due to strong turbulence close to the ground, which inhibited mixing through the entire layer.
Keywords: Downslope wind Lidar observations Kelvin–Helmholtz waves Bora
Published in RUNG: 06.01.2017; Views: 5200; Downloads: 0
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Observations of atmospheric structures in the Vipava valley based on Lidar data
Maruška Mole, Longlong Wang, Samo Stanič, Asta Gregorič, Klemen Bergant, William Eichinger, Marko Vučković, 2016, published scientific conference contribution abstract

Keywords: lidar, atmosferske strukture, vremenske razmere
Published in RUNG: 03.05.2016; Views: 4870; Downloads: 0
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Evolution of the planetary boundary layer in the presence of fog and plume
Longlong Wang, Samo Stanič, Asta Gregorič, Klemen Bergant, Maruška Mole, Marko Vučković, 2016, published scientific conference contribution abstract

Keywords: lidar, vodna para, sipanje, GPS
Published in RUNG: 03.05.2016; Views: 5257; Downloads: 1
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Študij atmosferskih procesov v Vipavski dolini na podlagi razširjanja aerosolov
Maruška Mole, Longlong Wang, Asta Gregorič, Klemen Bergant, Luka Drinovec, Griša Močnik, Samo Stanič, Janja Vaupotič, Marko Vučković, 2016, published scientific conference contribution

Abstract: Vipavska dolina je geomorfološko dokaj zaprta, kar po eni strani omogoča pojav močne burje, po drugi strani pa ob stabilnih meteoroloških razmererah ugodne pogoje za kopičenje aerosolov znotraj prizemne mejne plasti. Poznavanje dinamike višinske porazdelitve aerosolov s sočasno uporabo prizemnih meritev omogoča raziskave lokalnih emisij aerosolov, transporta aerosolov na daljše razdalje ter značilnih atmosferskih struktur, ki se pojavijo v različnih vremenskih pogojih. Pri meritvah smo uporabili metode daljinskega zaznavanja z lidarjem, ki omogočajo opazovanje časovnega in prostorskega spreminjanja koncentracij aerosolov, ter točkovne meritve, ki omogočajo njihovo prepoznavanje in določanje njihovih lastnosti. Ugotovili smo, da je mogoče lidarske meritve uporabiti za študij vrste atmosferskih procesov in struktur v zelo različnih vremenskih pogojih. Opazili smo manjše konvekcijske strukture znotraj prizemne mejne plasti in gravitacijske valove nad njo. Meritve vsebnosti in lastnosti aerosolov pri tleh kažejo, da se lahko ob stabilnih atmosferskih pogojih v primerih povečanja lokalnih emisij njihove koncentracije hitro povečajo. Dinamiko in strukturo razširjanja aerosolov znotraj Vipavske doline bomo v prihodnje podrobneje raziskali s sočasnim prostorskim pregledovanjem z metodami daljinskega zaznavanja.
Keywords: aerosoli, atmosferski procesi, daljinsko zaznavanje, Vipavska dolina
Published in RUNG: 25.01.2016; Views: 6535; Downloads: 9
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