Repository of University of Nova Gorica

Show document
A+ | A- | Help | SLO | ENG

Title:Study of the properties of air flow over orographic barrier
Authors:ID Stanič, Samo (Mentor) More about this mentor... New window
ID Bergant, Klemen (Mentor) More about this mentor... New window
ID Mole, Maruška (Author)
Files:.pdf Maruska_Mole.pdf (45,11 MB)
MD5: 3AB37619026D4C14454B91AD8D4FDFCD
 
Language:English
Work type:Doctoral dissertation
Typology:2.08 - Doctoral Dissertation
Organization:FPŠ - Graduate School
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
Place of publishing:Nova Gorica
Year of publishing:2017
PID:20.500.12556/RUNG-3270-b6fe5d60-5560-7bf4-fbdb-03e2ecd934dd New window
COBISS.SI-ID:4916219 New window
NUK URN:URN:SI:UNG:REP:GCMQKOIH
Publication date in RUNG:18.09.2017
Views:8354
Downloads:215
Metadata:XML DC-XML DC-RDF
:
MOLE, Maruška, 2017, Study of the properties of air flow over orographic barrier [online]. Doctoral dissertation. Nova Gorica. [Accessed 22 April 2025]. Retrieved from: https://repozitorij.ung.si/IzpisGradiva.php?lang=eng&id=3270
Copy citation
  
Average score:
0.5
1
1.5
2
2.5
3
3.5
4
4.5
5
(0 votes)
Your score:Voting is allowed only for logged in users.
Share:Bookmark and Share


Hover the mouse pointer over a document title to show the abstract or click on the title to get all document metadata.

Secondary language

Language:Slovenian
Title:Lastnosti zračnega toka ob prehodu čez orografsko oviro
Abstract:Gorske pregrade močno vplivajo na vreme in podnebje, ki se pojavlja v njihovi okolici. Zaradi dviganja zračnih mas čeznje pogosto povzročajo padavine na svoji priveterni in močne vetrove na zavetrni strani. Značilen primer vetra, ki nastane zaradi prelivanja hladnih zračnih mas čez planote Trnovskega gozda, je burja v Vipavski dolini. Lastnosti burje tako kot tudi zračnega toka, ki jo povzroča, je težko določiti, saj klasične meritve z meteorološkimi baloni v vetrovnih razmerah ne omogočajo zajema navpičnih presekov nad izbrano točko. Težave so tudi z opisom sunkov vetra ter njihovo periodiko, saj so najkrajši časovni intervali standardnih meritev vetra na meteoroloških postajah Agencije Republike Slovenije za okolje 10 minut. Disertacija predstavlja podrobno študijo vetrovnega dogajanja v Vipavski dolini, ki temelji na 3-minutnih meritvah vetra vzdolž Vipavske hitre ceste, 10-sekundnih meritvah hitrosti vetra v dveh linijah, pravokotnih na gorsko pregrado med Vipavo in Ajdovščino, ter 1-sekundnih meritvah vetra v Ajdovščini. Podatki, zbrani v letih 2012 ter 2015-2016, omogočajo oceno vpliva orografije na zračne tokove znotraj Vipavske doline, spremljanje razvoja hitrosti vetra po pobočju navzdol, ter analizo periodičnega dogajanja, povezanega s sunkovitosto burje. Troposferske stukture, opažene nad dolino z uporabo mobilnega lidarskega sistema Univerze v Novi Gorici, dopolnjujejo opis dogajanja, saj omogočajo vpogled v dinamiko zračnega toka v prizemni mejni plasti in nad njo. V Ajdovščini se burja pojavlja kot severo- ali jugovzhodnik z značilnimi pulzacijami hitrosti vetra s periodami med 1 in 7 minut. Periodične strukture se pojavljajo tudi višje nad tlemi, tako v primeru burje kot tudi sicer. Med burjo smo v primeru vetrovnega striga opazili Kelvin-Helmholtzove valove s periodami med 3 in 6 minut na mejah strižne plasti, valovanja pod in nad strižno plastjo pa so imela periode med 1 in 2 minuti za spodnjo ter nad 3 minute za zgornjo plast. V primeru stabilne atmosfere smo prav tako opazili periodične strukture, ki so bile posledica gravitacijskih valov.
Keywords:daljinsko zaznavanje, Vipavska dolina, veter, burja, sunki vetra, periodika vetra, troposferske strukture, Kelvin-Helmholtzovi valovi


Back