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Measurements and modeling of air mass motion in the troposphere
Miha Živec, 2016, diplomsko delo

Opis: Throughout the history human race depended on weather, so one of the priorities for its survival was to understand weather patterns and to be able to forecast weather. With the development of powerful computers, atmospheric numerical methods and precision instruments for atmospheric monitoring, it is possible to predict weather with greater accuracy and for a longer period of time ahead. At the same time, we are able to gain improved understanding of physical processes that occur in the atmosphere and represent one of most important features in our world. This diploma thesis focuses on the lowest part of the atmosphere - troposphere only, as all weather occurs in the troposphere. Weather is a complete collection of momentary thermodynamic states in the atmosphere and is defined with thermodynamic variables and relations between them. The goal of this thesis is development and presentation of a new way to determine the direction and speed of air mass movement, based on the combination of passive and active remote sensing techniques. A lidar is being used to determine the range to an object, in our case a cloud, that can be used as a tracer in the air current. Simultaneously with lidar ranging of clouds that same clouds are being visually monitored in a series of optical photographs. Selecting and following the temporal evolution of distinct cloud features and their range allows us to calculate the speed of clouds. The performance of this method was tested on four cases in Feb. and Mar. 2016. Measurements were performed in Ajdovščina in different weather conditions. Along with remote sensing (infra-red lidar and optical cameras), ground measurements of wind at Ajdovščina were performed. Wind speeds and directions obtained from remote sensing were compared to atmospheric sounding data from Ljubljana and Udine at similar heights and performed within as small as possible time window. In all four cases remote sensing results for wind speeds and directions agree relatively well with atmospheric sounding. Deviations are expected to be primarily due to spatial and temporal mismatch between sounding and remote sensing measurements. Another source of uncertainties are the limitations of the present remote sensing method in the determination of the actual direction of the wind, however, theses limitations could be eliminated in the future by using an all-sky camera and vertical lidar configuration.
Najdeno v: ključnih besedah
Povzetek najdenega: ...on the combination of passive and active remote sensing techniques. A lidar is being used...
Ključne besede: remote sensing, wind, atmosphere
Objavljeno: 13.10.2016; Ogledov: 2490; Prenosov: 45
.pdf Polno besedilo (9,48 MB)

Study of the properties of air flow over orographic barrier
Maruška Mole, 2017, doktorska disertacija

Opis: 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.
Najdeno v: ključnih besedah
Povzetek najdenega: ...of the atmosphere can be obtained using remote sensing techniques. Contrary to vertical profile measurements...
Ključne besede: remote sensing, Vipava valley, wind properties, Bora, wind gusts, wind periodicity, tropospheric structures, Kelvin-Helmholtz waves
Objavljeno: 18.09.2017; Ogledov: 1388; Prenosov: 57
.pdf Polno besedilo (45,11 MB)

Longlong Wang, doktorska disertacija

Opis: The aim of the dissertation was to study aerosol loading distributions and properties over the Vipava valley, a representative hot-spot for complex mixtures of different aerosol types of both anthropogenic and natural origin. An infrared Mie and a two-wavelength polarization Raman lidar systems were used as main detection tools. The polarization Raman lidar, which provides the capability to extract the extinction coefficient, backscatter coefficients, depolarization ratio, backscatter Ångström exponent, lidar ratio and water vapor mixing ratio profiles, was itself designed, built and calibrated as a part of this thesis. Lidar data, combined with in-situ measurements, was used to determine detailed information on different aerosol types. Vertical profiles of aerosol mass concentration were extracted from the Mie lidar data taken in April 2016, where the in-situ measurements of aerosol size distribution and number concentration as well as aerosol absorption coefficient and black carbon mass concentration were used to estimate the mass extinction efficiency (MEE). Aerosol morphology and chemical composition determined by SEM-EDX on sampled particles were used for the identification of primary aerosol types. Two cases with different atmospheric conditions (long range mineral dust transport and local biomass burning) and different expected the dominant presence of specific aerosol types (mineral dust and soot) were investigated in more detail. They revealed significantly different aerosol properties and distributions within the valley, affecting radiative heat exchange. A more detailed investigation of aerosol properties throughout the troposphere in different atmospheric conditions was made possible by the two-wavelength polarization Raman lidar system, deployed in Ajdovščina (town of Vipava valley) from September 2017. Using its aerosol identification capabilities, based on particle depolarization ratio and lidar ratio measurements, it was possible to identify predominant aerosol types in the observed atmospheric structures, for example in different atmospheric layers in the case of the stratified atmosphere. Primary anthropogenic aerosols within the valley were found to be mainly emitted from two sources: individual domestic heating systems, which mostly use biomass fuel and traffic. Natural aerosols, transported over large distances, such as mineral dust and sea salt, were observed both above and entering into the planetary boundary layer. Backscatter contribution of each aerosol type was separated and the corresponding extinction contribution was derived from lidar observations.
Najdeno v: ključnih besedah
Povzetek najdenega: ...Vipava valley, aerosol distribution, aerosol characterization, lidar remote sensing, in-situ measurements, aerosol loading....
Ključne besede: Vipava valley, aerosol distribution, aerosol characterization, lidar remote sensing, in-situ measurements, aerosol loading.
Objavljeno: 23.10.2018; Ogledov: 251; Prenosov: 10
.pdf Polno besedilo (29,39 MB)

Retrieval of Vertical Mass Concentration Distributions—Vipava Valley Case Study
Miloš Miler, Janja Vaupotič, Luka Drinovec, Griša Močnik, William Eichinger, Klemen Bergant, Samo Stanič, Longlong Wang, Mateja Gosar, Asta Gregorič, 2019, izvirni znanstveni članek

Opis: Aerosol vertical profiles are valuable inputs for the evaluation of aerosol transport models, in order to improve the understanding of aerosol pollution ventilation processes which drive the dispersion of pollutants in mountainous regions. With the aim of providing high-accuracy vertical distributions of particle mass concentration for the study of aerosol dispersion in small-scale valleys, vertical profiles of aerosol mass concentration for aerosols from different sources (including Saharan dust and local biomass burning events) were investigated over the Vipava valley, Slovenia, a representative hot-spot for complex mixtures of different aerosol types of both anthropogenic and natural origin. The analysis was based on datasets taken between 1–30 April 2016. In-situ measurements of aerosol size, absorption, and mass concentration were combined with lidar remote sensing, where vertical profiles of aerosol concentration were retrieved. Aerosol samples were characterized by SEM-EDX, to obtain aerosol morphology and chemical composition. Two cases with expected dominant presence of different specific aerosol types (mineral dust and biomass-burning aerosols) show significantly different aerosol properties and distributions within the valley. In the mineral dust case, we observed a decrease of the elevated aerosol layer height and subsequent spreading of mineral dust within the valley, while in the biomass-burning case we observed the lifting of aerosols above the planetary boundary layer (PBL). All uncertainties of size and assumed optical properties, combined, amount to the total uncertainty of aerosol mass concentrations below 30% within the valley. We have also identified the most indicative in-situ parameters for identification of aerosol type.
Najdeno v: ključnih besedah
Povzetek najdenega: ...and mass concentration were combined with lidar remote sensing, where vertical profiles of aerosol concentration...
Ključne besede: valley air pollution, aerosol vertical distributions, lidar remote sensing, in-situ measurements, aerosol identification
Objavljeno: 09.01.2019; Ogledov: 179; Prenosov: 3
.pdf Polno besedilo (7,43 MB)

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