Measurements and modeling of air mass motion in the troposphere

diploma thesis

Miha Živec (Author), Samo Stanič (Mentor)

Abstract

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.

Keywords

remote sensing;wind;atmosphere;

Data

Language:	English
Year of publishing:	2016
Typology:	2.11 - Undergraduate Thesis
Publisher:	[M. Živec]
UDC:	52
COBISS:	4542971
Views:	6982
Downloads:	190
Average score:	0 (0 votes)
Metadata:

Other data

Secondary language:	Slovenian
Secondary title:	Meritve in modeliranje gibanja zračnih mas v troposferi
Secondary abstract:	Skozi zgodovino je bil človek vedno odvisen od vremena. Ena od prioritet za njegov obstoj je bilo poznavanje vremenskih vzorcev in sposobnost napovedovanja vremena. V zadnjih letih se lahko vreme z uporabo sodobnih merilnikov atmosferskih lastnost, numeričnih modelov in super-računalnikov napoveduje natančneje in za daljše časovno obdobje kot kadarkoli do zdaj. Hkrati se izboljšuje tudi razumevanje fizikalnega ozadja atmosferskih procesov, ki predstavljajo eno najpomembnejših lastnosti našega sveta. V diplomskem delu se omejimo na pojave v spodnji plasti atmosfere -- troposferi, v kateri potekajo vsi vremenski procesi. Pod pojmom vreme razumemo trenutno stanje in dogajanje v ozračju, ki ga je mogoče opisati s termodinamskimi vremenskimi spremenljivkami in zvezami med njimi. Ena glavnih značilnosti troposfere je gibanje zraka v horizontalni in vertikalni smeri. Za zanesljivo modeliranje in napovedovanje vremenskih dogajanj je torej pomembno čim boljše poznavanje stanja atmosfere, vključno z zračnimi tokovi, kar zmanjša napake pri modeliranju. Cilj diplomske naloge je predstavitev novega načina za merjenje smeri in hitrosti gibanja zračnih mas, ki temelji na kombinaciji aktivnega in pasivnega daljinskega zaznavanja stanja atmosfere. S pomočjo lidarja se določi razdalja do objekta, ki služi kot sledilec v zračnem toku. V tem primeru so bili sledilci kar oblaki. Sočasno z lidarskimi meritvami se fotografira del neba, v katerega je usmerjen lidar. Na fotografijah se poišče izrazite dele oblakov, ki jim je mogoče slediti na več zaporednih posnetkih. Iz meritev oddaljenosti sledilca ter njegovega premikanja izračunamo hitrost potovanja oblaka in s tem tudi hitrost zračne mase, ki oblak nosi. 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 uporabili tudi prizemne meritve vetra v Ajdovščini ter podatke vertikalne sondaže atmosfere v Udinah in v Ljubljani. Rezultati meritev vetra z daljinskim zaznavanjem se v vseh štirih opazovanih primerih relativno dobro ujemajo z rezultati sondaže. Do odstopanj prihaja zaradi krajevnega in časovnega neujemanja sondaž z daljinskim zaznavanjem ter zaradi omejitev metode z daljinskim zaznavanjem pri določevanju dejanske smeri vetra. Opažene omejitve metode je mogoče odpraviti z uporabo vsenebnih kamer ter vertikalnih lidarskih meritev.
Secondary keywords:	diplomske naloge;daljinsko zaznavanje;veter;atmosfera;
URN:	URN:SI:UNG
Type (COBISS):	Bachelor thesis/paper
Thesis comment:	Univ. of Nova Gorica, School of Science
Pages:	VIII, 36 str.
ID:	9176594