Dissertations / Theses on the topic 'Meteorology Australia'

The Global Positioning System (GPS) of navigation satellites was first developed for global navigation and position determination purposes. Signals from satellites are delayed by the Earths neutral atmosphere on propagating to ground-based receivers, termed the tropospheric delay. Although an unwanted term for precise positioning, the tropospheric delay may be converted to atmospheric water vapour, which is a vital parameter for weather forecasting.This research investigates the optimum GPS processing strategy to estimate atmospheric water vapour derived from ground-based GPS receivers particularly in the Australian region. For this purpose, GPS data observations from GPS permanent stations across Australia, mainly from the Australian Regional GPS Network, will be processed using scientific GPS software in post-processed mode and near real-time mode.This research shows that by applying high accuracy GPS data processing, the tropospheric delay could be estimated precisely. The quality of GPS data processing is indicated by the station coordinates repeatability since the coordinates can gauge at least a coarse assessment of the ability of the processing method to estimate the tropospheric delay.The precipitable water can be estimated from the wet component after separating the tropospheric delay into dry and wet components. High accuracy GPS data processing is dependent on the best choice of processing strategies, and the correct application of error-correction models and a priori constraints. This research finds that the GPS- PW estimation agrees with Radiosonde-PW estimation with an average of standard deviation at 2.5mm level for post-processed strategy and 2.8mm for near real-time strategy. The standard deviation of tropospheric parameter estimates is 1.1mm for post-processed strategy and 1.5mm for near real-time strategy.

The Global Positioning System (GPS) of navigation satellites was first developed for global navigation and position determination purposes. Signals from satellites are delayed by the Earths neutral atmosphere on propagating to ground-based receivers, termed the tropospheric delay. Although an unwanted term for precise positioning, the tropospheric delay may be converted to atmospheric water vapour, which is a vital parameter for weather forecasting.This research investigates the optimum GPS processing strategy to estimate atmospheric water vapour derived from ground-based GPS receivers particularly in the Australian region. For this purpose, GPS data observations from GPS permanent stations across Australia, mainly from the Australian Regional GPS Network, will be processed using scientific GPS software in post-processed mode and near real-time mode.This research shows that by applying high accuracy GPS data processing, the tropospheric delay could be estimated precisely. The quality of GPS data processing is indicated by the station coordinates repeatability since the coordinates can gauge at least a coarse assessment of the ability of the processing method to estimate the tropospheric delay.The precipitable water can be estimated from the wet component after separating the tropospheric delay into dry and wet components. High accuracy GPS data processing is dependent on the best choice of processing strategies, and the correct application of error-correction models and a priori constraints. This research finds that the GPS- PW estimation agrees with Radiosonde-PW estimation with an average of standard deviation at 2.5mm level for post-processed strategy and 2.8mm for near real-time strategy. The standard deviation of tropospheric parameter estimates is 1.1mm for post-processed strategy and 1.5mm for near real-time strategy.

The observations made near Grahamstown (33 .3°S, 26.5°E), South Africa and Adelaide (34.5°S, 138.5°E), Australia over the years 1987 to 1994 are used to study the dynamics of the mesosphere and lower thermosphere (ML T) region with a focus on ∼ 90 km altitude. In particular this thesis deals with on the atmospheric mean flow and the solar diurnal and semi diurnal oscillations with a view to (i) deducing their patterns at the two sites, (ii) comparing the dynamic structures observed at the two sites with special emphases on longitudinal variations, and (iii) putting these observations in a global context by comparing with other ground-based observations, satellite observations and numerical simulations. The main findings are summarised below. The mean flow and the tides at Grahamstown and Adelaide are characteristically variable at planetary time scales. Wavelet spectral and multiresolution analyses reveal that the dominant planetary oscillation is the quasi-16-day oscillation. However, no apparent correlation in the 16-day waves of the mean flow, the diurnal tide and the semidiurnal tide was found. The short-term fluctuations were also investigated using complex demodulation and bispectral techniques and it was found that some of the observed variations in tides could be due to non-linear wave-wave interactions. The long-term trends of the mean flow and tides show patterns that are in broad agreement with theory, results from elsewhere (ground-based and satellite) and the results of the Global-Scale Wave Model and various models by Portnyagin and others. In general the mean flow, the amplitudes and phases of both tides were found to exhibit seasonal and interannual variations which are thought to be related to various factors including (i) changes in the atmospheric mean environment, (ii) thermotidal forcing (iii) gravity wave effects, (iv) planetary scale influence, (v) long-term (e.g. quasi-biennial oscillation) modulation, and (vi) solar activity. There are significant longitudinal differences in the dynamic structure between Grahamstown and Adelaide. More especially, Grahamstown tends to have stronger mean flow and tidal activity than Adelaide. For tides, these differences are thought to be partly due to nonmigrating tidal modes but, in general, migrating modes were found to be dominant.

Thesis (Ph.D.)--University of Western Sydney, Hawkesbury, 2001.
A thesis submitted to the Faculty of Environmental Management and Agriculture, University of Western Sydney, in fulfilment of the rquirements for the degree of Doctor of Philosophy, 2001. Bibliography : p. 252-276.

California is headed into its fifth consecutive year of drought, and climate change is expected to bring more frequent and severe droughts to the state. The state’s water supply is susceptible to drought as seen from the effects of the current dry period. Besides the clear impacts of drought, there are less obvious environmental, economic, and social costs, such as land subsidence from groundwater overdraft, and the consequences of urban tree and green space loss. As a uniquely climate-independent source, desalinated water can stabilize California’s water supply and lessen some of these drought-related impacts. Although seawater desalination is touted as the most costly and energy-intensive method for augmenting water supply, if implemented in a feasible manner, the technology provides a range of positive benefits for drought-prone California in the long term. This thesis analyzes the economic and environmental costs of using desalination to mitigate the effects of drought in California. The thesis explores both Australian and Californian desalination facilities as case studies for evaluating the benefits and impacts of using different methods of desalination, in an effort to determine which method would be the most beneficial for securing California’s water supply. It concludes that lower-capacity, flexible desalination facilities would be useful along California’s coast, under some conditions. By generating a supply of desalinated water for coastal communities, more water from the state and federal water projects could be redirected to agricultural regions and inland communities that suffer the most from dry spells, and thereby lessen a number of drought-related environmental, economic, and social consequences.

Aquest treball es basa en les dades recollides al llarg de quatre campanyes de camp a l'Illa de Lívingston (Shetland del Sud. Antàrtida). L'objectiu principal és donar una visió coherent de la geologia del conjunt de l'illa, dins del seu marc geològic regional. La tesi comprèn (1) una síntesi geològica regional, (2) una compilació de dades sobre la geologia mesozoica a quaternària de l'Illa de Livingston i (3) una discussió de diversos punts clau de l'evolució geològica, amb especial èmfasi en la geomorfologia i la història quaternària. Els resultats més importants els sintetitzem a continuació:

L'Illa de Lívingston es divideix en diversos blocs tectònics. Les falles que separen els diferents blocs estan directament relacionades amb l'obertura del rift neògen de Bransfield. La tectònica de blocs influencia les variacions espacials en la intensitat d'erosió, l'aflorament de nivells més o menys profunds de la successió estratigràfica i. conjuntamente amb l'erosió diferencial, la distribució de les unitats fisiogràfiques.

Les plataformes d'erosió marina que es troben fins a una altitud de 120 m tenen una edat de Miocè inferior a Pleistocè. Aquestes plataformes s'han pogut formar únicament durant els estatges interglacials o durant períodes interglacials anteriors, quan el substrat es trobava parcialment descobert de gel i era susceptible a ser afectat pels processos d'erosió marina.

Les Illes Shetland del Sud, probablement han experimentat aixecament tectònic des dels inicis de l'obertura del rift de Branstield. L'aixecament tectònic no ha superat la velocitat
nutjana de 0.4 m/ka. A aquest aixecament tectònic relativament lent, l'arxipèlag ha estat afectat per altres moviments verticals d'orígen glàcio-isostàtic, molt més ràpids, associats a les fluctuacions glacials del Quaternari i del Terciari superior.

Durant el Darrer Màxim Glacial (al voltant de 21-18 ka B.P.), el gruix màxim de glaç a 1'Illa de Livingston probablement se situava entre 500 i 700 m. amb la qual cosa el glaç es trobava en contacte amb el substrat rocós fins a una profunditat de més de 400 m per sota del nivell del mar actual. Aquesta reconstrucció és compatible amb la presència d'un únic casquet glacial que hauria recobert el conjunt de l'arxipèlag de les Shetland. Si el temps de desglaçament proposat per la zona de la Peninsula Antàrtica és correcte (al voltant de 10 ka B.P.), el nivell de màxima inundació durant l'Holocè no hauria superat els 25-30 m. El desglaçament de l'arxipèlag i de la Península Antàrtica ha produït un aixecament glàcioisostàtic des de 10 ka B.P. L'emersió resultant ha permès la sedimentació de les platges aixecades Holocenes. Aquest model evolutiu implica que les platges situades a més de 30 m d'altitud sobre el nivell del mar actual han de ser pre-Holocenes, que es van haver de sedimentar durant algun període interglacial pleistocè i que han d'haver-se preservat parcialment, malgrat haver estat cobertes pel gel durant una o més glaciacions.

El registre glacial a l'Illa de Livingston permet de reconèixer un mínim de quatre fases glacials. Les dues fases glacials més antigues tenen una edat superior a 6.000 a B. P. i probablement registren fases d'estabilització o reavenç glacial associades al darrer màxim glacial o a la deglaciació posterior. Les dues fases glacials més recents són posteriors a 720 ka B.P. i s'inclouen dins de la Petita Edat del Gel.
Livingston Island is divided into several tectonic blocks. Faults bounding these blocks are directly related to opening of the Neogene Bransfield rift Tectonic block movements influence the spatial variations in erosion intensity, the outcrop of deeper or shallower stratigraphic levels and, together with differential erosion, the distribution of physiographic units.

Marine erosion platforms located at around 120 m and below have an early Miocene to late Pleistocene age. Platforms could only have been cut during interglaciations or nonglacial periods, when the substrate was locally free of ice and susceptible lo modification by marine processes. The South Shetland Islands probably underwent tectonic uplift after the first stages in the evolution of Bransfield rift. The tectonic uplift was produced at an average of less than 0.4 m/ka. Superimposed on this relatively slow tectonic uplift movement, the archipelago has been affected by other much faster vertical movements of glacio-isostatic origin, associated with Quatenary and late Tertiary glacial fluctuations.

During the Last Glacial Maximum (around 21 to 18 ka), Ice on Livingston Island probably had a maximum thickness of about 500 to 700 m and was grounded at depths of more than 400 m below present sea level, which is consistent with a single ice cap covering the whole central South Shetland Islands. If the assumed timing of deglaciation in the South Shetland Islands and the Antarctic Peninsula is correct, the maximum Holocene inundation would not have been 25 to 30 m. Deglaciation of the archipelago and the Antarctic Peninsula has produced glacio-isoslatic uplift since 10 ka BP. The resulting emergence allowed deposition of the Holocene raised beaches. This evolutive model implies that beaches or residual beaches above 30 m must have been deposited during interglaciations prior to the Holocene and must have been partially preserved in spite of being covered by ice during one or more glaciations. Several glacial phases are recognised from at least 6.4 ka BP to Present. We distinguish two recent glacial phases, at 720-330 years BP and at 300 years BP to Present.

A high quality, historical surface air temperature data set is essential for the reliable investigation of climate change and variability. In this study, such a data set has been prepared for Australia by adjusting raw mean annual temperature data for inhomogeneities associated with station relocations, changes in exposure, and other problems. Temperature records from long-term stations were collaborated from the set of all raw data held by the Australian Bureau of Meteorology. These long-term records were extended by combining stations and manually entering previously unused archived temperature measurements. An objective procedure was developed to determine the necessary adjustments, in conjunction with complementary statistical methods and station history documentation. The objective procedure involved creating a reference time series for each long-term station, from the median values at surrounding, well-correlated stations. Time series of annual mean maximum and mean minimum temperatures have been produced for 224 stations, and the adjusted dataset has been made available to the research community. The adjusted data are likely to be more representative of real climatic variations than raw data due to the removal of discontinuities. The adjusted data set has been compared with previously used temperature data sets, and data sets of other parameters. The adjusted data set provides adequate spatial coverage of Australia back to 1910. Additional adjusted data are available prior to this date at many stations. Trends in annual mean maximum, minimum, the mean of the maximum and minimum, and the range between the maximum and minimum, have been calculated at each site. Maximum and minimum temperatures have increased since about 1950, with minimum temperatures increasing faster than maximum temperatures.

This thesis presents three essays on the analysis of historical meteorological data in Australia. The Australian Bureau of Meteorology has established a network of more than one thousand stations across Australia that have recordings dating from early last century, resulting in a large dataset of meteorological records. These data provide important information on the dynamics of the Australian climate system and systematic investigation using these data can help us to better understand our climate and prepare for possible changes. The purpose of this thesis is to develop models and methods to analyse such meteorological data from a statistical perspective. In Chapter 2, a spatia-temporal model is developed based on monthly average temperature data at 177 locations in south-eastern Australia over 40 years. Guided by a preliminary analysis, a model with components dealing with spatial varying mean and seasonality, short-term and long-term temporal trends is built, and the space-time interaction is modelled by the kernel-convolution method. It is shown that the temperature has become warmer in most of the south-eastern Australia during the period under investigation. In Chapter 3, a new duration-dependent Hidden Markov Model is proposed as an extension to the Hidden Markov Model (HMM) and Non-homogeneous Hidden Markov Model (NHMM) which assumes that the transition probabilities are either constant or only depend on some independent variables. The possibility of duration-dependent effects is formally considered in this chapter where the transition probabilities are allowed to be explicitly correlated to duration - how long the hidden system has been in the current state. This approach is used to model the amount of daily rainfall amount at 5 locations in Darwin, Northern Territory. For data arising from climate phenomenon, such as the temperature and rainfall data considered here, it is common for outliers to be present. The presence of outliers could unduly influence the results of any analysis that are conducted and make conclusion non-robust. But it is often difficult to detect them simultaneously because of the masking effect. Motivated by this problem, a general method is proposed in Chapter 4 for identifying multiple influential observations in regression models. The ability of this method is tested and illustrated by both a thorough simulation and several examples.

Predicting where and how a fire will burn is critical information for mitigating the impacts of bushfires and minimising risk at fuel reduction burns. Firefighter entrapments and fatalities occur mostly at fires that display rapid changes or fluctuations in fire activity. In this thesis, I explore several of the factors that lead to rapid changes in fire behaviour. Understanding these factors is necessary in order to produce accurate fire predictions, which are critical for fire-fighter safety and effective operations. Weather is a primary driver of fire activity; consequently, meteorological information is a key input for anticipating fire behaviour. At present, weather forecasts focus on near-surface conditions; but fires and the atmosphere are three dimensional, and dynamical interactions occur that can have a dramatic influence on fire behaviour. However, these fire-atmosphere interactions are poorly understood due to their complex nature and the difficulty of collecting observational data from a bushfire. In order to further understanding of dynamical interactions between a fire and the surrounding atmosphere, we have simulated three Australian fires where unexpected fire activity occurred, using the coupled fire-atmosphere model WRF and SFIRE. The coupled simulations have been run in feedback on and feedback off mode in order to assess the impact that the fires have on their surrounding atmosphere. The results show significant changes to the mesoscale atmospheric structure as result of the energy released by the fire. Computational fire behaviour models are being used by fire managers in real time and this use will grow in the future. The question is, given we know that fires affect the surrounding atmospheric flow; what weather inputs should the fire models of the future use? The Australian fire science community is currently presented with the opportunity and the challenge to design, develop, and implement fire behaviour simulation models that contain appropriate and comprehensive meteorological inputs. The results presented in this thesis are thought provoking for the current approach to fire weather forecasts and for the use and development of computational fire simulations in the future.
Thesis (Ph.D.) -- University of Adelaide, School of Mathematical Sciences, 2014

Thesis (M.S.)--Florida State University, 2005.
Advisor: Dr. Henry E. Fuelberg, Florida State University, College of Arts and Sciences, Dept. of Meteorology. Title and description from dissertation home page (viewed Sept. 27, 2005). Document formatted into pages; contains ix, 42 pages. Includes bibliographical references.