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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
321

A climatology of particulate pollution in Christchurch

Appelhans, Tim January 2010 (has links)
The research presented in this thesis provides a quantitative analysis of atmospheric influences on particulate matter pollution in Christchurch across a wide range of spatial and temporal scales. A complex interaction of low level flow characteristics that form in response to local and regional features of complex terrain, together with an urban setting that is characterised by low density housing, mostly comprised of single storey dwellings that are poorly insulated, regularly leads to nocturnal smog events during winter in Christchurch. Provided synoptic flow is weak, the above mentioned flow interaction promotes flow stagnation over the city, when nocturnal katabatic drainage flows and day-time north-easterly on-shore winds converge over the city. Additionally, undercutting of the density currents promotes highly stable atmospheric stratification close to the surface, so that, in combination, both horizontal and vertical air movement is suppressed. As particulate emission release from solid fuel burning for home heating coincides with this poor atmospheric dispersion potential, particle concentrations can increase substantially so that national air quality guidelines are regularly exceeded during winter in Christchurch. At the core of this thesis is a classification based approach that examines the day-to-day probabilities of breaches of the national air quality guideline for PM over the last decade at a single location in Christchurch as a result of variations in meteorological conditions alone. It is shown that, based on variations in temperature and wind speed, up to 85% of exceedence occurrence can be explained. From this, concentration trends over time, when meteorological variability is kept to a minimum, are assessed and evidence is found that recent regulatory measures to enhance air quality are beginning to show positive effects. Atmospheric processes that control pollution dispersion on the mesoscale are investigated through means of atmospheric numerical modelling in a novel approach that assimilates observational climatic wind field averages to drive low level flow for two idealised case studies. It is shown that this approach is able to reproduce the observed diurnal concentration patterns very well and that much of these patterns can be attributed to mesoscale circulation characteristics and associated atmospheric dispersion potential, namely flow stagnation and recirculation of contaminants. When timing of stagnation and subsequent recirculation is such that it occurs within a few hours after peak emission release, concentration increase is enhanced and dilution is delayed, thus severely exacerbating the problem. Links between exceedence probabilities and synoptic situations that favour the degradation of air quality are established and various synoptic transition scenarios are examined with regard to local air quality. The progression of anticyclones across the country is identified to be the dominant synoptic control mechanism and it is shown that latitudinal variation in the progression path determines the extent of expected exceedence probability. On interdecadal hemispheric scales, it is found that a particular combination of local and synoptic atmospheric conditions that favours air quality degradation, shows a re-occurring pattern of frequency maxima (and minima) with a periodicity of approximately 14 - 16 years. For the synoptic part of this interdecadal variability, a close relationship to Southern Hemispheric pressure anomalies in high latitudes is revealed. Finally, for verification of the combined findings and to assess their prediction capability, a validation case study is given which shows that the applied methodology is able to capture day-to-day variations in pollution levels with acceptable (statistically significant) accuracy.
322

Aeolian dust emission, transport and deposition in Western Libya

Elatrash, Mokhtar Salem January 2004 (has links)
Of numerous aeolian studies around the world, few have been dedicated to dust trapping in the Saharan regions and none is known in Libya. This research aims to explore the extent of dust activities in the western part of Libya, the main factors that influence dust entrainment and deposition, the likely regional emission sources transporting aerosol to this part of the country and ultimately to establish base line information in space and time based on a study area larger than the size of the UK. Dust trapping was carried out at thirty sites on a monthly basis starting from the beginning June 2000 until the end of May 2001. A physical characterization of 274 aeolian sediments were based on grain size distribution analysis and the mineral composition was based on XRD testing of 24 dust samples taken from extreme locations near the Mediterranean Sea and about 800 km inland. An assessment of dust emissions within the area of study, the vertical deposition rates in relation to The Total Ozone Mapping Spectrometer (TOMS) data have been investigated. Moreover, an attempt identify potential Saharan dust emission sources that have impacted the study area has also been made utilizing TOMS data. The area of study has been divided into three regions northern, central and southern according to the dominant factors controlling mobilization of dust particles on the bed surface. This study concludes that deposition rates in the northern coastal region are largely dominated by human activities. Rates in the central region were strongly affected by topographic irregularities whereas in the south deposition rates were less affected by topography and anthropogenic activity. However, deposition rates and particle size distributions are strongly controlled by wind regimes and correlate with the average atmospheric temperatures. Local sediments seem to be strongly affected by saltating particles in most of the study area and no evidence of long range aerosol emission from western Libya was found. Nevertheless, fine dust (<10 gm) is wide spread in the local atmosphere, however it is more pronounced during late spring and summer. TOMS data and the prevailing wind directions reveal that the depressions of the Libyan Desert and the Bodele Depression in Chad were the main sources of aerosol transported over the study area during the highest months of emission, transport and deposition, July and April. It is hoped that this baseline information can pave the way for future studies on dust impacts on soil fertility, human health, desertification, climate change and the validation of present day computer models.
323

Climate and heat exchange in the oceanic region adjacent to Oregon

Lane, Robert Kenneth 20 April 1965 (has links)
The climate and the exchange of heat between atmosphere and ocean are examined in a region adjacent to Washington and Oregon, and in two sub-regions adjacent to Oregon. The sub-regions are chosen such that one contains the nearshore upwelling region and the other borders it on the seaward side. The data (ship weather observations, 1953 to 1962) reveal the general seasonal variation of climatic factors in the regions studied and the effects of the nearshore upwelling of cold water on the climate over the coastal ocean region and the adjacent coastal land mass. In the nearshore sub-region, summer values of temperature (air, wet bulb, and sea surface) are lower than those to seaward, but winter values are higher inshore than to seaward. The effects of these differences, and of other factors, on the heat exchange processes are examined with the use of empirical equations. It is seen that the processes of evaporation and conduction are suppressed considerably and net long wave radiation is slightly suppressed in the upwelling region during the summer. The effects of the reduction of heat loss to the atmosphere in the summer upwelling region on the climate of coastal Oregon are seen to be a slight reduction of air temperatures and, despite reduced evaporation, a very slight increase of relative humidity. Monthly means of daily net heat exchange between the sea and the atmosphere are examined and correlated with the difference between monthly means of the heat used per day in the oceanic evaporation process and the monthly means of daily totals of heat estimated to be used in the evaporation from a shallow pan under climatic conditions identical to those accompanying the net heat exchange and oceanic evaporation. / Graduation date: 1965
324

Seasonality in human mortality a demographic approach /

Rau, Roland. January 2007 (has links)
Thesis (doctoral) - Universität, Rostock, 2005. / Includes bibliographical references (p. [187]-214).
325

Assessment and potential adjustments to the snow-related algorithms in BIOME-BGC, v. 4.2

DeWire, Deana Ann. January 2008 (has links)
Thesis (M.A.)--University of Montana, 2008. / Title from title screen. Description based on contents viewed May 6, 2009. Includes bibliographical references (p. 80-86).
326

Examining the impacts of dynamic downscaling method and vegetation biophysical processes on the South American regional climate simulation

De Sales, Fernando Henrique, January 2006 (has links)
Thesis (Ph. D.)--UCLA, 2006. / Vita. Includes bibliographical references (leaves 189-201).
327

High-resolution climate variable generation for the Western Cape /

Joubert, Sarah Joan. January 2007 (has links)
Thesis (MSc)--University of Stellenbosch, 2007. / Bibliography. Also available via the Internet.
328

Seasonal and interannual variability of tropical diurnal warming of sea surface temperatures

Weitlich, Derrick Karl. Clayson, Carol Anne. January 2005 (has links)
Thesis (M.S.)--Florida State University, 2005. / Advisor: Dr. Carol Anne Clayson, Florida State University, College of Arts and Sciences, Dept. of Meteorology. Title and description from dissertation home page (viewed June 16, 2005). Document formatted into pages; contains xii, 82 pages. Includes bibliographical references.
329

Seasonal variation in disease methodology with application to Pennsylvania data

Portnoy, Alfhild Vold, January 1944 (has links)
Thesis (Ph. D.)--University of Pennsylvania, 1942. / Reproduced from type-written copy. "References" at end of chapters II-Iv.
330

Fluctuations in hurricane landfall frequency along the east coast of Florida as a function of regional climate

Wood, Jefferson. Elsner, James B. January 2004 (has links)
Thesis (M.S.)--Florida State University, 2004. / Advisor: Dr. James Elsner, Florida State University, College of Social Sciences, Dept. of Geography. Title and description from dissertation home page (viewed Jan. 18, 2005). Includes bibliographical references.

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