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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.


BEN-DAVID, AVISHAY. January 1986 (has links)
The amount of information (types of solutions, accuracy and moments of the solution) about tropospheric rural aerosol size distribution that can in theory be obtained from backscattered measurements, without using any additional information about the anticipated solution, has been discussed. In practice, additional assumptions (constraints) must be used to solve for aerosol size distribution. The inferred solution reflects those assumptions and is therefore not objective. The quality of the solution depends on the applicability of the constraints to the given problem. A library of pseudo-empirical functions is used to form a set of orthogonal basis functions. It is assumed that any unknown aerosol size distribution may be constructed from a linear sum of these basis functions. The problem then becomes one of solving for the unknown coefficients of the basis functions. A solution with a smoothing constraint and a positivity constraint has been developed. Results of the method, when backscattered radiation is used as measurements, are presented. Discussion on the limitations of the method and the effects upon the solution of the different assumptions that are used is given. Some possible uses of the solution are considered.


Promyarat, Suporn. January 1982 (has links)
No description available.

Spectroscopic studies of atmospherically relevant acid hydrates

Nash, Karen January 2000 (has links)
No description available.

The solid state speciation and sea water solubility of elements in marine aerosols

Lin, F-J. January 1988 (has links)
No description available.

The atmospheric chemistry of extremely concentrated solutions

Clegg, S. L. January 1986 (has links)
No description available.

Extension of the constrained ratio approach to aerosol retrievals from elastic-scatter and high spectral resolution lidars

McPherson, Christopher J., Reagan, John A. 23 August 2016 (has links)
A methodology is presented, by which atmospheric aerosol retrievals from a standard, elastic-scatter, lidar can be constrained by using information from coincident measurements from a high spectral resolution lidar (HSRL) or Raman lidar at a different wavelength. As high spectral resolution or inelastic-scattering lidars are now being incorporated coaxially into instruments with traditional, elastic-scatter channels at different wavelengths, a standard approach is needed to incorporate or fuse the diversity of spectral information so as to make maximal use of the aerosol measurements made from the elastic-scatter channel or channels. The approach is evaluated through simulation and with data from the NASA Langley Research Center Airborne HSRL instrument. The generality and extensibility of the method is also explored and discussed in the context of aerosol modeling. (C) The Authors. Published by SPIE under a Creative Commons Attribution 3.0 Unported License.

The distribution of aerosol and trace gases in the lower troposphere over South Africa

Burger, Roelof Petrus January 2016 (has links)
A thesis submitted to the Faculty of Science, University of the Witwatersrand, Johannesburg, in fulfilment of the requirements for the degree of Doctor of Philosophy. September 2016. / Numerous studies on the sources, transport and fates of criteria air pollutants and greenhouse gases have been done in southern Africa. However, debate on the priority pollutants and areas of concern continue despite a growing national air quality monitoring network. This study attempts a novel approach to characterise sources and ambient air quality over major industrial and urban areas using a single suite of instrumentation to provide information to improve management of air quality. Over 200 hours of data were collected from an airborne platform. Another 5 ground-based campaigns characterised sources and areas out of reach of the aircraft. The central aim of this study is to prioritise sources and areas of concern with regards to air quality management, using a mobile platform. This complements other modelling and spatial assessments and provides in situ validation for many contemporary debates. The specific aims were to characterise major anthropogenic sources; estimate the state of air quality; investigate the vertical distribution of pollutants; and prioritise sources and areas of concern for effective air quality management in South Africa. The research has delivered many original contributions to the body of knowledge of air quality over South Africa. These findings can be divided into spatial and temporal relationships between sources and receptors, characterising source contributions and understanding the contribution of atmospheric emissions. High resolution measurements show that spatial scales of prominent atmospheric plumes are much smaller than current remote sensing estimates.This underscores the difficulty of accurately assessing environments with diverse, clustered sources and complex meteorology through modelling studies and satellite based remote sensing. The current conceptual model of absolute stable layers is biased because of limited data availability where a limited number of levels are reported. At least 60 levels should be reported in soundings to study absolutely stable layers. The inclusion of the standard reporting levels, (850 hPa, 700 hPa, 500 hPa and 300 hPa), further biases the detection of atmospheric stable layers. The number of observed persistent levels change in number and character when these are omitted from the analysis. Numerous vertical profiles further show that the thermodynamic model of stability as the main driver of stratification is oversimplified, especially close to source regions where different pollutants are observed to peak at different levels unrelated to absolutely stable layers. This suggests that the original buoyancy which is governed by the release temperature, exit velocity and height are important drivers for the stratification of pollutants. The overall conclusion is made that a small team with a set of regular instrumentation can prioritise pollutants and areas of concern on a national scale. This method could be valuable for countries with limited resources and infrastructures and could be used in combination with modelling and satellite based remote sensing to assess priorities. The ability to obtain in situ data of a large number of variables over vast areas in a short time may offsets the caveats associated with mobile measurements and a limited sample volume. / LG2017

Airborne DOAS measurements over the South African highveld

Broccardo, Stephen Paul January 2015 (has links)
A thesis submitted to the Faculty of Geography, Archaeology, and Environmental Studies University of the Witwatersrand, Johannesburg, in fulfilment of the requirements of the degree of Doctor of Philosophy. 2015. / An imaging DOAS instrument, along with in situ trace-gas and aerosol instrumentation was deployed on board a research aircraft over the Highveld region of South Africa, to make regional-scale measurements of nitrogen dioxide (NO2). The presence of a “hotspot” of NO2 over the Highveld is confirmed. Case-study estimates of NO2 emission flux were made downwind of a power station (10 tons.hr−1), a petrochemical plant (36 tons.hr−1) and the entire Highveld region (395 tons.hr−1). Vertical profile measurements were used to develop scenarios for a radiative transfer sensitivity study. From this, suitable air-mass factors for the DOAS measurements were determined. Comparisons between the airborne DOAS and satellite instruments show a good agreement where the spatial scales of the satellite ground pixels and the features in the two-dimensional trace-gas distribution are matched. A long-term record of satellite data was analysed. Analysis of radiative transfer revealed a possible artefact in the adjacent positive and negative trends evident on the Highveld. A correction to the satellite record for a seasonal bias was made, and found to be important over biomass burning regions in Angola and Zambia. Spatial features in a seasonal model of the satellite record are shown to correspond with known urban, industrial and biomass burning sources in the region. Signatures of soil emissions are also detected.

Characteristics of airborne particulate matter at the Boulder Atmospheric Observatory

Unknown Date (has links)
"Elemental concentrations of airborne particulate matter at the Boulder Atmospheric Observatory have been analyzed as a function of height, time, particle size, anthropogenic activity, surface conditions, and various meteorological parameters. Aerosols were sampled at heights up to 49 meters during a one week period when the ground was at least partially covered with snow and the bottom 100 meters of the atmosphere was very stable"--Abstract. / Typescript. / "April, 1982." / "Submitted to the Department of Meteorology in partial fulfillment of the requirements for the degree of Master of Science." / Advisor: William H. Mach, Professor Directing Thesis. / Includes bibliographical references (leaves 117-121).

The effect of particle size on the regional deposition of inhaled aerosols in an avian respiratory tract

Hayter, Richard Browning January 2010 (has links)
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