This thesis studies the scattering properties of different types of imperfections in large Arctic and Antarctic ice sheets. Such irregularities include cracks, pressure ridges and both open and refrozen leads. The scattering by a transition region between sea ice and a very thick ice shelf, for example as is found in the Ross Sea in Antarctica, is also treated. Methods of solution are based on applications of Green�s theorem to the appropriate situation, which leads to either a single integral equation or a pair of coupled integral equations to be solved at the boundary between the ice and the sea water. Those equations over a finite interval are solved using numerical quadrature, while those over semi-infinite ranges are solved using the Wiener-Hopf method. Results calculated using different techniques are able to be checked against each other, giving us great confidence in their accuracy. In particular, the scattering by three ice sheets of different thicknesses is confirmed analytically by mode-matching coupled with the residue calculus technique. The scattering by the single irregularities is investigated partly for its own sake, and partly with the aim of using it to treat the scattering when large numbers of features are included in a single ice sheet. The principal objective of doing this is to observe the change in the general amounts of reflection and transmission as the background ice thickness is changed. There is enough variation in our results for us to conclude that there is definite potential for using the change in an incident wave spectrum after passing through a given ice field to estimate the background ice thickness.

Thesis (PhD)--University of South Australia, 1998

88 leaves : ill., maps, tables, photos. (part col.) ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Thesis (Ph.D.1976) from the Dept. of Botany, University of Adelaide

220 leaves : ill., maps, photos ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Thesis (Ph.D.1976) from the Dept. of Botany, University of Adelaide

308 p. : ill. ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Thesis (Ph.D.)--Dept. of Botany, University of Adelaide, 1976

Thesis (PhD)--University of South Australia, 1998

308 p. : ill. ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Thesis (Ph.D.)--Dept. of Botany, University of Adelaide, 1976

Levels of carbon dioxide in the atmosphere have been steadily increasing since the beginning of the Industrial Revolution in the 1800s. The earth's climate is sensitive to alterations in these levels of carbon dioxide and other greenhouse gases (GHG), with significant changes in climate predicted long term. The adoption of the Kyoto Protocol in 1997 heralded a new age in terms of greenhouse gas accounting and emissions responsibility, for all nations. In Australia, carbon emissions from the Land Use and Land Use Change and Forestry sector are responsible for a large proportion of the national total emissions. Radar remote sensing has demonstrated considerable potential in the estimation and mapping of vegetation biomass and subsequently carbon. The aim of this research is to investigate the potential of airborne polarimetric radar for quantifying and mapping the biomass and structural diversity of woodlands in semi-arid Australia. Initial investigation focussed on the physical structure of the woodland, which revealed that despite a diversity of woodland associations, the species diversity was relatively low. Both excurrent and decurrent growth forms were present, which subsequently resulted in varying allocation of biomass to the components (i.e., branches, trunks). In view of this, both empirical and modelling methodologies were explored. Empirical relationships were established between SAR backscatter and the total above ground biomass. Considerable scatter was present in these relationships, which was attributed to the large range of species and their associated structures. Comparison of actual and model simulations for C-, L- and P-band wavelengths, reveal that no significant difference existed for these wavelengths, except at CHH, and the cross-polarised data at L- and P-band. The study confirmed that microwaves at C-band interacted largely with the leaves and small branches, with scattering at VV polarization dominating. Compared to the lower frequencies, the return from the ground surface (as expected) was significant. The differences in scattering mechanisms (i.e., branch-ground versus trunk-ground) between excurrent and decurrent structures were due largely to the larger angular branches associated with Eucalyptus and Angophora species, which were absent from Callitris glaucophylla.

Thesis (M.S. - Renewable Natural Resources)--University of Arizona. / Includes bibliographical references.

Thesis (Ph. D. - Arid Land Studies)--University of Arizona, 1983. / Includes bibliographical references (leaves 147-152).