Thesis (Ph.D.)--University of Melbourne, Dept. of Linguistics and Applied Linguistics, 2004. / Title from PDF file as viewed 9/8/05. Includes bibliographical references (leaves [497]-508)

Thesis (Ph. D.)--University of Washington, 2000. / Vita. Includes bibliographical references (leaves 172-178).

A mixing budget for the Strait of Georgia was prepared summarizing mixing processes and effects upon the physical oceanography of the strait. A mixing budget was defined as an itemized estimate of mixing mechanisms and the total state of mixing in the strait. Mixing effects in the Strait of Georgia were estimated from hydrographic data and from monthly summaries of meteorological data for four months: February, May, August and November of 1968. Mixing was estimated qualitatively by depth-averaging temperature, salinity, density and oxygen concentrations for four representative layers, each 25 metres thick and by producing contour plots for each variable for the layers (two upper layers, an intermediate layer and a deep layer). Quantitative estimates of mixing were made by computing the potential energy density and the energy density needed for total mixing for the representative layers plus the potential energy density of total stratification (a fresh water layer over a layer with oceanic salinity). Changes in potential energy were due to mixing plus advection. Estimates of the energy available for mixing were made for the different mixing mechanisms acting upon the strait: wind mixing, buoyancy flux (convection) mixing, tidal mixing, mixing by internal waves and entrainment mixing. The Strait of Georgia has three different domains which are influenced by different mixing mechanisms: the southern passages, the upper layers of the northern strait and the deep waters. The southern passages (including the San Juan Archipelago and Haro and Rosario Straits) are the site of intensive tidal mixing which keeps the entire water column well mixed} convection and wind mixing are also important during the winter. The upper layers of the northern strait (north of Boundary Pas sage) are well mixed by the wind in the winter and by the wind and convection in the autumn. The uppermost brackish layer is highly stratified in the spring and summer from the effects of surface heating and fresh water runoff; intermediate layers are mixed by entrainment upwelling. The deep waters of the strait are influenced chiefly by advection processes: estuarine flow and seasonal intrusions of new water masses. In the winter, cold low-salinity water intrudes and displaces the warm water left from the previous summer while in the summer, warm saline water replaces the cold winter water. / Science, Faculty of / Earth, Ocean and Atmospheric Sciences, Department of / Graduate

No description available.

No description available.

No description available.

The oceanic lithosphere forms as a residue of partial melting of the mantle beneath the mid-ocean ridge axis. Subduction of this residual layer has a profound impact on the Earth’s thermal and geochemical cycles as the recycling of this layer facilitates heat loss from the Earth’s interior and induces geochemical heterogeneities in the mantle. The goal of this study is to understand the thermal and geochemical evolution of the oceanic lithospheric mantle from a petrological perspective. An empirical geobarometer is calibrated for ocean island xenoliths in order to understand the thermal structure of the oceanic lithospheric mantle. The results of 0.1 MPa experiments from this study and high-pressure experiments from previous studies are used in the calibration. The uncertainties on pressures derived using the above geobarometer are high and hence could not be tested against thermal models for the oceanic lithosphere. The geochemical evolution of the oceanic lithospheric mantle involves post-melting geochemical modifications such as metasomatism. The geochemical evolution of the uppermost oceanic lithospheric mantle is studied using harzburgites from Hess Deep ODP Site 895, which are depleted in moderately incompatible elements relative to the global suite of abyssal peridotites. A comparison between Yb-abundances in Hess Deep harzburgites iii iv and those of a model depleted MORB mantle (DMM) residue reveals that the harzburgites have undergone up to 25% melting, assuming 0.5% melt porosity. Higher light and middle rare earth elements in the Hess Deep harzburgites than the model DMM melting residue are interpreted as the result of plagioclase crystallisation from melts being extracted by diffuse porous flow through the upper mantle. The effect of plagioclase crystallisation does not affect the chemistry of residual mineral phases as evidenced from the depleted light rare earth element abundances in clinopyroxene relative to the bulk rock. Ocean island xenoliths are studied to understand when and where metasomatism occurs in the deeper portion of the oceanic lithosphere. The median values of measured and reconstructed bulk concentration of Al2O3 in most ocean island xenoliths is lower than in abyssal peridotites, which generally would be interpreted as indicating a higher extent of melting in the former. However, a comparison between Yb- abundances in ocean island xenoliths and abyssal peridotites with a model DMM melting residue suggests that the extents of melting in the suites of rocks are broadly similar. Although fewer in number than ocean island xenoliths, abyssal peridotites from several locations have low concentrations of moderately incompatible elements. Metasomatism is observed in both, ocean island xenoliths and abyssal peridotites in the form of higher bulk rock Ce and Nd concentration than the model DMM melting residue but the extent of metasomatism is higher in ocean island xenoliths. There is no correlation between the concentrations of bulk rock Ce, Nd, Sm and Eu of ocean island xenoliths and age of the oceanic lithosphere from which the xenoliths originate. It is interpreted that metasomatism in the lower oceanic lithospheric mantle occurs near the ridge axis above the wings of the melting column. / Graduate / 0996 / 0372

Thesis (doctoral)--Delft University of Technology, Delft, The Netherlands. / Description based on print version record. Includes bibliographical references (p. [135]-144).

The profusion of observational data made available by the Venus Express and previous space missions, increases our need to develop numerical tools to interpret the data and improve our understanding of the Venus meteorology. The main objective of this work is to develop an improved Venus general circulation model and to study the most likely mechanisms driving the atmosphere to the current observed circulation. Our new model is an extension of a simplified version and includes a new radiative transfer scheme and convection and an adapted boundary layer scheme and dynamical core that take into account the dependence of the heat capacity with temperature, at constant atmospheric pressure. The new radiative transfer formulation implemented is more suitable for Venus climate studies than previous works due to its easy adaptability to different atmospheric conditions. This flexibility of the model was very important in this work to explore the uncertainties on the lower atmospheric conditions such as the gas absorption and the possible presence of aerosols near the surface. The new general circulation model obtains, after long periods of integration, a super-rotation phenomenon in the cloud region quantitatively similar to the one observed. However, this phenomenon is sensitive to some radiative parameters such as the amount of the solar radiative energy absorbed by the surface and the amount of clouds. The super-rotation in the model is formed due to the combined influence of the zonal mean circulation, thermal tides and transient waves, and the main mechanisms involved are identified and studied. In this process the momentum transported by the semidiurnal tide excited in the upper clouds has a key contribution. These migrating waves transport prograde momentum mainly from the upper atmosphere to the cloud region. In this work we also explored the model parameters to gain a better understanding of the effect of topography, the diurnal cycle and convective momentum mixing. In general the results showed that: the topography seemed capable of sustaining stronger global super-rotation; without diurnal cycle the strong winds in the cloud region are not produced; the convective momentum mixing experiment did not lead to significant changes. A simple experiment done advecting the UV absorber in the atmosphere, qualitatively showed several atmospheric phenomena that are important for the distribution of clouds. Among them is the presence of a region of low permeability isolating the polar vortex. This last experiment also showed that when increasing the amount of UV absorption in the upper cloud region the winds get stronger. Following the interpretation of observational data using numerical models, we also used a simplified version of the general circulation model to assess the accuracy of zonal wind retrievals from measured temperatures using the cyclostrophic thermal wind equation in the Venus mesosphere. From this analysis we suggest a method which better estimates the lower boundary condition, and improves the consistency of the results at high latitudes when compared with cloud tracking measurements.

This thesis describes a new algorithm based on the optimal estimation approach for the retrieval of atmospheric aerosol and surface properties from the Advanced Along- Track Scanning Radiometer (AATSR). This algorithm is a further development on the Oxford-RAL Retrieval of Aerosol and Cloud (ORAC). The new algorithm is set up to use both visible and infrared channels of AATSR to retrieve aerosol optical depth (AOD), effective radius, white sky albedo at four wavelengths (550, 670, 870, and 1600 nm), surface temperature and aerosol layer height. This thesis can be divided into three main parts : 1) the development of the new ORAC algorithm, 2) comparisons of the retrieved AOD with the aerosol products from visible-channel ORAC retrieval: GlobAEROSOL, and with the measurements from AErosol RObotic NETwork (AERONET), and 3) validations of the retrieved sea surface temperature (SST) with the measurements from ship-based radiometers (Infrared Sea surface temperature Autonomous Radiometer, ISAR) and the measurements from drifting buoys. In this thesis aerosols are assigned to four classes, marine clean at two different relative humidities, spherical dust and non-spherical dust. The estimated retrieval error is 0.012 in AOD and 0.083 K in SST. Comparing with the GlobAEROSOL products, the new algorithm (denoted by ORAC) retrieves lower AOD (0.071 ± 0.012) (median ± RMS) and higher sea surface albedo globally (0.067 ± 0.006). The lower AOD, which also occurs in regional scales, is a promising result as previous studies showed GlobAEROSOL overestimated AOD especially over open ocean. The comparison with ground-based measurements (AERONET) shows a good agreement between ORAC AOD and AERONET AOD over ocean, the correlation is 0.820 at 550 nm and 0.807 at 870 nm, and the differences in AOD between the two datasets are 0.067 ± 0.214 for 550 nm and 0.064 ± 0.167 for 870 nm. In contrast weaker corrections, 0.312 at 550 nm and 0.275 at 870 nm, are found over land, and the median difference between the two datasets are nearly 0.2 for both 550 μm and 870 μm. For three collocation criteria, the ORAC retrieved SST shows very high correlations with ISAR measurements (better than 0.980). Comparing with ISAR, ORAC SST has positive biases (0.150 to 0.117 K) and relative significant root mean squares (RMS) (0.481 to 0.430 K). Comparing with the drifting buoy measurements, the bias in retrieved SST is −0.067 ± 0.366 K for all the matches and −0.003 ± 0.298 K for the matches under high wind speed conditions (≥ 6 ms−1). The error analysis indicates the uncertainties in temperature profile, water vapour profile, surface emissivity and forward model may affect the accuracy of retrieved SST. These validation results suggest that the new ORAC algorithm is a successful approach to aerosol and surface retrieval over ocean, which is able to add to the current knowledge by improving current estimates of aerosol and surface properties. Most validation results presented in this thesis are under conditions of low AOD, it can been seen that the retrieved SST is not severely biased. Further validation is required to estimate the performance of ORAC at different levels of aerosol loading.