Due to economic, accessibility and security constraints, the majority of developing countries within the low-latitudes lack the capacity to establish networks of ground-based air pollution monitoring stations. As a result, there is a lack of systematic and consistent measurements and monitoring of the concentrations of air pollutants in most of these countries. In addition, there is the lack of verifiable inventories of sources of atmospheric emissions. In order to mitigate these constraints, this research presents an investigation into the relevance of currently available satellite sensors to estimate concentrations of air pollutants (carbon monoxide, nitrogen dioxide and tropospheric ozone) and carbon dioxide over the Niger Delta, a developing region in southern part of Nigeria. It further presents a methodological framework designed to interpolate column concentrations from satellite sensors over the entire study area using ordinary kriging interpolation techniques in ArcGIS Geostatistical Analyst. The study also carries out an assessment of the reliability and resolution of the interpolated surfaces based on a subjective categorisation of the number of column measurements available from satellites sensors and the mean of the Euclidean distances between the column measurements. The results indicate varying degrees of reliability and resolution depending on the climatic seasons in the Niger Delta. The results further show that measurements from satellite sensors are reliable means of measuring and monitoring total and tropospheric column concentrations of air pollutants over the Niger Delta. However, ground-based measurements are required to infer ground-level concentration of pollutants from satellite sensor measurements. Seasonal variations observed in the concentrations of air pollutants indicate higher concentrations during the dry season than during the wet season. In addition to the satellite sensor-based assessment of concentrations of air pollutants and CO2, this research designed and constructed a GIS-based Niger Delta Emission Inventory (NDEI) infrastructure for criteria air pollutants (carbon monoxide, particulate matter, nitrogen oxides and sulphur dioxide), methane, non-methane volatile organic compounds and carbon dioxide. The NDEI has point-source, line-source and area-source components. The construction of the inventory infrastructure effectively relied on the interoperability of GIS and spreadsheet. Due to the lack of access to data, the infrastructure is populated with data generated based on a series of assumptions. This produced estimates with varying degree of uncertainties. Despite these uncertainties, the methods applied in generating data are transferrable to other developing regions where there is limited access to data required for estimating emissions. In addition, the process successfully validates the functionality of the infrastructure to produce accurate emission estimates as and when data that are more accurate are available. Although the estimates of emissions generated from the inventory have limited accuracy, the spatial distributions of the emissions have varying degree of accuracy. The most reliable estimates and spatial distribution of estimates are generated from the area-source (residential) component of the inventory due to the available data and the assumptions applied. The spatial distribution of emissions generated from the inventory are accurate to the extent of the available input spatial data. The thesis concludes by recommending further research work to explore opportunities to infer ground level concentrations of pollutants from satellite sensor measurements. In addition, the thesis recommends the implementation of a site survey to collect site-specific information in order to refine the input data into the NDEI to produce accurate estimates of emissions. The recommendations made from this study aim towards enhancing the development of relatively inexpensive means of measuring and assessing air quality for developing regions within the low latitudes.

No description available.

Twenty one magnetotelluric and 16 magnetovariation soundings were taken on or near the Carnmenellis granite over periods in the range of 0.0078 seconds to 3000 seconds. The measured impedance tensors were analysed in detail using decomposition methods. All the data are distorted by galvanic electric charges which build up on the granite country rock contact. The amount of distortion varies between sites with distance from the edge of the batholith. The vast majority of the data are at least two dimensional and the effects of three dimensional induction are increasingly sensed by periods greater than 1s. Short period soundings indicate that the anisotropy in the magnetotelluric field is caused by electric current being channelled along fluid filled cracks. One dimensional modelling of the E-pol response indicates that the bottom of the granite is not flat, but slopes downwards to the south. This finding is evidence to support the theory that the Cornubrian granites originated SSE of their present position and were rafted NNW as a thin sheet. Two dimensional modelling suggests that at least a portion of the gradient of this slope is caused by the neglection of 3D induction in models used in the study. The pattern of regional azimuths between 0.1 and 10 seconds is caused by a combination of lateral, near surface, conductivity contrast, such as the surrounding seas, and conductivity contrasts at depth due to the slope of the bottom of the granite. Mainly due to the effects of conductivity contrasts perpendicular to the regional azimuth, it was found impossible to find a model which fitted the E-pol data at both on and off granite sites. The 2D model indicates that there is a steep rise in the resistivity depth profile of the granite from 800 ohm-m at the surface to 20000 ohm-m at 4 km. The closure of fluid filled joints due to the increase in lithological load with depth is interpreted to be the cause of this increase in resistivity.

No description available.

No description available.

In this thesis the idea of using neural networks as a forward model for the EOS-MLS (Earth Observation System – Microwave Limb Sounder) is considered for a direct assimilation scheme. Neural networks are a type of non-linear regression technique that can provide fast, accurate results and are used extensively in many different fields. Here a neural network is constructed to act as a forward model for the EOS-MLS. The neural network uses a temperature profile and tangent pressure levels as inputs and produces the corresponding radiance profile for one channel of the EOS-MLS. The work here primarily concentrates on one band of the EOS-MLS that is centred on an oxygen line and whose radiances are affected only by temperature for the majority of the channels. It shows that a neural network can function as a forward model in this case, producing radiances that are within instrument noise and for most channels, within half the instrument noise. Adding ozone to the forward model affects the radiances in only two channels of this band, increasing the radiances in some minor frames by around ~10K. It was found that this difference could be accounted for in the neural network forward model by adding ozone to the inputs. A second band, which is centred on an ozone line, is briefly considered. It was found that above 150hPa the radiances from this band could be modelled well using a neural network. Below this height, the neural network produced large errors in radiance (of around 1.5K – four times the instrument noise). This is thought to be due to the effects of water vapour. A problem specific to limb sounders that must be faced when doing direct assimilation is determining the tangent pressures of the radiances. During retrieval, these tangent pressures are normally retrieved as part of the state vector and discarded. For an assimilation process, these tangent pressures may be unavailable and have to be deduced in some way. Here, a neural network is used to retrieve tangent pressures outside the assimilation process. These retrieved tangent pressures can then be used by the forward model and assumed to be correct. It was found that tangent pressures could be retrieved with an accuracy of around 50m, much better than required for a forward model. The final problem faced within this thesis is the creation of the Jacobian of the instrument forward model. This is the derivative of the radiances with respect to the state vector and is used by the assimilation process to update the model fields during the assimilation process.

In 1990, four 50m-long sediment cores were recovered from Lac du Bouchet, a small maar crater lake in the Massif Central of France. The sediment was deposited continuously over the last 300,000 years (3 full glacial-interglacial cycles), and forms a high resolution sequence which is the subject of multi-disciplinary examination at laboratories in Edinburgh, Marseille and Louvain. This thesis is concerned with the use of palaeomagnetic measurements to reconstruct the past geomagnetic field, and the use of rock-magnetic measurements to complement the other disciplines in reconstructing past environmental conditions at Lac du Bouchet. The study is an extension of previous studies of 20m-long cores from Lac du Bouchet, which covered the last 120,000 years. The cores were sampled at 2&h183;5cm spacing, giving a total of around 2500 samples. The natural remanent magnetisation (NRM), and laboratory implanted magnetisations (susceptibility, IRM and ARM) of each sample were measured. The top 20m of the sequence had already been dated by <SUP>14</SUP>C to 45 ka, and by correlation to the marine δ<SUP>18</SUP>O stratigraphy back to δ<SUP>18</SUP>O stage 5e. The organic-rich sediments between 32 and 37m depth have been correlated to δ<SUP>18</SUP>O stage 7 by palynology, and the base of the core is thought to be of δ<SUP>18</SUP>O stage 9 age. The magnetic measurements of susceptibility, IRM and ARM principally reflect the concentration of the magnetic mineral (a low-Ti titano-magnetite) which is derived from the maar crater walls. Susceptibility is low in organic sediments deposited in warm climates, and the record has a very close inverse correlation to the arboreal/non-arboreal pollen ratio. It therefore provides a record of the palaeoenvironment at Lac du Bouchet. The δ<SUP>18</SUP>O sub-stages 5a-e and 7a-e are well defined; substantial changes in susceptibility occur within the last two interglacials; and short duration susceptibility flows punctuate the last glacial.

The geology of the High Pieria Mountains and the southern edge of the Vermion Mountains in the North Thessaly area of Greece is described in detail. The area stretches from the Veria-KoFani road in the north to the Mavroneri Valley in the south, and from the foot of the eastern slopes of the Pieria to the western slops above the Aliakmon River. An informal stratigraphic scheme is established for the area. Detailed petrological descriptions of the stratigraphic units are given, from which it is shown that they were all metamorphosed in a single episode to the garnet grade of the greenschist facies. It is deduced that the temperature and pressure of the metamorphism lay in the ranges 400 to 450 °C and 6.0 to 6.76kb. Detailed descriptions of the major and minor structures of the units are given, showing that the rocks have been subjected to four deformation episodes, in addition to late high-angle faulting. The first episode was contemporaneous with the metamorphism. The second episode is interpreted as being part of the same orogenic event as the first. The structural work shows that the Pieria Mountains are a stack of thrust sheets (the Pieria allochthon) emplaced in their present position along the basal lavroneri Thrust in post-L. Cretaceous times (probable Eocene). The stack itself was however built up at the time of the first deformation episode. Rb-Sr isotopic evidence shows that this first deformation episode occurred in the Valanginian stage of the L. Cretaceous. In addition the original crystallisation of the Pieria Granodiorite is shown by U-Pb isotopic analysis of zircons to have occurred in the Westphalian stage of the U. Carboniferous. Finally, the current state of knowledge of the pelagonian zone rocks and of the adjacent zones is reviewed, and a tectonic model proposed into which the findings of the study can be fitted.

No description available.

The feasibility of the magnetic variation field for electromagnetic investigations in the audiomagnetotelluric frequency range is tested at two separate locations in southeastern Scotland in the vicinity of the Southern Upland Fault complex (Lammermuir Fault). The Lammermuir Fault represents a lateral conductivity contrast in that it separates conductive Carboniferous sediments from resistive Ordovician meta-sediments. For one of the experiments and for the first time, a new generation of instruments (S.P.A.M. Mk. III) could be used for data acquisition. The instrument is operated as a network of geophysical sensors, it uses digital data communication between sites and provides on-line data quality control of all connected channels. For the experiment, we installed a 15-channel configuration of three synchronous AMT sites. All recorded data were re-processed off-line, with a newly developed S.P.A.M. Mk.III-compatible data processing package. The software is based on robust statistics and an integrated database helps to organise all relevant information. Despite some problems with noise, the overall quality of the data is satisfying. Both locations reveal strong vertical magnetic field anomalies. The anomalies are resolved convincingly in frequency and space. Contrary to our original assumptions, the observed anomalies at neither location can be modelled using two-dimensional techniques. However, three-dimensional thin sheet models show that strong current channelling into a surface conductor can explain very large induction arrows. Full three-dimensional modelling of the data is necessary to fit both, real and imaginary parts of the observed induction arrows. The modelling results indicate that a SE/NW striking conductive feature at the surface is duplicated at greater depth and dips towards the south. S.P.A.M. Mk.III is ideally suited to collect data of densely spaced sites for such electromagnetic mapping experiments or possibly three-dimensional data sets in future projects. Vertical magnetic field anomalies can be detected over the whole AMT frequency range and they are more robust against noise than the electric fields. A further development of the geomagnetic variation mapping method at high frequencies is therefore highly recommended.