In 2011, the Canadian enhanced Polar Outflow Probe (ePOP) satellite will be launched. The ePOP satellite is equipped with several scientific Earth observation instruments, including a Radio Receiver Instrument (RRI) which will be used to detect High Frequency (HF) radio waves transmitted from a ground-based transmitter. The ground-based instrument will be one of the Super Dual Auroral Radar Network (SuperDARN) array of radars. A radio wave transmitted from the SuperDARN radar will propagate through the ionosphere and be detected by the RRI on ePOP. Analysis of the characteristics of the signal received by the RRI will provide information about the plasma density in the ionosphere between the transmitter and receiver. As the ePOP satellite is not yet operational, extensive ray path modelling has been performed to simulate the expected signal at the RRI for various ionospheric conditions.<p> The other major objective of this research was to examine the effect of the variable refractive index in the ionosphere on SuperDARN drift velocity measurements. Past comparisons between velocities measured by SuperDARN and other instruments have found that velocities measured by SuperDARN typically were about 20-30% lower. This research has shown that underestimation of drift velocities by SuperDARN is a consequence of not including the refractive index when these velocities are calculated. As refractive index measurements are not readily available, this research has involved developing and implementing various methods to estimate the refractive index in the ionosphere. These methods have demonstrated that plasma density values within the SuperDARN scattering volume are appreciably higher than background plasma densities in the ionosphere. Application of these methods, which has resulted in a much better understanding of the physics of the coherent scattering process, has resulted in agreement between velocities measured by SuperDARN and other instruments.

The growing need for better definition of flow units and depositional heterogeneities in petroleum reservoirs and aquifers has stimulated a renewed interest in outcrop studies as reservoir analogues in the last two decades. Despite this surge in interest, outcrop studies remain largely two-dimensional; a major limitation to direct application of outcrop knowledge to the three dimensional heterogeneous world of subsurface reservoirs. Behind-outcrop Ground Penetrating Radar (GPR) imaging provides high-resolution geophysical data, which when combined with two dimensional architectural outcrop observation, becomes a powerful interpretation tool. Due to the high resolution, non-destructive and non-invasive nature of the GPR signal, as well as its reflection-amplitude sensitivity to shaly lithologies, three-dimensional outcrop studies combining two dimensional architectural element data and behind-outcrop GPR imaging hold significant promise with the potential to revolutionize outcrop studies the way seismic imaging changed basin analysis. Earlier attempts at GPR imaging on ancient clastic deposits were fraught with difficulties resulting from inappropriate field techniques and subsequent poorly-informed data processing steps. This project documents advances in GPR field methodology, recommends appropriate data collection and processing procedures and validates the value of integrating outcrop-based architectural-element mapping with GPR imaging to obtain three dimensional architectural data from outcrops. Case studies from a variety of clastic deposits: Whirlpool Formation (Niagara Escarpment), Navajo Sandstone (Moab, Utah), Dunvegan Formation (Pink Mountain, British Columbia), Chinle Formation (Southern Utah) and St. Mary River Formation (Alberta) demonstrate the usefulness of this approach for better interpretation of outcrop scale ancient depositional processes and ultimately as a tool for refining existing facies models, as well as a predictive tool for subsurface reservoir modelling. While this approach is quite promising for detailed three-dimensional outcrop studies, it is not an all-purpose panacea; thick overburden, poor antenna-ground coupling in rough terrains typical of outcrops, low penetration and rapid signal attenuation in mudstone and diagenetic clay- rich deposits often limit the prospects of this novel technique.

L'information obtenue par le radar polarimétrique est utilisée en recherche depuis une trentaine d'années. Ce qui fait du radar polarimétrique un outil unique pour sonder l'atmosphère, c'est sa capacité de fournir de l'information à distance sur les propriétés des hydrométéores. Il est donc permis d'espérer pour l'avenir une meilleure compréhension des processus microphysiques en présence dans les précipitations. Plusieurs méthodes ont été développées jusqu'à maintenant pour se rapprocher de ce but. Poursuivant les efforts d'études précédentes sur les précipitations stratiformes et convectives, nous avons essayé d'obtenir une forme de présentation des données polarimétriques qui interprète les processus dominants dans les précipitations en examinant la variabilité des observables polarimétriques. Le défi de cette étude a été d'identifier les processus microphysiques dans les précipitations stratiformes en suivant l'évolution de la croissance des hydrométéores à travers la variabilité des observables polarimétriques. Nous avons obtenu les profils moyens des variables polarimétriques pour des cas stratiformes survenus de novembre 2003 à avril 2005. Nous avons construit les diagrammes de la distribution des variables polarimétriques représentant leur variabilité dans l'espace réflectivité (Z) - hauteur (H) d'après une méthodologie élaborée dans ce but. Nous avons testé nos hypothèses et validé nos résultats pour quatre cas sélectionnés. La nouvelle forme de présentation des données que nous avons élaborée en nous servant des variables polarimétriques fournit un outil supplémentaire pour identifier les processus microphysiques dominants dans les précipitations stratiformes. La méthodologie a été adaptée pour tenir compte des particularités des précipitations stratiformes et, combinée avec l'information extraite par d'autres instruments et d'autres méthodes, peut servir à compléter l'image globale d'événements de précipitation. ______________________________________________________________________________ MOTS-CLÉS DE L’AUTEUR : Le radar polarimétrique, Les variables polarimétriques, L'identification des hydrométéores.

Los radares de apertura sintética basados en tierra (GB-SAR) son instrumentos que, aun siendo relativamente jóvenes, se utilizan con éxito para monitorizar operacionalmente deslizamientos de tierra. Por otra parte, el manto nivoso se ha estudiado tradicionalmente a nivel local con sensores invasivos o con radares de onda continua. El trabajo presentado en esta tesis contribuye a la conjunción de ambos campos: el uso de sensores GB-SAR para la monitorización del manto nivoso. En los capítulos 5, 6 y 7 se muestran las tres técnicas desarrolladas: cálculo de la altura del manto nivoso, cálculo del volumen de nieve desplazado en una avalancha, y detección y clasificación de avalanchas.La altura del manto nivoso se calcula a partir de la fase interferométrica diferencial de dos adquisiciones SAR consecutivas bajo la hipótesis de nieve seca y asumiendo un modelo de nieve de una capa. El volumen desplazado en una avalancha se obtiene mediante la resta de dos modelos del terreno digitales (DTM) generados justo antes y después del fenómeno avalancha. Los DTMs se obtienen con el modo topográfico del instrumento: dos antenas separadas una cierta distancia reciben simultáneamente los ecos de una tercera antena que transmite. La tercera técnica de monitorización, detección y clasificación de avalanchas, se realiza mediante la magnitud de la coherencia compleja entre dos imágenes SAR consecutivas. Las avalanchas de nieve presentan valores de coherencia muy bajos en el área afectada, que puede ser identificada mediante un modelo basado en características morfológicas y estadísticas. En la presente tesis se presenta un innovador algoritmo para la detección y clasificación de avalanchas.El GB-SAR del Joint Research Centre, una vez mejorado para permitir su uso continuado 24h al día y 7 días a la semana (capítulo 3), ha sido utilizado para desarrollar y verificar las técnicas mencionadas anteriormente. Se han realizado medidas durante seis inviernos, que han proporcionado más de 120000 imágenes SAR a una frecuencia aproximada de 12 minutos por imagen. Se han estudiado dos emplazamientos, cada uno con características diferentes con el fin de verificar el uso operativo de las técnicas bajo condiciones reales. Los resultados muestran que la obtención de la altura del manto nivoso es posible pero su aplicación está limitada al campo experimental ya que su uso está condicionado por fuertes restricciones. Un estudio de viabilidad posteriormente confirmado con medidas muestra, en cambio, las limitaciones de precisión de los instrumentos GB-SAR para obtener una estima del volumen de nieve desplazado en una avalancha. Finalmente, la técnica más prometedora es la de detección y clasificación de avalanchas, la cuál se demuestra factible y robusta desde un punto de vista operativo y práctica desde una perspectiva de usuario final. / Ground-based synthetic aperture radars (GB-SAR) are instruments that, although relatively young, are operationally used to monitor landslides with sub-millimetre accuracy. There are however other application fields that deserve some attention. Monitoring of the snow cover and, in particular, of those processes associated with the snow avalanches are a clear example of this. To date, monitoring of the snow cover has been traditionally carried out at local scale either with invasive sensors or with continuous wave (CW) radars, while at wider scales air- or satellite-borne sensors have been employed. The work presented in this PhD thesis is a first attempt to study the potential use of GB-SAR sensors to monitor the snow cover. Three techniques for monitoring snow cover with GB-SAR are presented through Chapters 5, 6 and 7: snow height retrieval, snow avalanche volume retrieval and avalanche events detection and classification.Snow height is retrieved by using the differential interferometric phase of two consecutive SAR acquisitions under the assumption of single layer model and dry snow conditions. The volume displaced in a snow avalanche is computed by subtracting two digital terrain models (DTM) generated immediately before and after the avalanche event.DTMs are obtained with the topographic interferometric mode of the instrument: a spatial base line separates two antennas that simultaneously receive the echoes of a third transmitting antenna. The third monitoring technique, avalanche detection and classification, is achieved identifying low-coherence anomalies in the coherence image between two successive SAR acquisitions. Snow avalanches present a low-coherence signature that can be identified by a morphological and statistical parameter model. A novel detection and classification scheme for snow avalanches is proposed.The Joint Research Centre's GB-SAR sensor, upgraded to allow continuou operation 24 hours a day 7 days a week, also as part of the work of this thesis (Chapter 3), was used to develop and assess the before mentioned techniques. Measurements were carried out during six winters, providing more than 120000 SAR images at a rate of one image every 12 minutes approximately. Two test sites were studied, each with different characteristics in order to assess under real conditions the operational use of the monitoring techniques. Results show that snow height retrieval is achievable but remains, for the moment, an on-going research topic due to strong constraints limiting its use. A feasibility study is presented showing the accuracy limitations of GB-SAR to compute the snow volume involved in an avalanche. Finally, the most promising technique is snow avalanche detection and classification, which is demonstrated to be feasible and robust from an operational point of view and practical from an end user perspective.

This report presents concepts for a planar active electronically scanned antenna(AESA). The goal of the project was to devlop a low-weight, low profile, thin, S-band antenna with wide-scan angle capabilities. In the final concept the service aspects of the T/R-modules was also taken into acount in order to allow easy and fast replacements of these components. The antenna was designed and optimised using the commercial software Ansoft HFSS. A prototype of the antenna was constructed and later measured and verified. The final concept is a 2m×2m antenna with an estimated weight of around 320 kg, around 11 cm thick (where the thickness of the antenna element is 1.76 cm) and has a maximum scan angle range of more than 45 degrees (with &lt;–10dB active reflection) in the frequency band 3–3.5 GHz.

In 2011, the Canadian enhanced Polar Outflow Probe (ePOP) satellite will be launched. The ePOP satellite is equipped with several scientific Earth observation instruments, including a Radio Receiver Instrument (RRI) which will be used to detect High Frequency (HF) radio waves transmitted from a ground-based transmitter. The ground-based instrument will be one of the Super Dual Auroral Radar Network (SuperDARN) array of radars. A radio wave transmitted from the SuperDARN radar will propagate through the ionosphere and be detected by the RRI on ePOP. Analysis of the characteristics of the signal received by the RRI will provide information about the plasma density in the ionosphere between the transmitter and receiver. As the ePOP satellite is not yet operational, extensive ray path modelling has been performed to simulate the expected signal at the RRI for various ionospheric conditions.<p> The other major objective of this research was to examine the effect of the variable refractive index in the ionosphere on SuperDARN drift velocity measurements. Past comparisons between velocities measured by SuperDARN and other instruments have found that velocities measured by SuperDARN typically were about 20-30% lower. This research has shown that underestimation of drift velocities by SuperDARN is a consequence of not including the refractive index when these velocities are calculated. As refractive index measurements are not readily available, this research has involved developing and implementing various methods to estimate the refractive index in the ionosphere. These methods have demonstrated that plasma density values within the SuperDARN scattering volume are appreciably higher than background plasma densities in the ionosphere. Application of these methods, which has resulted in a much better understanding of the physics of the coherent scattering process, has resulted in agreement between velocities measured by SuperDARN and other instruments.

Data from the National Oceanic and Atmospheric Administration wind profiling radar network for the period 2002 2005 were used to investigate the effects of precipitation, topography and gravity waves on the measurements of winds by wind profilers, and to study the climatology and sources of atmospheric gravity waves. The comparison of the profiler winds to the NCAR/NCEP reanalysis and MM5 model winds revealed that monthly averaged wind profiler vertical velocities are strongly affected by precipitation in the lowest 3 km of the troposphere, both directly by hydrometeor velocity and indirectly via gravity wave activity produced by convection. We have determined that presence of downward wind velocities with magnitudes larger than 0.25 m/s is the sign of precipitation-affected data. This velocity threshold was used for identifying and correcting the contaminated data. The characteristics of the gravity waves in three period bands (6 min - 1 hour, 1 - 3 hours and 3 - 12 hours) and three orthogonal spatial components were obtained using spectral analysis of the profiler winds. The most kinetic energy was found to be associated with the low-frequency horizontal component of gravity waves. A consistent seasonal pattern and geographical distribution of kinetic gravity wave energy were observed in the troposphere, with maxima reaching ~25 J/kg in winter at 8 - 10 km altitude. A technique for quantifying the topography variance near the measurement sites was developed and applied to evaluate the effects of topography on gravity wave generation. We have determined that topography is an important source of the medium- and high-frequency waves in the middle troposphere. Correlation and regression analyses were used to study sources of the gravity waves. Convection was found to explain a significant part of the vertical component of the kinetic gravity wave energy throughout the troposphere and total kinetic energy in the lower troposphere, while vertical shear of the zonal wind was the predominant source in the upper troposphere. The results of this study are important for interpreting the wind measurements by wind profiling radars and for improving gravity wave parameterizations in global circulation models.

Ten years (1997 - 2006) of summer (June, July, August) daytime (14 - 00 Z) Weather Surveillance Radar - 1988 Doppler data for Houston, TX were examined to determine the best radar-derived lightning forecasting predictors. Convective cells were tracked using a modified version of the Storm Cell Identification and Tracking (SCIT) algorithm and then correlated to cloud-to-ground lightning data from the National Lightning Detection Network (NLDN). Combinations of three radar reflectivity values (30, 35, and 40 dBZ) at four isothermal levels (-10, -15, -20, and updraft -10 degrees C) and a new radar-derived product, vertically integrated ice (VII), were used to optimize a radar-based lightning forecast algorithm. Forecasts were also delineated by range and the number of times a cell was identified and tracked by the modified SCIT algorithm. This study objectively analyzed 65,399 unique cells, and 1,028,510 to find the best lightning forecast criteria. Results show that using 30 dBZ at the -20 degrees C isotherm on cells within 75 km of the radar that have been tracked for at least 2 consecutive scan produces the best forecasts with a critical success index (CSI) of 0.71. The best VII predictor was 0.734 kg m-2 on cells within 75 km of the radar that have been tracked for at least 2 consecutive scans producing a CSI of 0.68. Results of this study further suggest that combining the radar reflectivity and VII methods can result in a more accurate lightning forecast than either method alone.

Two new stepped-frequency continuous wave (SFCW) radar sensor prototypes, based on a coherent super-heterodyne scheme, have been developed using Microwave Integrated Circuits (MICs) and Monolithic Millimeter-Wave Integrated Circuits (MMICs) for various surface and subsurface applications, such as profiling the surface and subsurface of pavements, detecting and localizing small buried Anti-Personnel (AP) mines and measuring the liquid level in a tank. These sensors meet the critical requirements for subsurface and surface measurements including small size, light weight, good accuracy, fine resolution and deep penetration. In addition, two novel wideband microstrip quasi-TEM horn antennae that are capable of integration with a seamless connection have also been designed. Finally, a simple signal processing algorithm, aimed to acquire the in-phase (I) and quadrature (Q) components and to compensate for the I/Q errors, was developed using LabView. The first of the two prototype sensors, named as the microwave SFCW radar sensor operating from 0.6-5.6-GHz, is primarily utilized for assessing the subsurface of pavements. The measured thicknesses of the asphalt and base layers of a pavement sample were very much in agreement with the actual data with less than &#61590;0.1-inch error. The measured results on the actual roads showed that the sensor accurately detects the 5-inch asphalt layer of the pavement with a minimal error of &#61590;0.25 inches. This sensor represents the first SFCW radar sensor operating from 0.6-5.6-GHz. The other sensor, named as the millimeter-wave SFCW radar sensor, operates in the 29.72-35.7-GHz range. Measurements were performed to verify its feasibility as a surface and sub-surface sensor. The measurement results showed that the sensor has a lateral resolution of 1 inch and a good accuracy in the vertical direction with less than &#61590; 0.04-inch error. The sensor successfully detected and located AP mines of small sizes buried under the surface of sand with less than 0.75 and 0.08 inches of error in the lateral and vertical directions, respectively. In addition, it also verified that the vertical resolution is not greater than 0.75 inches. This sensor is claimed as the first Ka-band millimeter-wave SFCW radar sensor ever developed for surface and subsurface sensing applications.

Connectivity is considered one of the fundamental aspects that influences the rate of mass movement in the landscape. The connectivity aspect has been acknowledged from various conceptual geomorphic frameworks. None of these provided a developmental methodology for studying the connectivity of geomorphic systems, especially at the scale of the fluvial system. The emphasis in this research is placed on defining variables of the geomorphic systems that influence the connectivity potential of these systems. The landscape gradient, which is extracted from the Digital Elevation Model (DEM), and the surface roughness, which is extracted from radar images, are used to analyze the connectivity potential of geomorphic systems in the landscape. Integration of these variables produces a connectivity potential index of the various geomorphic systems that compose the fluvial system. High values of the connectivity potential index indicate high potential of the geomorphic system to transport mass whereas the low values indicate low potential of the geomorphic system to transport mass in the landscape. Using the mean values of the connectivity potential index, the geomorphic systems in the landscape can be classified into geomorphic systems of low connectivity potential, geomorphic systems of intermediate connectivity potential and geomorphic systems of high connectivity potential. In addition to the determination of the relative connectivity potential of various geomorphic systems, the connectivity potential index is used to analyze the system-wide connectivity. The ratios between the connectivity potential index of the upstream geomorphic systems and the connectivity potential index of the downstream geomorphic systems define system-wide connectivity in the landscape. High ratios reflect the high potential of the upstream geomorphic systems to transport mass in the downstream direction. Low ratios indicate the influence of the downstream geomorphic systems in maximizing mass movement in the upstream geomorphic systems. The presence of high and low ratios suggests the presence of a high system-wide connectivity. As the ratio approaches unity, mass movement is minimized in the landscape indicating low system-wide connectivity. Applying the above approach to Estufa Canyon, Texas, illustrated that Estufa Canyon is a dynamic fluvial system with high system-wide connectivity.