Ondas de Rossby longas são ondas de larga escala que se propagam para o oeste com escala espacial de algumas centenas a vários milhares de quilômetros e desempenham um papel crítico na regulação da circulação do oceano. Sua propagação promove deslocamentos verticais da termoclina, muitas vezes da ordem de dezenas de metros, e causa variações de altura da superfície do mar que podem ser observadas através de dados de satélites altimétricos. A hipótese deste estudo é que existe uma fração significativa da variabilidade da velocidade geostrófica na superfície, associada a sinais propagantes para oeste. Para testá-la avaliamos a variabilidade da velocidade geostrófica meridional na superfície induzida pela passagem dessas ondas. Filtros digitais são necessários para distinguir sinais propagantes dos não-propagantes e permitiu a seleção da componente propagante para oeste com período aproximado de 12 meses. Velocidade de fase cp, período P, comprimento de onda λ, amplitude quadrática média A e o percentual de variância explicada σ2 desta componente foram estimados nos locais onde identificamos ondas de Rossby longas do primeiro modo baroclínico. Selecionamos perfis Argo posicionados em diferentes fases da mesma onda para averiguar a influência da sua propagação nos campos de temperatura, salinidade e densidade. Os resultados revelaram que a onda de Rossby anual de 237 mm de altura pode alterar o campo de densidade com valores de até 0,3 kg m-3 numa faixa de 240 m ao nível picnoclina. A variância explicada da componente meridional da velocidade geostrófica propagante para oeste em relação ao sinal original revelou que de 40% a 71% do sinal se propaga para oeste, corroborando a hipótese. / Long Rossby waves are large-scale waves which propagate westward with spatial scale ranging from a few hundred to several thousand kilometers. These waves play a critical role in the adjustment of ocean circulation. Their propagation cause vertical displacements of the thermocline, often of tens meters, and cause variations of sea surface height that can be observed on satellite altimeters data. The hypothesis of this study is that there is a significant fraction of surface geostrophic velocity variability associated with westward propagating signals. To test it, we assessed the variability of the meridional geostrophic velocity at the surface induced by the passage of these waves. Digital filters are necessary to distinguish the propagating from non-propagating signals and allowed for the selection of the westward propagating component with an approximate period of about 12 months. Phase speed cp, period P, wavelength λ, mean square amplitude A and percentage of explained variance σ2 of this component were estimated where long Rossby waves from the first baroclinic mode were identified. We selected Argo profiles data positioned at different phases of the same wave to verify the influence of its propagation on temperature, salinity and density fields. The results showed that the annual Rossby wave of 237 mm height can change the density field with values up to 0.3 kg m-3 about 240 m at pycnoclin level. The explained variance of the westward meridional component of geostrophic velocity relative to the original signal revealed that 40% to 71% of the signal propagates westward, supporting the hypothesis.

As ondas de Rossby são o mecanismo de ajuste às perturbações de grande escala dos fluidos geofísicos. Elas podem ser geradas localmente, forçadas pelo rotacional da tensão de cisalhamento do vento, ou remotamente, devido às perturbações na altura da picnoclina na borda leste. Medidas altimétricas da anomalia da altura do mar tem fornecido evidências robustas da existência destas ondas. Estudos recentes mostram que vórtices não lineares de mesoescala são responsáveis por uma grande parte da variabilidade dos registros altimétricos, tendo sido observados propagando juntamente com as ondas de Rossby. Os objetivos deste estudo são identificar (1) as regiões onde as ondas de Rossby longas lineares explicam as observações, (2) qual mecanismo de geração é dominante e (3) se as ondas propagam-se de forma contínua em condições de não linearidade. Um modelo linear de 1½ camada de ondas de Rossby forçado por dados de tensão de cisalhamento do vento de escaterômetros é utilizado para reproduzir as anomalia da altura do mar. As correlações entre os resultados do modelo linear e os dados altimétricos são de até 0,88. Os resultados sugerem que a dinâmica linear de ondas de Rossby longas explica uma parte significativa da variabilidade anual da anomalia da altura do mar nas regiões tropicais. A oscilação da picnoclina na borda leste é o principal mecanismo gerador de ondas de Rossby nos oceanos Atlântico e Índico, enquanto no Pacífico a fonte dominante das ondas é a forçante atmosférica local. Um modelo quase-geostrófico não linear é utilizado para analisar como as ondas de Rossby geradas na borda leste propagam-se e dissipam-se em condições idealizadas. Em latitudes mais baixas que 32°S, as ondas atravessam toda a bacia oceânica até adentrar a região de meandramento da corrente de borda oeste. Nesta região, a energia é espalhada em todas as bandas de frequência. As ondas de Rossby que estão na latitude crítica tem um papel intermediário na cascata de energia. Em latitudes mais altas que 32°S, as ondas de Rossby não cruzam a totalidade da bacia oceânica, tendo sua energia transferida para outros períodos em uma distância de pelo menos 1000 km da borda oeste. / Rossby waves are the large scale mechanism of adjustment to perturbations of geophysical fluids. They can be generated locally, due to forcing by wind stress curl, or remotely, due to perturbations in the pycnocline level at the eastern boundary. Altimetric measurements of sea level anomaly have been providing sturdy evidences of the existence of these waves. Recent studies argue that mesoscale eddies are responsible for a substantial amount of the variability of the altimeter records. Eddies have been shown to propagate along with Rossby waves. The purposes of this study are (1) to identify the regions where linear long Rossby waves explain the observations, (2) to determine which generation mechanism is dominant, and (3) to verify if these waves can continuously propagate in nonlinearity conditions. A linear 1½ layer model forced by scatterometer wind stress data has been used to reproduce the sea level anomaly. Correlations between the results of the linear model and the altimetric data are up to 0.88. Results suggest that the linear long Rossby wave dynamics explain a significant part of the sea level anomaly annual variability in the tropical oceans. The pycnocline fluctuations at the eastern boundary are the main mechanism of generation of Rossby waves in the Atlantic and Indian oceans. The local atmospheric forcing is the principal source of the waves in the Pacific Ocean. A quasi-geostrophic nonlinear model has been used to analyze how the Rossby waves generated at the eastern boundary propagate and dissipate in idealized conditions. In latitudes lower than 32°S, the waves cross all the ocean basin until entering the region where the western boundary current meanders. In this region, energy is scattered throughout the spectrum. The Rossby waves that are in their critical latitude have an intermediate role in the energy cascade. In latitudes higher than 32°S, the Rossby waves fail to completely cross the ocean basin. Their energy is transfered to other periods in a distance of at least 1000 km from the western boundary.

Ondas de Rossby longas são ondas de larga escala que se propagam para o oeste com escala espacial de algumas centenas a vários milhares de quilômetros e desempenham um papel crítico na regulação da circulação do oceano. Sua propagação promove deslocamentos verticais da termoclina, muitas vezes da ordem de dezenas de metros, e causa variações de altura da superfície do mar que podem ser observadas através de dados de satélites altimétricos. A hipótese deste estudo é que existe uma fração significativa da variabilidade da velocidade geostrófica na superfície, associada a sinais propagantes para oeste. Para testá-la avaliamos a variabilidade da velocidade geostrófica meridional na superfície induzida pela passagem dessas ondas. Filtros digitais são necessários para distinguir sinais propagantes dos não-propagantes e permitiu a seleção da componente propagante para oeste com período aproximado de 12 meses. Velocidade de fase cp, período P, comprimento de onda λ, amplitude quadrática média A e o percentual de variância explicada σ2 desta componente foram estimados nos locais onde identificamos ondas de Rossby longas do primeiro modo baroclínico. Selecionamos perfis Argo posicionados em diferentes fases da mesma onda para averiguar a influência da sua propagação nos campos de temperatura, salinidade e densidade. Os resultados revelaram que a onda de Rossby anual de 237 mm de altura pode alterar o campo de densidade com valores de até 0,3 kg m-3 numa faixa de 240 m ao nível picnoclina. A variância explicada da componente meridional da velocidade geostrófica propagante para oeste em relação ao sinal original revelou que de 40% a 71% do sinal se propaga para oeste, corroborando a hipótese. / Long Rossby waves are large-scale waves which propagate westward with spatial scale ranging from a few hundred to several thousand kilometers. These waves play a critical role in the adjustment of ocean circulation. Their propagation cause vertical displacements of the thermocline, often of tens meters, and cause variations of sea surface height that can be observed on satellite altimeters data. The hypothesis of this study is that there is a significant fraction of surface geostrophic velocity variability associated with westward propagating signals. To test it, we assessed the variability of the meridional geostrophic velocity at the surface induced by the passage of these waves. Digital filters are necessary to distinguish the propagating from non-propagating signals and allowed for the selection of the westward propagating component with an approximate period of about 12 months. Phase speed cp, period P, wavelength λ, mean square amplitude A and percentage of explained variance σ2 of this component were estimated where long Rossby waves from the first baroclinic mode were identified. We selected Argo profiles data positioned at different phases of the same wave to verify the influence of its propagation on temperature, salinity and density fields. The results showed that the annual Rossby wave of 237 mm height can change the density field with values up to 0.3 kg m-3 about 240 m at pycnoclin level. The explained variance of the westward meridional component of geostrophic velocity relative to the original signal revealed that 40% to 71% of the signal propagates westward, supporting the hypothesis.

As ondas de Rossby são o mecanismo de ajuste às perturbações de grande escala dos fluidos geofísicos. Elas podem ser geradas localmente, forçadas pelo rotacional da tensão de cisalhamento do vento, ou remotamente, devido às perturbações na altura da picnoclina na borda leste. Medidas altimétricas da anomalia da altura do mar tem fornecido evidências robustas da existência destas ondas. Estudos recentes mostram que vórtices não lineares de mesoescala são responsáveis por uma grande parte da variabilidade dos registros altimétricos, tendo sido observados propagando juntamente com as ondas de Rossby. Os objetivos deste estudo são identificar (1) as regiões onde as ondas de Rossby longas lineares explicam as observações, (2) qual mecanismo de geração é dominante e (3) se as ondas propagam-se de forma contínua em condições de não linearidade. Um modelo linear de 1½ camada de ondas de Rossby forçado por dados de tensão de cisalhamento do vento de escaterômetros é utilizado para reproduzir as anomalia da altura do mar. As correlações entre os resultados do modelo linear e os dados altimétricos são de até 0,88. Os resultados sugerem que a dinâmica linear de ondas de Rossby longas explica uma parte significativa da variabilidade anual da anomalia da altura do mar nas regiões tropicais. A oscilação da picnoclina na borda leste é o principal mecanismo gerador de ondas de Rossby nos oceanos Atlântico e Índico, enquanto no Pacífico a fonte dominante das ondas é a forçante atmosférica local. Um modelo quase-geostrófico não linear é utilizado para analisar como as ondas de Rossby geradas na borda leste propagam-se e dissipam-se em condições idealizadas. Em latitudes mais baixas que 32°S, as ondas atravessam toda a bacia oceânica até adentrar a região de meandramento da corrente de borda oeste. Nesta região, a energia é espalhada em todas as bandas de frequência. As ondas de Rossby que estão na latitude crítica tem um papel intermediário na cascata de energia. Em latitudes mais altas que 32°S, as ondas de Rossby não cruzam a totalidade da bacia oceânica, tendo sua energia transferida para outros períodos em uma distância de pelo menos 1000 km da borda oeste. / Rossby waves are the large scale mechanism of adjustment to perturbations of geophysical fluids. They can be generated locally, due to forcing by wind stress curl, or remotely, due to perturbations in the pycnocline level at the eastern boundary. Altimetric measurements of sea level anomaly have been providing sturdy evidences of the existence of these waves. Recent studies argue that mesoscale eddies are responsible for a substantial amount of the variability of the altimeter records. Eddies have been shown to propagate along with Rossby waves. The purposes of this study are (1) to identify the regions where linear long Rossby waves explain the observations, (2) to determine which generation mechanism is dominant, and (3) to verify if these waves can continuously propagate in nonlinearity conditions. A linear 1½ layer model forced by scatterometer wind stress data has been used to reproduce the sea level anomaly. Correlations between the results of the linear model and the altimetric data are up to 0.88. Results suggest that the linear long Rossby wave dynamics explain a significant part of the sea level anomaly annual variability in the tropical oceans. The pycnocline fluctuations at the eastern boundary are the main mechanism of generation of Rossby waves in the Atlantic and Indian oceans. The local atmospheric forcing is the principal source of the waves in the Pacific Ocean. A quasi-geostrophic nonlinear model has been used to analyze how the Rossby waves generated at the eastern boundary propagate and dissipate in idealized conditions. In latitudes lower than 32°S, the waves cross all the ocean basin until entering the region where the western boundary current meanders. In this region, energy is scattered throughout the spectrum. The Rossby waves that are in their critical latitude have an intermediate role in the energy cascade. In latitudes higher than 32°S, the Rossby waves fail to completely cross the ocean basin. Their energy is transfered to other periods in a distance of at least 1000 km from the western boundary.

<p>A common way to measure height in aerial vehicles is to use a radar height altimeter (RHM). Since the RHM transmits radar pulses that can be detected, a passive alternative would be desirable in military applications. The idea to use reflected signals from the Global Positioning System (GPS) as a bistatic radar, has been established over the last years. The GPS signals are already present and would not reveal aeroplanes in covert operations. </p><p>In this thesis, the use of reflected GPS signals as a bistatic, passive altimeter is examined. A simulation model has been developed and implemented, and simulations using the model have been done. Different types of ground cover have been investigated, both water and land types, with varying reflectivity and scattering behaviour. For larger terrain variations, e.g. mountains and valleys, a ground elevation database has been used. Furthermore, several parameters, like the antenna coverage and the satellite elevation angle, have been varied and the result of this examined. </p><p>The results of these simulations show that measuring height is possible for bothsea and land surfaces. The accuracy depends on several error factors, like a bias originating from surface roughness and measurement errors due to noise in the receiver. The simulations also show that the most important design parameter is the antenna, which must be designed to give a sufficiently large SNR, capture the specular reflection and avoid unwanted reflections.</p>

Frequency modulated continuous wave (FM-CW) radar altimeters are used in civil and military applications. Proximity fuses, automatic cruise control systems of cars, radar altimeter of planes are examples to these applications. The goal of this thesis is to present a method for altitude determination using an FM-CW radar. For this purpose principles of radars and FM-CW systems are studied and related subjects are inspected. After this inspection, algorithms for altitude determination are evaluated. Consequently signal detection and processing methods are proposed to build an altitude determining algorithm. Also an analytical test environment for altitudes between 100 m and 4000 m is developed in computer as a result of researches. Test environment simulated the performance of altitude determining algorithm and FM-CW Radar Altimeter. The hardware is designed and implemented accordingly.

Detta projekt har genomförts på företaget Haglöf Sweden AB i Långsele. Företaget har länge haft ett förslag till ett projekt som går ut på att mäta borrprover med hjälp av en android-enhet och även andra funktioner inom skogsindustrin. Den applikation som togs fram till företaget genom det här projektet blev en applikation som kan utföra enklare skogsinventeringar med hjälp av analyser av borrprover via kameran, höjdmätning med hjälp av accelerometer samt gps positioner från enheten. Dessa funktioner har sedan utvärderats mot traditionella verktyg inom skogsindustrin och fastställts att funktionerna är tillräckligt exakta för att kunna användas. / This project has been carried out for Haglöf Sweden AB in Långsele. The company has for many years had this project waiting because they lacked the resources to do it. The goal of the project is to create an application for android that can analyse tree core samples and other forestry functions. The resulting application has an altimeter, tree core reader/analyser and gps positioning. All these functions has later been evaluated against traditionally used equipment and is found to be good enough to use.

A common way to measure height in aerial vehicles is to use a radar height altimeter (RHM). Since the RHM transmits radar pulses that can be detected, a passive alternative would be desirable in military applications. The idea to use reflected signals from the Global Positioning System (GPS) as a bistatic radar, has been established over the last years. The GPS signals are already present and would not reveal aeroplanes in covert operations. In this thesis, the use of reflected GPS signals as a bistatic, passive altimeter is examined. A simulation model has been developed and implemented, and simulations using the model have been done. Different types of ground cover have been investigated, both water and land types, with varying reflectivity and scattering behaviour. For larger terrain variations, e.g. mountains and valleys, a ground elevation database has been used. Furthermore, several parameters, like the antenna coverage and the satellite elevation angle, have been varied and the result of this examined. The results of these simulations show that measuring height is possible for bothsea and land surfaces. The accuracy depends on several error factors, like a bias originating from surface roughness and measurement errors due to noise in the receiver. The simulations also show that the most important design parameter is the antenna, which must be designed to give a sufficiently large SNR, capture the specular reflection and avoid unwanted reflections.

Altimeter measures atmospheric air pressure and counts actual model altitude from it. Then sends data to ground module, which shows them on display. Ground module contains USB interface for connecting to PC. It enables upload of flight data and opportunity to show them in graphical representation.

The electromagnetic (EM) bias is the largest source of error in the TOPEX/Poseidon and Jason-1 satellite sea surface height (SSH) estimates. Due to incomplete understanding of the physical processes which cause the bias, current operational models are based on empirical relationships between the bias wind speed and significant wave height. These models reduce RMS estimation errors of the EM bias to approximately 4 cm. To improve EM bias estimation the correlation between the bias and RMS long wave slope is studies using data from tower-based experiments in the Gulf of Mexico and Bass Straight, Australia. Models based on significant wave height and RMS slope are more accurate than models based on wave height and wind speed by at least 50% in RMS error between predicted and ground truth bias values. Nonparametric models have been proposed as a method to reduce the variability of EM bias estimates. Using tower data, nonparametric models developed from wind speed and significant wave height measurements are shown to provide some improvement over parametric models. It is also shown that the historical discrepancy between satellite and tower EM bias measurements is reduced by nonparametric modeling. A validity study of rough surface scattering models is conducted for surfaces with Gaussian and power law power spectra. Models in the study include physical optics (PO), geometrical optics, small perturbation method, and small slope approximation. Due to the prevalence of the PO approximation, particular emphasis is placed on the development of a validity criterion for the PO model. An empirical study of the PO approximation shows that the validity of the model is more accurately described by the RMS wave slope than the classic surface curvature criterion for surfaces with a Gaussian power spectrum. For surfaces with a power law PSD, the accuracy of the PO approximation is related to the significant slope (RMS surface height/wavelength of the dominant spectral peak). The validity of other models in the study are also shown to be well approximated by bounds on surface slope. An EM bias model is derived using the physical optics scattering model, hydrodynamic modulation, and non-Gaussian long wave surface statistics. Using a modulation transfer function, the hydrodynamic modulation of small wave heights is shown to be linearly related to the long wave RMS slope. The resulting EM bias model expresses the relative bias as a function of the long wave surface parameters RMS wave slope, surface skewness, and tilt modulation. Coefficients of the long wave parameters are determined by the short ocean waves, and provide insight into the physical mechanisms that cause the bias. From measured values of the ocean surface profile, estimated values of the bias are computed from the bias model. A comparison of these estimated values with in situ EM bias measurements shows a strong correlation between the estimated and measured values. Nadir and off-nadir measurements of the EM bias collected during the BYU Off-Nadir Experiment (Y-ONE) are presented. The in situ measurements are compared with bias estimates computed from an off-nadir generalization of the nadir EM bias model. From theoretical and experimental bias measurements a model of the angular dependence of the bias is developed as a function of the normalized bias at nadir.