L'atmosphère moyenne de la Terre est un laboratoire naturel pour les études de la dynamique géophysique des fluides et de l'optique pour la mesure des gaz. Les recherches dans cette région ont longtemps été limitées par le manque d'observations à long terme susceptibles de couvrir l'ensemble de la région, de la troposphère à la haute mésosphère et à la thermosphère inférieure. Les dernières décennies ont vu la construction de nombreux observatoires au sol et le lancement d'instruments par satellite dans le but de fournir les mesures nécessaires pour comprendre la chimie, la dynamique et les changements climatiques à long terme de l'atmosphère moyenne. La télédétection atmosphérique, tant au sol que dans l’espace, présente des avantages et des inconvénients évidents. Les premiers étant capables de fournir des mesures bien calibrées et à haute résolution sur un seul site et les derniers permettant une couverture globale au prix de la résolution et d'un certain degré de certitude lors de l'étalonnage. Pour ce travail, nous utilisons des mesures de température obtenues à l'aide d'une technique de télédétection au sol basée sur le lidar à diffusion de Rayleigh et nous effectuons des comparaisons systématiques avec les profils de température générés à l'aide de trois instruments de télédétection passif basés sur des satellites: Sondeur Micro-onde sur satellite Aura (MLS). Sondage de l'atmosphère par radiométrie des émissions à large bande (SABER) et surveillance mondiale de l'ozone par occultation d'étoiles (GOMOS).Ce manuscrit a trois résultats principaux: 1a) Résultats de plusieurs améliorations de l’algorithme de la température lidar, qui ont permis de corriger un bias froid sur les températures mésosphériques jusqu’à 20 K à 90 km. 1b) Meilleur accord entre les températures du lidar et les profils de température SABER et MLS entre 70 km et 90 km. 1c) Une validation croisée entre les températures d’un lidar de température de Rayleigh et d’un lidar d’ozone co-localisés, qui donne confiance en la stabilité de la technique du lidar et justifie l’utilisation de la température par lidar comme base de données de référence pour la validation par satellite. 2a) Présentation d’une comparaison décennale entre les températures lidar validées et les températures produites par SABER et MLS. 2b) Nous montrons un biais froid dans les mesures satellitaires par rapport au lidar (-6 K pour SABER et -17 K pour MLS) dans la région de stratopause, un biais chaud (6 K près de 60 km) dans la mésosphère d’été, et un biais structuré verticalement pour MLS (-4 à 4 K) qui couvre la moyenne atmosphère. 2c) Nous réduisons l'ampleur du biais en dècallant verticalement la hauteur de la stratopause satellite et constatons une amélioration de la comparaison de température lidar-satellite qui en résulte. Ce résultat a des implications importantes pour la notification des températures des satellites en fonction de la hauteur géopotentielle. 3a) La comparaison des profils de température lidar avec la nouvelle base de données de température GOMOS montre que les altitudes géométriques des satellites peuvent être mieux estimées par les techniques d'occultaion que par l'inférence des niveaux de pression à partir des données radiométriques 3b) de l'effet des marées sur les comparaisons de température entre lidar et satellite lorsque Le passage supérieur du satellite est décalé dans le temps par rapport à la mesure lidar et peut être de l'ordre de 2 à 4 K en fonction de la phase de l'heure solaire. / The Earth's middle atmosphere is a pristine natural laboratory for the study of geophysical fluid dynamics and optics in neutral gasses. Research in this region has long been limited by a lack of long-term observations which are capable of covering the entire region from the troposphere to the upper mesosphere and lower thermosphere. Past decades have seen the construction of many ground based observatories and launches of satellite based instruments in an effort to provide the measurements needed to understand the chemistry, dynamics, and long-term climactic changes in the middle atmosphere. Both ground-based and space-based atmospheric remote sensing have clear strengths as well as limitations; the former being able to provide high resolution, well calibrated measurements at a single site and the latter allowing for global coverage at the cost of resolution and some degree of certainty in calibration. For this work we are using temperature measurements produced from a Rayleigh-scatter lidar ground-based remote sensing technique and making systematic comparisons to temperature profiles produced from three passive scanning satellite-based remote sensing instruments: Microwave Limb Sounder on the Aura satellite (MLS), Sounding of the Atmosphere using Broadband Emission Radiometry (SABER), and Global Ozone Monitoring by Occultation of Stars (GOMOS).This manuscript has three main results: 1a) Results of several improvements to the lidar temperature algorithm resulting in a cooling of the mesospheric temperatures by up to 20 K at 90 km. 1b) Better agreement between the cooled lidar temperatures and temperature profiles from SABER and MLS between 70 km and 90 km. 1c) A cross-validation between temperatures from a co-located Rayleigh temperature lidar and ozone lidar which provides confidence in the stability of the lidar technique and justification for the use of lidar temperatures as a reference database for satellite validation. 2a) Presentation of a decadal comparison between the validated lidar temperatures and the temperatures produced by SABER and MLS. 2b) We show a cold bias in the satellite measurements with respect to the lidar (-6 K for SABER and -17 K for MLS) in the stratopause region, a warm bias (6 K near 60 km) in the summer mesosphere, and a vertically structured bias for MLS (-4 to 4 K) which spans the middle atmosphere. 2c) We reduce the magnitude of the bias by vertically shifting the height of the satellite stratopause and see an improvement in the resulting lidar-satellite temperature comparison. This result has important implications for the reporting of satellite temperatures as a function of geopotential height. 3a) Comparison of lidar temperature profiles with the newly created GOMOS temperature data base shows that satellite geometric altitudes can be better estimated by occultaion techniques than by inference of pressure levels from radiometric data 3b) The effect of tides on lidar to satellite temperature comparisons when the satellite overpass is temporally offset from the lidar measurement can be on the order of 2 to 4 K depending on the phase of the solar hour.

Un algorithme permettant d’estimer précisément les paramètres des tourbillons de sillage (positions et circulations) en utilisant les données spectrales fournies par un LIDAR a été développé. Il s’articule en 3 grandes étapes : La première permet de détecter la présence de tourbillon et d’en faire une localisation grossière grâce à la méthode des enveloppes de vitesses. La seconde étape a pour but d’affiner l’estimation des positions des tourbillons en utilisant une optimisation du critère des moindres carrés. Cette étape permet également de faire une première estimation de la circulation des tourbillons. La troisième et dernière étape se concentre sur l’estimation des circulations des tourbillons en maximisant le critère de vraisemblance. Les estimations sont de plus en plus fines et se concentrent au fur et à mesure sur les paramètres les plus critiques. La mise au point de cet algorithme a nécessité d’utiliser plusieurs modèles (LIDAR, tourbillons de sillage, atmosphère) et de formuler un certain nombre d’hypothèses et approximations simplificatrices afin d’atteindre un coût calculatoire raisonnable. L’algorithme proposé a ensuite fait l’objet d’une évaluation de performances, l’intérêt étant porté sur la robustesse par rapport aux différents bruits altérant la mesure, en particulier celui lié à la turbulence atmosphérique et par rapport aux erreurs de modèle. Cette évaluation a été menée à la fois sur des données simulées à l’aide de modèles paramétriques simplifiés, et sur des données de simulations aux grandes échelles.Les paramètres instrumentaux du LIDAR constituent de potentiels degrés de liberté pour améliorer les performances de l’estimateur, en particulier pour les grandeurs les plus critiques, c’est-à-dire les valeurs de circulation. Le calcul des performances de l’estimateur nécessitant un coût de calcul non négligeable, il se prête mal à des fins d’optimisation. C’est pourquoi une étude de l’influence des paramètres du LIDAR sur la Borne de Cramér-Rao (BCR) a été menée. Cette étude a permis de mieux comprendre l’influence des paramètres instrumentaux et d’aboutir à une configuration optimale pour la BCR. / An algorithm was developed to estimate precisely wake vortices parameters (positions and circulations) using spectral data provided by a LIDAR. It is articulated in 3 main stages: The first one allows to detect the presence of vortices and to make a rough localization thanks to the method of the velocity envelopes. The second step is to refine the estimation of vortex positions using an optimization of the least squares criterion. This step also permits to make an first estimation of the vortices circulation. The third and final step focuses on estimating vortex circulations by maximizing the likelihood criterion. Estimates are becoming finer and more focused on the most critical parameters. The development of this algorithm required the use of several models (LIDAR, wake vortices, atmosphere) and to formulate a number of simplifying assumptions in order to reach a reasonable computational cost. The proposed algorithm was then subjected to a performance evaluation, the interest being focused on the robustness with respect to the different noises altering the measurement, particularly the one related to the atmospheric turbulence, and with respect to the model errors. This evaluation was carried out both on simulated data using simplified parametric models, and on Large Eddy Simulations.The instrumental parameters of LIDAR are potential degrees of freedom to improve the performance of the estimator, in particular for the most critical quantities, that is to say the circulation values. The calculation of the performance of the estimator requiring a significant computational cost, it lends itself poorly for optimization purposes. This is why a study of the influence of the LIDAR parameters on the Cramér-Rao Bound (CRB) was carried out. This study allowed to understand the influence of the instrumental parameters and to reach an optimal configuration for the CRB.

In this thesis, I demonstrate a single­photon Light Detection And Ranging, (LiDAR)system operating at 1550 nm capable of reconstructing 3D environments live withmm resolution at a rate of 400 points per second using eye­safe laser pulses. Thesystem was built using off­-the-­shelf optical components and analysis was performedusing open-­source software. I utilise a single superconducting nanowire single photondetector (SNSPD) with 19 ps time jitter and 85% detection efficiency to achieve a 4 psdepth resolution in live measurements. I also show that by performing slightly moretime costly post analysis of the data it is possible to increase the details and smoothnessof the images. Furthermore, I show that the same LiDAR system and much of the algorithms usedfor 3D LiDAR can be used to perform Optical Time Domain reflectrometry (OTDR)measurements. I demonstrate that the system can identify interfaces between differentrefractive mediums such as fibre to fibre or fibre to air couplings with a depth resolutionof 9 mm along a single line. Using these reflections, I also show that the systemcan identify flaws in optical fibres as well as measure certain characteristics suchas absorption coefficient due to Rayleigh scattering or thermal expansion. Lastly, Idemonstrate that the same OTDR principles used in fibres can be applied to free­s-paceoptical setups and that the system can identify specific optical elements as well asmeasure the quality of the alignment of an optical system. / I detta projekt demonstrerar jag ett enstaka foton Light Detection And Ranging,(LiDAR) system som använder ljus med 1550 nm våglängd som är ofarliga för ögon.Systemet kan återskapa 3D miljöer i realtid med 400 punkter per sekund med mmprecision. Systemet är byggt med kommersiellt tillgängliga komponenter och all dataanalys utfördes med open­source mjukvaran ETA. Jag använder en superconductingnanowire single photon detector, (SNSPD) med 19 ps timing jitter och 85 % effektivitetför att uppnå en precision på 4 ps i mätningarna. Jag visar också att genom utföramer tidskrävande post­analys av datan så är det möjligt att öka upplösningen ochjämnheten i bilderna. Utöver detta visar jag att samma LiDAR system och algoritmer kan användas för attutföra Optical Time Domain reflectrometry, (OTDR) mätningar. Jag visar att systemetkan urskilja olika reflektioner från fiber till fiber och fiber till luft kopplingar. Med hjälpav dessa reflektioner visar jag också att det är möjligt att identifiera brister i optiskafiber samt mäta olika egenskaper av fibern som absorbtions koeffcient eller termiskkontraktion. Slutligen visar jag att samma principer av OTDR som används i fiber kantillämpas till free­-space optiska system och att det är möjligt att identifera olika optiskaelement samt bedömma linjeringen av det optiska systemet.

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Where once the Arctic basin held predominantly old, thick perennial sea ice, it is now increasingly occupied by young, thin seasonal ice. The sea ice surface topography, which affects and is affected by many of the physical processes operating at the interface between ocean, sea ice and atmosphere, is closely related to the age and type of sea ice cover. In this thesis, new methods are presented for measuring and understanding sea ice topography using Light Detection and Ranging (LiDAR) technology. A new technique is presented for parameterizing the micro-scale roughness of sea ice using terrestrial LiDAR. Field, laboratory and numerical experiments have been carried out to test the precision and accuracy of the technique, and calibrations have been developed for correcting field observations of surface roughness for known biases. Results obtained using this technique have been applied in several microwave remote sensing and electromagnetic-wave scattering model studies of snow-covered and melting sea ice. Terrestrial and satellite LiDAR observations are acquired and combined in a further study to examine how sea ice surface topography regulates the melting of ice during the Arctic summer. Observations from a field program in the Canadian Arctic show that minor variations in the roughness of pre-melt sea ice topography can affect significant variations in the melt pond coverage at the ice surface in summer. Numerical simulations are used to develop a quantitative understanding of these findings and, when applied to satellite observations, explain most of the spatial variation in Arctic summer ice melting rates. Results suggest that a recent reduction in sea ice roughness, caused by progressive changes in the type of sea ice resident in the Arctic Ocean, has accelerated the summer melting and decline of the Arctic sea ice cover. / May 2016

More than 54% of the world population lives in urban areas, and this percentage is projected to increase rapidly in future years. This growth significantly affects the hydrological cycle, which translates into social and economic costs due to urban flooding. This thesis develops a procedure to evaluate the current storm water infrastructure using Airborne LiDAR data. This evaluation is essential to mitigate and prevent the effect of floods in urban areas. Airborne LiDAR data provides the elevation data necessary to characterize the elements involved in the storm water system. The processing of this data, digitization, and characterization of the storm drainage system is computed with ArcGIS, Geographic Information System (GIS) software. Scenarios for 4 return periods (2, 10, 25 and 100 years) are modeled using StormCAD in order to evaluate the capacity of the stormwater sewer system in the northwest area of The University of Texas at Austin main campus. The performance of the drainage system might work under strain for a 100-year storm event; therefore, it is suggested to modify the pipe sizes to prevent flooding in the area analyzed. The results indicate that the methodology proposed for evaluating the current conditions of a stormwater drainage system produces valid results, but can be improved using Ground-based LiDAR data. / text

Master of Arts / Department of Geography / Kevin P. Price / Due in large part to changes in land management practices, eastern redcedar (Juniperus virginiana L.), a native Kansas conifer, is rapidly invading onto valuable rangelands. The suppression of fire and increase of intensive grazing, combined with the rapid growth rate, high reproductive output, and dispersal ability of the species have allowed it to dramatically expand beyond its original range. Based on its abundance and invasive nature there is a growing interest in harvesting this species for use as a biofuel. For economic planning purposes, density and biomass quantities for the trees are needed. Three methods are explored for mapping eastern redcedar and quantifying its biomass in Riley County, Kansas. First a comparison of plot-regression versus individual tree based techniques is conducted to determine the optimal approach for characterizing redcedar tree canopy using LiDAR (Light Detection and Ranging). Second a hybrid approach is utilized to characterize redcedar canopy biomass using LiDAR and high-resolution multispectral imagery. Finally, to explore alternative methods of characterizing the three-dimensional structure of redcedar canopy a comparison of “Structure from Motion” photogrammetric techniques and LiDAR is conducted. These methods showed promising results and proved to be useful in the forestry, range management, and bioenergy industries for better understanding the potential of invasive redcedar as a biofuel resource.

Peatlands are unique and important landscape systems, providing valuable ecosystem services such as water and carbon storage, water supply and flood attenuation. They are known to account for more than 10% of the world’s terrestrial carbon store and represent 50 – 70% of the global wetland resource. The UK government’s decision to support the IUCN, UK Peatland Program Commission of Inquiry on Peatlands, recognises the importance and urgency with which action is needed to understand and restore damaged peatland landscapes, and their associated ecosystem services. To meet this need, it is recognised that peatlands in the South West of the UK are important as bio-climatically and functionally marginal peatlands that are undergoing extensive restoration to reinstate key ecological and hydrological function. This thesis aims to improve understanding of the temporal and spatial variability of the ecohydrological structure and function of peatland ecosystems in the South West UK, and will provide the first baseline for the spatially distributed extrapolation of change across larger landscape extents. The research seeks to characterise the structure and function of peatland ecohydrology across multiple spatial and temporal scales. This is accomplished by bringing together remote sensing analyses of ecohydrological structure and function coupled with an integrated and high resolution hydrological monitoring system to characterise the spatial and temporal variability of runoff production and water storage across two headwater catchments. Key outcomes of this research are: 1. The development of novel methods to assess the spatial distribution of near surface hydrology in upland ecosystems using airborne thermal imaging data, 2. Improved understanding of how laser altimetry data can be used to measure the ecohydrology of landscapes more appropriately. 3. An empirical understanding of both the spatial and temporal variability of hydrology across representative sites within the moorlands of the South West UK. The high-resolution monitoring data are the first to describe the hydrological processes operating in these peatlands systems effectively, and provide an insight into how these processes are controlled by the anthropogenic drainage networks that are present throughout this shallow marginal peatland system.

Este trabalho, sendo pioneiro no Brasil, teve o intuito de efetuar uma investigação das nuvens cirrus na região Metropolitana de São Paulo (23,33ºS / 46,44ºW), SP, através do sistema MSP-Lidar para o período de Junho à Julho de 2007. Durante este período, foi verificada uma ocorrência de cirrus de aproximadamente 54% sobre o total de medidas efetuadas pelo sistema Lidar. Medidas com Lidar nos forneceram uma alta resolução espacial e temporal destas nuvens, permitindo assim caracterizá-las e classificá-las de acordo com as suas propriedades macro- e microfísicas. Para obter tais parâmetros, uma metodologia própria foi desenvolvida na recuperação dos dados de Lidar e uma robusta estatística foi aplicada para determinar as diferentes classes de cirrus. A metodologia adotada se resumiu basicamente (a) na determinação de períodos estacionários (ou observações) durante a evolução temporal de detecção de cirrus, (b) determinação da base e topo através de um valor limiar para o cálculo das variáveis macrofísicas (altitudes, temperaturas, espessuras geométricas), (c) aplicação do método da transmitância para cada camada de nuvem e a determinação das variáveis microfísicas (profundidade óptica e razão de Lidar). Neste processo, a razão de Lidar é calculada iterativamente até que haja a convergência da mesma. Análises estatísticas de multivariáveis foram efetuadas para a determinação das classes de cirrus. Estas classes são baseadas na espessura geométrica, altitude média e sua respectiva temperatura, a altitude relativa (diferença entre a altura da tropopausa e topo da nuvem) e a profundidade óptica. O uso sucessivo da Análise de Componentes Principais (PCA), do Método de Cluster Hierárquico (MCH) e da Análise de Discriminantes (AD) permitiu a identificação de 4 classes. Vale ressaltar que tais métodos foram aplicados somente para os casos identificados como camadas únicas de nuvens, pois não se observou significativamente a ocorrência de nuvens com multicamadas. A origem de formação das classes de cirrus encontradas, embora apresentando propriedades macro- e microfísicas distintas, foi identificada basicamente como a mesma, isto é, provenientes da injeção de vapor dágua na atmosfera por meio de sistemas frontais e seu respectivo resfriamento para a formação dos cristais de gelo. O mesmo mecanismo de formação também é atribuído aos jatos subtropicais. Uma análise em relação ao perfil de temperatura e a comparação com a literatura mostrou que as cirrus classificadas apresentam possivelmente cristais em forma de placas e colunas hexagonais. As razões de lidar (RL) calculadas também estão de acordo com a literatura. / This pioneer work in Brazil, aimed at investigating cirrus clouds in the metropolitan region of São Paulo (23.33 ºS / 46.44 ºW), SP, observed by the MSP-Lidar system in June and July 2007. During this period, cirrus clouds were observed during approximately 54% of the time of all Lidar measurements available. The Lidar provided measurements with high spatial and temporal resolution measurements of these clouds that allowed characterizing and classifying them according to their macro-and microphysical properties. For such parameters, a unique methodology was developed for the Lidar data retrieval and a robust statistic was applied to determine the different classes of cirrus. The following steps were adopted to characterize the observations: (a) the determination of stationary periods (or observations) during the time evolution of cirrus detection, (b) determination of the base and top of clouds through a so called threshold value to derive the macrophysical variables (altitude, temperature, geometrical thickness), (c) the application of the transmittance method for each layer and the determination of cloud microphysical variables (optical depth and Lidar ratio). In this process, the Lidar ratio is calculated iteratively until a convergence of this value is achieved. Multivariate statistical analyses were performed to determine the classes of cirrus. These classes are based on geometric thickness, average altitude and the respective temperature, relative altitude (difference between tropopause height and cloud top) and optical depth. The successive use of Principal Component Analysis (PCA), Hierarchical Clustering Method (HCM) and Discriminant Analysis (DA) allowed the identification of four classes of cirrus. It is important to point out here that such methods were applied only to cases identified as single layers of clouds, due to the rare occurrence of multilayered clouds. The origin of formation for the four cirrus classes, though they have distinct macro-and microphysical properties, was found to be basically the same, i.e., from the injection of water vapor in the atmosphere provided by frontal systems, followed by the cooling process to form ice crystals. The same formation mechanism is also attributed to the subtropical jet. An analysis of the temperature profile and comparison with the literature showed that the cirrus crystals possibly have the form of hexagonal plates and columns. The Lidar Ratio (LR) was also found to be in accordance with the literature.