Submitted by Emanuel Varela Cardoso (emanuel.varela@ufcg.edu.br) on 2018-08-15T18:40:26Z No. of bitstreams: 1 FRANCINEIDE AMORIM COSTA SANTOS – TESE (PPGMet) 2015.pdf: 2985386 bytes, checksum: 4a052c9481457a7144e18ddda86f0b6d (MD5) / Made available in DSpace on 2018-08-15T18:40:26Z (GMT). No. of bitstreams: 1 FRANCINEIDE AMORIM COSTA SANTOS – TESE (PPGMet) 2015.pdf: 2985386 bytes, checksum: 4a052c9481457a7144e18ddda86f0b6d (MD5) Previous issue date: 2015-08-28 / Capes / Estudos sobre trocas energéticas entre ecossistemase a atmosfera são de grande importância no entendimento do papel da vegetação sobre o microclima local, sendo ainda bastante escassos quando se trata da vegetação da Caatinga. O presente trabalho tem o objetivo de estudar as diferenças no comportamento de importantes variáveis como o albedo (α), saldo de radiação (Rn), evapotranspiração (ET) e fluxos de CO2 (NEE e GPP) em área de Caatinga em recuperação (CREC) e degradada (CDEG) no estado da Paraíba. Em campo, os fluxos foram medidos pelo método da covariância de vórtices turbulentos (Eddy Covariance) para posterior comparação com as mesmas variáveis obtidas a partirde dados provenientes do sensor MODIS (Moderate Resolution Imaging Spectroradiometer) a bordo do satélite Terra. As estimativas mostraram maiores valores de albedo para a CDEG, e maiores valores de Saldo de radiação, para a CREC, evidenciando que nessa área deve existir uma maior disponibilidade de energia para realização dos processos físicos. O coeficiente de determinação (R2) entre as estimativas e as observações de Rn diário foi de até 0,93. A ET estimada pela metodologia SEBAL apresentou maiores diferenças com relação aos valores observados, fato porém a ser considerado foi a ocorrência de chuvas próximas a quase todas as datas das imagens. O algoritmo MOD16A2, no entanto, apresentou valores de ET mais próximos das observações e maior concordância com o Índice de Vegetação por Diferença Normalizada (NDVI). A CREC, em geral, apresentou maiores valores de ET em comparação com a CDEG. As trocas líquidas do ecossistema (NEE) com a atmosfera mostraram-se mais evidentes para a CREC, com a CDEG apresentando um aumento perceptível na absorção de CO2apenas na época chuvosa. A produtividade primária bruta (GPP) estimada a partir do MOD17A2, mesmo subestimando bastante os dados medidos, consegue diferenciar as duas áreas em estudo para todas as épocas do ano, ao passo que a metodologia aplicada em escala local, associando dados MODIS e medidas de campo (GPP_ mod) aproximou-se mais das observações, porém a diferença entre as duas áreas em estudo tornou-se mais evidente no período com menor disponibilidade hídrica. Os valores de R2 entre GPP_torre e GPP_MOD17 foram, respectivamente de 0,74 e 0,66 para CREC e CDEG. Já ente GPP_torre e GPP_ mod os valores de R2 foram menores, quais sejam: 0,35 e 0,51 para a CREC e CDEG, respectivamente. / Studies on energy exchanges between ecosystems and the atmosphere are of great importance in understanding the role of vegetation on the local microclimate, still quite sparse when it comes to the vegetation of the Caatinga. This work aims to study the differences in the behavior of important variables as the albedo (α), net radiation (Rn), evapotranspiration (ET) and CO2 fluxes (NEE and GPP) in Caatinga area in recovery (CREC ) and degraded (CDEG) in the state of Paraíba. In the field, the flows were measured by the method of Eddy Covariance for later comparison with the same variables derived from data from the MODIS (Moderate Resolution Imaging Spectroradiometer) aboard the Terra satellite. The estimates showed higher albedo values for the CDEG, and higher net radiation values for the CREC, showing that in this area there should be a greater availability of energy for realization of physical processes. The coefficient of determination (R2) between the estimates and observations of daily Rn reached 0,93. The ET estimated by SEBAL methodology showed higher differences in relation to the observed values, but fact to be considered was the rainfall next to almost all dates of the images. The MOD16A2 algorithm, however, presented closer ETvalues of the observations and the agreement with the normalized difference vegetationindex (NDVI). The CREC, in general, showed higher ET values in comparison with the CDEG. The Net ecosystem exchange (NEE) with the atmosphere were more evident to CREC, withthe CDEG showing a noticeable increase in CO2 absorption only in the rainy season. The gross primary production (GPP) estimated from the MOD17A2 even quite underestimating the measureddata, can differentiate the two areas under study for all seasons, whereas the methodology applied at the local level, linking MODIS data and measures field (GPP_ mod) moved closer to the observations, but the difference between the two areas under study became more evident in the shorter water availability. The R2 values between GPP_torre and GPP_MOD17 were respectively 0,74 and 0,66 for CREC and CDEG. Already being GPP_torre and GPP_ mod R2 values were lower, as follows: 0,35 and 0,51 for the CREC and CDEG, respectively.

L'objectif de cette thèse est de tirer parti d'une illumination totalement ou partiellement contrôlée pour enrichir l'acquisition vidéo de contenus tel que la reconstruction de la forme et de l'apparence. Aujourd'hui de nombreux travaux ont tenté d'atteindre cet objectif. Certains utilisent une illumination contrôlée et séquentielle pour obtenir des reconstructions de haute qualité de la forme et de la réflectance. En revanche, ces méthodes requièrent des dispositifs coûteuses et/ou ne fonctionnent pas en temps réel. Dans cette thèse, nous visions un système d'acquisition à bas coût, rapide et mobile, qui se veut non-seulement le moins intrusif possible mais aussi simple d'utilisation. La première contribution présentée dans cette thèse est une application de la méthode bien connue, intitulée stéréo photométrie, à la vidéo. De plus, comme une fréquence de trame élevée est nécessaire à une telle application, nous proposons une méthode permettant l'utilisation d'une illumination séquentielle avec des caméras rapides de type "electronic rolling shutter". Malgré les résultats intéressants obtenus, la qualité des reconstructions de l'apparence et de la forme n'étaient pas à la hauteur de nos espérances. De plus, la stéréo photométrie est une méthode qui, de nature, n'est pas très adaptée aux applications visées dans cette thèse. Pour notre seconde contribution, nous proposons une méthode de reconstruction de la forme (géométrie) ainsi que de la réflectance diffuse à partir d'une image (d'une séquence) en utilisant un système de capture hybride composé d'un capteur de profondeur (Kinect), d'une caméra grand public et d'un flash. L'objectif est de montrer qu'en combinant une acquisition RGB-D (image couleur + profondeur) avec illumination séquentielle, on peut obtenir une reconstruction qualitative de la forme et de la réflectance d'une scène dans le cas où l'éclairage n'est pas connu. Un couple d'images est capturé : une image non flashée (image sous une illumination ambiante) et une image flashée. Une image dont l'illumination ne provient que du flash (image flash pure) peut être calculée en soustrayant l'image non flashée de l'image flashée. Nous proposons un nouvel algorithme temps réel, qui, basé sur un modèle local d'illumination de notre flash et de l'image flash pure, améliore l'information de forme fournie par le capteur de profondeur tout en retrouvant les informations de réflectance diffuse. Notre dernière contribution concerne la composition automatique d'éclairage. L'éclairage est un élément clé de la photographie. Les professionnels travaillent régulièrement avec des systèmes d'éclairage complexes afin de capturer directement des images esthétiques. Récemment, certains photographes ont tenté une nouvelle approche : plutôt que photographier une scène directement sous un éclairage complexe, ils capturent la scène sous plusieurs éclairages simples, permettant ainsi un post-traitement permettant combiner les différentes illuminations de la scène. Cette approche apporte une nouvelle dimensionnalité intéressante au post-traitement. Cependant la combinaison des images requiert des compétences en matière de photographie, et l'acquisition sous différentes conditions d'éclairage n'en est pas moins fastidieuse. Nous proposons une méthode totalement automatisée, qui, à partir d'un modèle 3D (forme et albedo) reconstruit à partir de capture d'une scène réelle, produit virtuellement les images correspondant aux différentes conditions d'éclairages. Ensuite, ces images sont combinées automatiquement, à l'aide d'un algorithme génétique, pour correspondre à un style d'éclairage fourni par l'utilisateur sous forme d'une image cible de son choix. / The objective of this thesis is to take advantage of controlled illumination to enrich a video acquisition with shape and reflectance reconstructions. Today, a lot of works have tried to meet this objective. Some of them take advantage of sequential controlled illumintation to recover high quality shape and reflectance, however they either require a costly and very cumbersome fixed setup, and/or do not run in real-time. Our aim is a low cost, fast, mobile and simple acquisition setup which has to be the less intrusive possible so as to provide a greater ease of use. The first contribution of this thesis focuses on the application of the well known photometric stereo method to a video acquisition. Moreover, as a high frame rate is required by such an application, a method using sequential illumination with high frame rate cameras (electronic rolling shutter cameras) is also considered. Despite the interesting results provided by photometric stereo, we found that this latter did not provide enough qualitative results. Moreover, by its nature, photometric stereo is not really suitable for the range of applications targeted. We propose, as a second contribution, a method for recovering the shape (geometry) and the diffuse reflectance from an image (or video) using a hybrid setup consisting of a depth sensor (Kinect), a consumer camera and a partially controlled illumination (using a flash). The objective is to show how combining RGB-D acquisition with a sequential illumination is useful for shape and reflectance recovery. A pair of two images are captured : one non flashed (image under ambient illumination) and a flashed one. A pure flash image is computed by subtracting the non flashed image from the flashed image. We propose a novel and near real-time algorithm, based on a local illumination model of our flash and the pure flash image, to enhance geometry (from the noisy depth map) and recover reflectance information. Finally, our last contribution concerns an automatic method for light compositing, using rendered images. Lighting is a key element in photography. Professional photographers often work with complex lighting setups to directly capture an image close to the targeted one. Some photographers reversed this traditional workflow. Indeed, they capture the scene under several lighting conditions, then combine the captured images to get the expected one. Acquiring such a set of images is a tedious task and combining them requires some skill in photography. We propose a fully automatic method, that renders, based on a 3D reconstructed model (shape and albedo), a set of images corresponding to several lighting conditions. The resulting images are combined using a genetic optimization algorithm to match the desired lighting provided by the user as an image.

Modification of land use/land cover in South Florida has posed a major challenge in the region’s eco-hydrology by shifting the surface-atmosphere water and energy balance. Although drainage and development in South Florida took place extensively between the mid- and late- 20th century, converting half of the original Everglades into agricultural and urban areas, urban expansion still accounts for a dominant mode of surface cover change in South Florida. Changes in surface cover directly affect the radiative, thermophysical and aerodynamic parameters which determine the absorption and partitioning of radiation into different components at the Earth surface. The alteration is responsible for changing the thermal structure of the surface and surface layer atmosphere, eventually modifying surface-induced convection. This dissertation is aimed at analyzing the extent and pattern of land cover change in South Florida and delineating the associated development of urban heat island (UHI), energy flux alteration, and convective rainfall modification using observed data, remotely sensed estimates, and modeled results. Urban land covers in South Florida are found to have increased by 10% from 1974 to 2011. Higher Landsat-derived land surface temperatures (LST) are observed in urban areas (LSTu-r =2.8°C) with satisfactory validation statistics for eastern stations (Nash-Sutcliffe coefficient =0.70 and R2 =0.79). Time series trends, significantly negative for diurnal temperature range (DTR= -1°C, p=0.005) and positive for lifting condensation level (LCL > 20m) reveal temporal and conspicuous urban-rural differences in nocturnal temperature (ΔTu-r = 4°C) shows spatial signatures of UHI. Spatially higher (urban: 3, forest: 0.14) and temporally increasing (urban: 1.67 to 3) Bowen’s ratios, and sensible heat fluxes exceeding net radiation in medium and high-intensity developed areas in 2010 reflect the effect of urbanization on surface energy balance. Radar reflectivity-derived surface-induced convective rainfall reveals significantly positive mean differences (thunderstorm cell density: 6/1000 km2and rain rate: 0.24 mm/hr/summer, p < 0.005) between urban and entire South Florida indicating convective enhancement by urban covers. The research fulfils its two-fold purposes: advancing the understanding of post-development hydrometeorology in South Florida and investigating the spatial and temporal impacts of land cover change on the microclimate of a subtropical city.

No description available.

Forests affect climate by absorbing CO₂ but also by altering albedo, latent heat flux, and sensible heat flux. In this study we used the Community Earth System Model to assess the biophysical effect of North American temperate forests on climate and how this effect changes with location, tree type, and forest management. We calculated the change in annual temperature and energy balance associated with afforestation with either needle leaf evergreen trees (NET) or broadleaf deciduous trees (BDT) and between forests with high and low leaf-area indices (LAI). Afforestation from crops to forests resulted in lower albedo and higher sensible heat flux but no consistent difference in latent heat flux. Forests were consistently warmer than crops at high latitudes and colder at lower latitudes. In North America, the temperature response from afforestation shifted from warming to cooling between 34° N and 40° N for ground temperature and between 21° N and 25° N for near surface air temperature. NET tended to have lower albedo, higher sensible heat flux and warmer temperatures than BDT. The effect of tree PFT was larger than the effect of afforestation in the south and in the mid-Atlantic. Increasing LAI, a proxy for increased management intensity, caused a cooling effect in both tree types, but NET responded more strongly and albedo decreased while albedo increased for BDT. Our results show that forests' location, tree type, and management intensity can have nearly equal biophysical effects on temperature. A forest will have maximum biophysical cooling effect if it is in the south, composed of broadleaf PFT, and is managed to maximize leaf area index. / Master of Science

Aerosols affect the global radiation budget which plays an important role in determining the state of the Earth's climate. The heterogeneous distribution of aerosols and the variety in their properties results in high uncertainty in the understanding of aerosols. Aerosols affect the radiation by scattering and absorption (direct effect) or by modifying the cloud properties which in turn affects the radiation (indirect effect). The current work focuses only on the direct radiative effect of aerosols. The change in the top-of-atmosphere (TOA) reflected flux due to the perturbation of aerosols and their properties is called direct aerosol radiative forcing (ARFTOA). Estimation of ARFTOA using aerosol properties is done by solving the radiative transfer equation using a radiative transfer model. However, before using the radiative transfer model, it has to be validated with observations for consistency. This is done to check if the model is able to replicate values close to actual observations. The current work uses the Santa Barbara DISORT Atmospheric Radiative Transfer (SBDART) model. The output radiative fluxes from SBDART are validated by comparing with the Clouds and the Earth's Radiant Energy System (CERES) satellite data. Under clear-skies SBDART agreed with observed fluxes at TOA well within the error limits of satellite observations. In the shortwave solar spectrum (0.25-4 µm) radiation is affected by change in various aerosol properties and also by water vapour and other gas molecules. To study the effect of each of these molecules separately on the aerosol forcing at TOA, SBDART is used. ARFTOA is found to depend on the aerosol loading (aerosol optical depth – AOD), aerosol type (SSA) and the angular distribution of scattered radiation (asymmetry parameter). The role of water vapour relative to the aerosol layer height was also investigated and for different aerosol types and aerosol layer heights, it was found that water vapour can induce a change of ~4 Wm-2 in TOA flux. The relative importance of aerosol scattering versus absorption is evaluated through a parameter called single scattering albedo (SSA) which can be estimated from satellites. SSA defined as the ratio of scattering efficiency to total extinction efficiency, depends on the aerosol composition and wavelength. Aerosols with SSA close to 1 (sea-salt, sulphates) scatter the radiation and cool the atmosphere. Aerosols with SSA < 0.9 (black carbon, dust) absorb radiation and warm the atmosphere. Over high reflective surfaces a small change in SSA can change forcing from negative (cooling) to positive (warming). This makes SSA one of the most important and uncertain aerosol parameters. Currently, the SSA retrievals from the Ozone Monitoring Instrument (OMI) are highly sensitive to sub-pixel cloud contamination and change in aerosol height. Using the sensitivity of OMI to aerosol absorption and the superior cloud masking technique and accurate AOD retrieval of Moderate Resolution Imaging Spectroradiometer (MODIS), an algorithm to retrieve SSA (OMI-MODIS) was developed. The algorithm was performed over global oceans (60S-60N) from 2008-2012. The difference in SSA estimated by OMI-MODIS and that of OMI depended on the aerosol type and aerosol layer height. Aerosol layer height plays an important role in the UV spectrum due to the dominance of Rayleigh scattering. This was verified using SBDART which otherwise would not have been possible using just satellite observations. Both the algorithms were validated with cruise measurements over Arabian Sea and Bay of Bengal. It was seen that when absorbing aerosols (low SSA values) were present closer to the surface, OMI overestimated the value of SSA. On the other hand OMI-MODIS algorithm, which made no assumption on the aerosol type or height, was better constrained than OMI and hence was closer to the cruise measurement The presence of clouds results in a more complex interaction between aerosols and radiation. Aerosols present above clouds are responsible to most of the direct radiative effect in cloudy regions. The ARFTOA depends not only on the aerosol properties but also on the relative position of aerosols with clouds. When absorbing aerosols are present above clouds, the ARFTOA is highly influenced by the albedo of the underlying surface. Recent studies, over regions influenced by biomass burning aerosol, have shown that it is possible to define a ‘critical cloud fraction’ (CCF) at which the aerosol direct radiative forcing switch from a cooling to a warming effect. Similar analysis was done over BoB (6.5-21.5N; 82.5-97.5E) for the years 2008-2011. Aerosol properties were taken from satellite observations. Satellites cannot provide for aerosols present at different heights and hence SBDART was used to calculate the forcing due to aerosols present only above clouds. Unlike previous studies which reported a single value of CCF, over BoB it was found that CCF varied from 0.28 to 0.13 from post-monsoon to winter as a result of shift from less absorbing to moderately absorbing aerosol. This implies that in winter, the absorbing aerosols present above clouds cause warming of the atmosphere even at low cloud fractions leading to lower CCF. The use of multiple satellites in improving the retrieval of SSA has been presented in this thesis. The effect of aerosols present above clouds on the radiative forcing at TOA is shown to be different between Bay of Bengal and Atlantic Ocean. This was due to the change in SSA of aerosols during different seasons. The effect of aerosol height, aerosol type and water vapour on the TOA flux estimation is also studied using a radiative transfer model.

Im Rahmen der vorliegenden Arbeit wurde eine neuartige Lidartechnik in ein leistungsstarkes Lidar-System implementiert. Mit Hilfe des realisierten Aufbaus wurden Aerosol-Wolken-Wechselwirkungen in Flüssigwasserwolken über Leipzig untersucht. Die angewandte Messmethode beruht auf der Detektion von Licht, das an Wolkentröpfchen mehrfach in Vorwärtsrichtung gestreut und an Stickstoffmolekülen inelastisch zurückgestreut wurde. Dabei werden zwei Gesichtsfelder unterschiedlicher Größe verwendet. Ein Vorwärtsiterations-Algorithmus nutzt die gewonnenen Informationen zur Ermittlung von Profilen wolkenmikrophysikalischer Eigenschaften. Es können der Extinktionskoeffizient, der effektive Tröpfchenradius, der Flüssigwassergehalt sowie die Tröpfchenanzahlkonzentration bestimmt werden. Weiterhin wird die exakte Erfassung der Wolkenunterkantenhöhe durchdie eingesetzte Messtechnik ermöglicht. Darüber hinaus ist die Bestimmung von Aerosoleigenschaften mit dem eingesetzten Lidargerät möglich. Die Qualität des realisierten Messaufbaus wurde geprüft und eine Fehleranalyse durchgeführt. Unter anderem wurde der aus einer Wolkenmessung bestimmte Flüssigwassergehalt mit einem Mikrowellen-Radiometer bestätigt. Anhand von Fallbeispielen konnte das Potential dieser Messtechnik demonstriert werden. Die Bedeutung von Profilinformationen von Wolkeneigenschaften für die Untersuchung von Aerosol-Wolken-Wechselwirkungen wurde gezeigt. Weiterhin wurde mit Hilfe eines Doppler-Windlidars der Einfluss der Vertikalwindgeschwindigkeit auf Wolkeneigenschaften und damit Aerosol-Wolken-Wechselwirkungen verdeutlicht. Neunundzwanzig Wolkenmessungen wurden für eine statistische Auswertung bezüglich Aerosol-Wolken-Wechselwirkungen genutzt. Dabei konnte erstmalig die Abhängigkeit von Aerosol-Wolken-Wechselwirkungen von der Wolkeneindringtiefe untersucht werden. Es wurde festgestellt, dass diese auf die untersten 70m von Wolken beschränkt sind. Weiterhin wurden deutlich stärkere Aerosol-Wolken-Wechselwirkungen in Wolkengebieten festgestellt, die von Aufwinden dominiert werden. Für der Quantifizierung der Stärke von Aerosol-Wolken-Wechselwirkungen wurden ACIN-Werte genutzt, welche den Zusammenhang zwischen der Tröpfchenanzahlkonzentration und dem Aerosol-Extinktionskoeffizienten beschreiben. Dabei wurde zwischen der Untersuchung der entsprechenden mikrophysikalischen Prozesse und deren Bedeutung für die Wolkenalbedo und damit dem Strahlungsantrieb der Wolken unterschieden. Für die erstgenannte Zielstellung wurde ein ACIN-Wert von 0.80 +/- 0.40 ermittelt, für Letztere 0.13 +/- 0.07.