The objectives of this thesis are to assess: to what degree have natural resources deteriorated in a grazing area in northern Namibia, how do perceptions of environmental change held by local stakeholders there, correspond to scientific assessments, and how do these relate to national estimates? Analysis of the process of developing national indicators for monitoring of land degradation concluded that specific indicators should be developed on national level, and in some instances even on local level as there are no universal causes of land degradation. According to farmers overgrazing and low rainfall since the early 1990s cause negative environmental changes in the study area, partly confirming findings from national monitoring. Results also suggest that: less grazing outside the study area, improved access, permanent water supply, and fencing of large areas, also contributed. Results show that improved water supply was the most important factor. Investigation of the influence of permanent water points on grazing resources showed that perennial grasses are replaced by less palatable annual grasses as far as 6 km from water points along a water pipeline. No significant grazing induced changes in grass composition were observed around privately owned wells. Private ownership seems to be a key factor preventing over-utilization of grazing resources around the latter. A remote sensing study using Landsat TM imagery identified bare ground, saltpans and grassland with a fair accuracy. Separation of woodland from shrubland and shrubland from grassland was less accurate using supervised classification. The results show that the soil adjusted vegetation index provides valuable information about variations of green biomass over time in semi-arid environments. However, it is suggested that satellite based investigations should be supported by thorough ground based assessment due to the influence of underlying soil in this environment.

(English)Ozone is one of the most important greenhouse gases in terms of radiative forcing, as aresult of increasing in its precursor emissions since pre-industrial times. Until recently,the ozone radiative forcing calculations were entirely model based, exhibiting high uncertaintiesand a large spread in model values, as shown in the Intergovernmental Panelon Climate Change, Assessment Report 5. Satellite sounders operating in the infrarednow offer the possibility to infer directly the longwave radiative effect (LWRE) of ozone.The hyperspectral measurements allow to retrieve a vertical profile of ozone, and also thevertical distribution of the LWRE, apart from its column integrated value. The separationbetween troposphere and stratosphere allows to better constrain model estimates ofozone radiative forcing, but also support the predictions for its future evolution.In this thesis, a new method for calculating the ozone LWRE is presented, by exploitingthe measurements of the Infrared Atmospheric Sounding Interferometer on board theMetop satellites. The method is based on the calculation of the Instantaneous RadiativeKernel (IRK), which implies the angular integration of the radiance (inthe 9.6 μm band) at the top of the atmosphere using a Gaussian Quadrature. This quantityis transformed into a radiative flux density (the LWRE) by multiplicationwith the ozone profile retrieved by FORLI, for each atmospheric scene. The LWRE calculationmethod is applied to IASI non-cloudy scenes, for day and night, for the periodof 01/10/2007 to 31/12/2016. The results are analyzed separately for the total column ofozone, and for its tropospheric and stratospheric components; they are compared to estimationsdetermined independently from the TES (Tropospheric Emission Spectrometer)measurements on-board Aura, and from three state-of the-art chemistry-climate models.The discussion of the results is focused then on the spatial and temporal variability ofthe LWRE in the troposphere and stratosphere, as well as the on the trends over 9 yearsof measurements.(French)L’ozone est actuellement l’un des gaz à effet de serre les plus importants en terme de forçage radiatif ;sa contribution est liée à l’augmentation des émissions de ses précurseurs depuis l’époque préindustrielle. Jusqu’à récemment, le calcul du forçage radiatif de l’ozone était entièrement basé sur des modèles et était sujet à de grandes incertitudes, qui se révèlent notamment par la large gamme des valeurs calculées et intégrées dans le Cinquième Rapport d’Évaluation du Groupe d’experts intergouvernemental sur l’évolution du climat (GIEC). Les sondeurs embarqués sur des satellites et travaillant dans le domaine de l’infrarouge thermique donnent aujourd’hui la possibilité de directement mesurer l’effet radiatif de l’ozone au niveau de la radiation infrarouge sortante. La possibilité qu’offrent les mesures hyperspectrales pour restituer un profil vertical d’ozone permet par ailleurs de fournir la distribution verticale du forçage radiatif, au-delà se valeur intégrée sur la colonne atmosphérique. La séparation entre la troposphère et la stratosphère est importante en particulier pour contraindre les estimations des modèles mais aussi pour prédire l’évolution future du forçage radiatif. Dans cette thèse, nous présentons une méthode de calcul de l’effet radiatif de l’ozone qui exploite les mesures de l’Interféromètre Atmosphérique de Sondage dans l’Infrarouge (IASI) à bord des satellites Metop en orbite polaire. La méthode se base sur le calcul, pour chaque mesure de IASI, d’une grandeur appelée Instantaneous Radiative Kernel (IRK), impliquant l’intégration angulaire de la radiance (dans la bande d’absorption d’ozone centrée à 9.6µm) au sommet de l’atmosphère via une quadrature de Gauss. Cette quantité est transformée en une densité de flux radiatif (appelée Longwave Radiative Effect, LWRE) par multiplication par le profil d’ozone restitué par le logiciel FORLI, pour la scène atmosphérique en question. La méthode du calcul du LWRE est appliquée aux scènes non nuageuses de IASI, de jour comme de nuit, pour la période du 01/10/2007 au 31/12/2016. Les résultats sont analysés séparément pour la colonne totale d’ozone mais également pour ses composantes troposphériques et stratosphériques ;ils sont comparés aux estimations déterminées de façon indépendantes des mesures de l’instrument TES (Tropospheric Emission Spectrometer) sur AURA. La discussion de nos résultats se focalise ensuite sur la variabilité spatiale et temporelle du LWRE dans la troposphère et la stratosphère ;des résultats préliminaires concernant les tendances sur les 9 années de mesures sont fournis. Le manuscrit est structuré en différentes parties. Après une série de chapitres introductifs décrivant les bases nécessaires à ce travail, nous présentons l’instrument IASI et l’algorithme FORLI dédié à la restitution des concentrations d’ozone. La méthode de calcul du LWRE, au centre de notre travail de recherche, est décrite avec ses fondements mathématiques dans un chapitre dédié. Les distributions spatiales et verticales du LWRE, ainsi que son évolution temporelle sur 9 ans, d’une part pour l’effet radiatif de l’ozone total et d’autre part pour sa contribution troposphérique/stratosphérique sont discutées dans les derniers chapitres, qui incluent également une brève comparaison des estimations du LWRE par trois modèles de chimie-climat différents. / Doctorat en Sciences / info:eu-repo/semantics/nonPublished

Au cours des dernières années, la disponibilité toujours croissante de données de télédétection multi-source de l'océan a été un facteur clé pour améliorer notre compréhension des dynamiques de la surface de l'océan. A cet égard, il est essentiel de mettre au point des approches efficaces pour exploiter ces ensembles de données. En particulier, la décomposition des processus géophysiques en modes pertinents est une question clé pour les problèmes de caractérisation, de prédiction et de reconstruction. Inspirés par des progrès récents en séparation aveugle des sources, nous visons, dans la première partie de cette thèse, à étendre les modèles de séparation aveugle de sources sous contraintes de non-négativité au problème de la caractérisation et décomposition d'opérateurs ou fonctions de transfert entre variables d'intérêt. Nous développons des schémas computationnels efficaces reposant sur des fondations mathématiques solides. Nous illustrons la pertinence des modèles de décomposition proposés dans différentes applications impliquant l'analyse et la prédiction de dynamiques géophysiques. Par la suite, étant donné que la disponibilité toujours croissante d'ensembles de données multi-sources supporte l'exploration des approches pilotées par les données en tant qu'alternative aux formulations classiques basées sur des modèles, nous explorons des approches basées sur les données récemment introduits pour l'interpolation des champs géophysiques à partir d'observations satellitaires irrégulièrement échantillonnées. De plus, en vue de la future mission SWOT, la première mission satellitaire à produire des observations d'altimétrie par satellite complètement bidimensionnelles et à large fauchée, nous nous intéressons à évaluer dans quelle mesure les données SWOT permettraient une meilleure reconstruction des champs altimétriques. / In the last few decades, the ever-growing availability of multi-source ocean remote sensing data has been a key factor for improving our understanding of upper ocean dynamics. In this regard, developing efficient approaches to exploit these datasets is of major importance. Particularly, the decomposition of geophysical processes into relevant modes is a key issue for characterization, forecasting and reconstruction problems. Inspired by recent advances in blind source separation, we aim, in the first part of this thesis dissertation, at extending non-negative blind source separation models to the problem of the observation-based characterization and decomposition of linear operators or transfer functions between variables of interest. We develop mathematically sound and computationally efficient schemes. We illustrate the relevance of the proposed decomposition models in different applications involving the analysis and forecasting of geophysical dynamics. Subsequently, given that the ever-increasing availability of multi-source datasets supports the exploration of data-driven alternatives to classical model-driven formulations, we explore recently introduced data-driven models for the interpolation of geophysical fields from irregularly sampled satellite-derived observations. Importantly, with a view towards the future SWOT mission, the first satellite mission to produce complete two-dimensional wide-swath satellite altimetry observations, we focus on assessing the extent to which SWOT data may lead to an improved reconstruction of altimetry fields.

The Arctic radiation climate is influenced substantially by anthropogenic and natural aerosols. There have been numerous studies devoted to understanding the radiative impacts of anthropogenic aerosols (e.g. those responsible for producing the Arctic haze phenomenon) and natural aerosols (e.g. dust and smoke) on the Arctic environment, but volcanic aerosols have received less attention. Volcanic eruptions occur frequently in the Arctic and have the capacity to be long duration, high intensity events, expelling large amounts of aerosol-sized ash and gases, which form aerosols once in the atmosphere. Additionally, volcanic eruptions deposit ash, which can alter the surface reflectivity, and remain to influence the radiation balance long after the eruptive plume has passed over and dissipated. The goal of this dissertation is to quantify the radiative effects of volcanic aerosols in the Arctic caused by volcanic plumes and deposits onto ice and snow covered surfaces. The shortwave, longwave, and net direct aerosol radiative forcing efficiencies and atmospheric heating/cooling rates caused by volcanic aerosol from the 2009 eruption of Mt. Redoubt were determined by performing radiative transfer modeling constrained by NASA A-Train satellite data. The optical properties of volcanic aerosol were calculated by introducing a compositionally resolved microphysical model developed for both ash and sulfates. Two compositions of volcanic aerosol were considered in order to examine a fresh, ash rich plume and an older, ash poor plume. The results indicate that environmental conditions, such as surface albedo and solar zenith angle, can influence the sign and the magnitude of the radiative forcing at the top of the atmosphere and at the surface. Environmental conditions can also influence the magnitude of the forcing in the aerosol layer. For instance, a fresh, thin plume with a high solar zenith angle over snow cools the surface and warms the top of the atmosphere, but the opposite effect is seen by the same layer over ocean. The layer over snow also warms more than the same plume over seawater. It was found that plume aging can alter the magnitude of the radiative forcing. For example, an aged plume over snow at a high solar zenith angle would warm the top of the atmosphere and layer by less than the fresh plume, while the aged plume cools the surface more. These results were compared with those reported for other aerosols typical to the Arctic environment (smoke from wildfires, Arctic haze, and dust) to demonstrate the importance of volcanic aerosols. It is found that the radiative impacts of volcanic aerosol plumes are comparable to those of other aerosol types, and those compositions rich in volcanic ash can have greater impacts than other aerosol types. Volcanic ash deposited onto ice and snow in the Arctic has the potential to perturb the regional radiation balance by altering the surface reflectivity. The areal extent and loading of ash deposits from the 2009 eruption of Mt. Redoubt were assessed using an Eulerian volcanic ash transport and dispersion model, Fall3D, combined with satellite and deposit observations. Because observations are often limited in remote Arctic regions, we devised a novel method for modeling ash deposit loading fields for the entire eruption based on best-fit parameters of a well-studied eruptive event. The model results were validated against NASA A-train satellite data and field measurements reported by the Alaska Volcano Observatory. Overall, good to moderate agreement was found. A total cumulative deposit area of 3.7 X 10^6 km2 was produced, and loadings ranged from ~7000 ± 3000 gm-2 near the vent to <0.1 ± 0.002 gm-2 on the outskirts of the deposits. Ash loading histories for total deposits showed that fallout ranged from ~5 – 17 hours. The deposit loading results suggest that ash from short duration events can produce regionally significant deposits hundreds of kilometers from the volcano, with the potential of significantly modifying albedo over wide regions of ice and snow covered terrain. The solar broadband albedo change, surface radiative forcing, and snowmelt rates associated with the ash deposited from the 2009 eruption of Mt. Redoubt were calculated using the loadings from Fall3D and the snow, ice, and aerosol radiative models. The optical properties of ash were calculated from Mie theory, based on size information recovered from the Fall3D model. Two sizes of snow were used in order to simulate a young and old snowpack. Deposited ash sizes agree well with field measurements. Only aerosol-sized ashes in deposits were considered for radiative modeling, because larger particles are minor in abundance and confined to areas very close to the vent. The results show concentrations of ash in snow range from ~ 6.9x10^4 – 1x10^8 ppb, with higher values closer to the vent and lowest at the edge of the deposits, and integrated solar albedo reductions of ~ 0 – 59% for new snow and ~ 0 – 85% for old snow. These albedo reductions are much larger than those typical for black carbon, but on the same order of magnitude as those reported for volcanic deposits in Antarctica. The daily mean surface shortwave forcings associated with ash deposits on snow ranged from 0 – 96 Wm-2 from the outmost deposits to the vent. There were no significantly accelerated snowmelts calculated for the outskirts of the deposits. However, for areas of higher ash loadings/concentrations, daily melt rates are significantly higher (~ 220 – 320%) because of volcanic ash deposits.

Οι δασικές πυρκαγιές αποτελούν αναπόσπαστο κομμάτι των Μεσογειακών οικοσυστημάτων επηρεάζοντας το φυσικό κύκλο διαδοχής της βλάστησης, αλλά και τη δομή και λειτουργία τους. Τα τελευταία χρόνια παρατηρείται αύξηση των δασικών πυρκαγιών αυξάνοντας ιδιαίτερα το επιστημονικό ενδιαφέρον. Η χρησιμοποίηση της δορυφορικής τηλεπισκόπησης στη χαρτογράφηση των καμένων εκτάσεων έχει τριάντα χρόνια ιστορία ως εργαλείο χαρτογράφησης αλλά και παρακολούθησης της εξέλιξης των καμένων εκτάσεων. Η χαρτογράφηση των δασικών πυρκαγιών με τη χρήση δορυφορικών δεδομένων είναι και σήμερα ένα εν ενεργεία αντικείμενο έρευνας της τηλεπισκόπησης. Πολλά χαρακτηριστικά παραδείγματα υπάρχουν στη διεθνή βιβλιογραφία με ερευνητικό αντικείμενο τη χαρτογράφηση των καμένων εκτάσεων με τη χρήση πολλαπλών τύπων δορυφορικών δεδομένων, όμως ο αριθμός αυτών που διαπραγματεύονται για την ίδια πυρκαγιά πολλούς τύπους δεδομένων είναι περιορισμένος. Στην παρούσα διδακτορική διατριβή επιχειρείται για πρώτη φορά η χαρτογράφηση των καμένων εκτάσεων με εκτεταμένη χρήση διαφόρων τύπων δορυφορικών εικόνων πολλαπλής φασματικής και χωρικής διακριτικής ικανότητας που έχουν αποκτηθεί για την ίδια πυρκαγιά (Πάρνηθα, 2007). Πιο συγκεκριμένα, αντικείμενο έρευνας αποτέλεσε η χαρτογράφηση των άκαυτων νησίδων εσωτερικά της περιμέτρου της πυρκαγιάς, καθώς και η διερεύνηση των παραγόντων που διαμορφώνουν την ακρίβεια της χαρτογράφησης, η διερεύνηση της ευαισθησίας των τιμών ανάκλασης σε διαφορετικές αναλογίες καμένου/βλάστησης, καθώς και η εφαρμογή και αξιολόγηση διαφόρων δεικτών βλάστησης. Τα δορυφορικά δεδομένα που αξιολογήθηκαν προέρχονται από τους δορυφορικούς ανιχνευτές IKONOS, LANDSAT, ASTER και MODIS. Παράλληλα με τα αρχικά δεδομένα δημιουργήθηκε ένα σύνολο εικόνων πολλαπλής φασματικής και χωρικής κλίμακας. Αρχικά, εφαρμόστηκαν κλασικοί αλγόριθμοι επεξεργασίας εικόνας για τη γεωμετρική, ραδιομετρική και ατμοσφαιρική διόρθωση των δορυφορικών εικόνων. Στη συνεχεία, επεξεργάστηκε η υψηλής ανάλυσης εικόνα IKONOS, η οποία αποτέλεσε τη βάση για τον υπολογισμό του ποσοστού κάλυψης των καμένων εκτάσεων, της βλάστησης και του γυμνού εδάφους σε επίπεδο εικονοστοιχείου. Λαμβάνοντας υπόψη διαφορετικούς συνδυασμούς φασματικών και χωρικών αναλύσεων πραγματοποιήθηκαν συνολικά 420 ταξινομήσεις. Επιπλέον, οι φασματικοί δίαυλοι καθώς και 57 δείκτες βλάστησης που υπολογίστηκαν, συσχετίστηκαν με περιοχές διαφορετικών αναλογιών καμένης και άκαυτης βλάστησης, με σκοπό τη διερεύνηση της ευαισθησίας τους στην εκτίμηση του ποσοστού των καμένων και μη καμένων περιοχών. Συμπερασματικά, η χωρική διακριτική ικανότητα αποδεικνύεται ως ο σημαντικότερος παράγοντας για την αποτύπωση των άκαυτων νησίδων εσωτερικά της περιμέτρου της πυρκαγιάς, ενώ διαπιστώθηκε ότι συσχετίζεται άμεσα με τον αριθμό των χαρτογραφημένων νησίδων. Επιπλέον, το κοντινό και μέσο υπέρυθρο τμήμα του φάσματος αποδείχτηκαν σημαντικά για την εκτίμηση του ποσοστού του καμένου, ενώ το κόκκινο και κοντινό υπέρυθρο για την εκτίμηση του ποσοστού της βλάστησης. Το τελευταίο φαίνεται ότι διαδραματίζει σημαντικό ρόλο στον υπολογισμό του ποσοστού των καμένων εκτάσεων, ενώ το μέσο υπέρυθρο στον υπολογισμό του ποσοστού της βλάστησης. Οι δείκτες βλάστησης ελαχιστοποιούν τις επιδράσεις εξωτερικών παραγόντων, όπως είναι η επίδραση του εδάφους. Έτσι, οι ενδιάμεσες κατηγορίες κρίθηκαν πιο σύμφωνες φασματικά με τις διαφορετικές αναλογίες καμένου/βλάστησης, σε σχέση με τους αρχικούς φασματικούς δίαυλους, βάσει των οποίων υπολογίζονται οι δείκτες. Οι κλασικοί δείκτες, οι οποίοι ενσωματώνουν το κόκκινο και κοντινό υπέρυθρο μήκος κύματος έδειξαν καλύτερη προσαρμογή στην εκτίμηση του ποσοστού της βλάστησης. Αντίθετα, η τροποποιημένη εκδοχή τους, αντικαθιστώντας το κόκκινο με το μέσο υπέρυθρο τμήμα του φάσματος έδειξαν καλύτερη προσαρμογή στην εκτίμηση του ποσοστού των καμένων περιοχών, ταυτόχρονα με την υψηλή προσαρμογή για την εκτίμηση της βλάστησης. Τέλος, πραγματοποιήθηκε η ανασύσταση της πρόσφατης ιστορίας των πυρκαγιών (1984-2011) για την Αττική, εφαρμόζοντας πρόσφατα ανεπτυγμένες (ημι)αυτόματες τεχνικές χαρτογράφησης σε διαχρονικά LANDSAT δορυφορικά δεδομένα μεσαίας χωρικής διακριτικής ικανότητας. Τα αποτελέσματα αυτής της διαδικασίας οδήγησαν στη χαρτογράφηση των περιμέτρων των πυρκαγιών με σχετικά μεγάλη ακρίβεια, ενώ από τα μοντέλα παλινδρόμησης διαπιστώθηκε ότι οι διαφορές μεταξύ της καμένης έκτασης που υπολογίζεται από τα δορυφορικά δεδομένα και αυτά τα οποία καταγράφονται από τη Δασική Υπηρεσία αποδίδονται στον αριθμό των δορυφορικών εικόνων που χρησιμοποιούνται καθώς και στην ημερομηνία απόκτησης της πρώτης δορυφορικής εικόνας. / Forest fires, an integral part of Mediterranean ecosystems, affect the natural cycle of vegetation succession and the ecosystem’s structure and function. Recently, the increment in frequency of fires has increased the concern of the scientific community. The use of remote sensing in burned land mapping has a 30 year long history as tool in mapping and monitoring of forest fire. Despite this long period, burned land mapping using satellite data is still an active research topic in satellite remote sensing. Many characteristic examples of satellite remote sensing studies of burned land mapping and monitoring can be found in the literature, however studies dealing with a multisource data set for the same fire event are limited. The present thesis attempted to map burned surfaces using a multisource satellite data set of multiple spectral and spatial resolution acquired for the same fire event (Parnitha, 2007). In particular, the aims of the thesis were to delineate the unburned patches within fire scar perimeter and explore the factors influence the classification accuracy, to explore the sensitivity of spectral reflectance values to different burn and vegetation ratios, as well as to examine and evaluate some vegetation indices. The satellite data used were acquired from IKONOS, LANDSAT, ASTER and MODIS. Along with the basic data set, a spatially degraded satellite data over a range of coarser resolutions were created. Firstly, classical image processing algorithms were applied to correct geometrically, radiometrically and atmospherically the satellite images used. The pan-sharpened IKONOS served as the basis to estimate the percent of cover of burned areas, vegetation and bare land, at pixel level. Totally 420 classifications have been implemented considering different combinations of spectral and spatial resolutions. Additionally, the spectral bands and 57 versions of some classical vegetation indices were correlated with different burned and vegetation ratios in order to explore their sensitivity. Conclusively, spatial resolution is the most important factor for the delineation of the unburned patches within the fire scar perimeter, while proved to be strongly correlated with the number of the mapped islands. Moreover, the near and middle infrared channels were the most important ones to estimate the percentage of burned area, while the red and near infrared were the most important channels to estimate the percentage of vegetation. The latter, seemed to play a more significant role in estimating the percent of burned area while the middle infrared seemed to play a more significant role in estimating the percent of vegetation. Vegetation indices are less sensitive to external parameters of the vegetation by minimizing external effects, such as soil impact. Thus, the semi-burned classes were spectrally more consistent to their different fractions of scorched and non-scorched vegetation, than the original spectral channels based on which these indices are estimated. The classical indices, which incorporate the red-near infrared space showed better performance to estimate the percent of the vegetation. In contrast, the modified version of the classical indices, by replacing the red with the middle infrared channel showed the highest performance to estimate the percent of burned areas, apart from the high performance in the estimation of the vegetation. Finally, in the present thesis maps with the reconstruction of the recent fire history of Attica region were created, in a spatially explicit mode using (semi)automated image processing techniques in a series of multi-temporal medium-resolution LANDSAT images. The results showed that the fire-scar perimeters were captured with considerably high accuracy, while regression modeling showed that the differences between the area burned estimated from satellite data and that recorded by the forest service can be explained by the number of satellite images used followed by the acquisition date of the first image.

The current study focuses on the phenomenon, mostly accounted within the past recent time, of the algae blooms (chlorophyll burst) in the area of the North Aegean Sea. The study attempts to coincide and amplify the approach of Satellite Remote Sensing monitoring, as means of applied oceanographic methods, in order for possible seasonal, spatio-temporal trends of this phenomenon to be identified, thus making the correlation of the indices-variations, though interdisciplinary, to be explained to an extend plainly, in terms of ‘why’ and ‘why-then’ they occur. The North Aegean Sea is directly influenced by the outflow of the Black Sea water masses, through the Dardanelles Strait. Secondary, riverine discharge is into account, along with special hydrodynamic characteristics of the basin. This Black Sea contribution to the North Aegean basin is cold, brackish and rather rich in biomass and nutrients and via the eutrophic blooms, fluctuate the relative meso-poor nutrient character of the basin. The environmental impacts and causes of the occurrences have a multidisciplinary analysis. They affect local ecology systems, water quality, coastal regions, the ichtyo-stock, the eco-balance on food-dependable species and ultimately the human health. The current study leans emphasis on the meteorological-oceanographic analysis for the algae blooms in the North Aegean Sea, depending on the use of satellite derived data and optical color imaginary, concerning the area under study. The preliminary concern, along with secondary conclusions, among the variable instability of the local biogeochemical recycling of the phenomenon, the prolonged temporal time of its dispersion and its correlation with surface winds and meteo-characteristics, was verified. Data from Giovanni, that is a Web-based application developed by the GES DISC (Goddard Earth Sciences Data and Information Services Center) Interactive Online Visualization ANd aNalysis Infrastructure-NASA, where used for the analysis, in order for possible correlations between oceanographic and meteorological variables to be identified, such as: Chlorophyll-a concentrations, Precipitations rates, Euphotic Zone Depth, Colored Dissolved Organic Matter, Absorption coefficient for phytoplankton, Sea Level Pressure, Surface Pressure and Northwards wind component. / --

The geometry, deformation mechanism and kinematics of the S&uuml / rg&uuml / Fault Zone is investigated by using remotely sensed data including Landsat TM and ASTER imagery combined with SRTM, and stereo-aerial photographs. They are used to extract information related to regional lineaments and tectono-morphological characteristics of the SFZ. Various image processing and enhancement techniques including contrast enhancement, PCA, DS and color composites are applied on the imagery and three different approaches including manual, semi automatic and automatic lineament extraction methods are followed. Then the lineaments obtained from ASTER and Landsat imagery using manual and automatic methods are overlaid to produce a final lineaments map. The results have indicated that, the total number and length of the lineaments obtained from automatic is more than other methods while the percentages of overlapping lineaments for the manual method is more than the automatic method which indicate that the lineaments from automatic method does not discriminate man made features which result more lineaments and less overlapping ratio with respect to final map. It is revealed from the detail analysis that, the SFZ displays characteristic deformation patterns of strike-slip faults, such as pressure ridges, linear fault controlled valleys, deflected stream courses, rotated blocks and juxtaposition of stratigraphical horizons in macroscopic scale. In addition to these, kinematic analyses carried out using fault slip data indicated that the S&uuml / rg&uuml / Fault Zone is dextral strike-slip fault zone with a reverse component of slip and cumulative displacement along the fault is more than 2 km.

nÃo hà / A observaÃÃo da superfÃcie terrestre por meio de satÃlites em Ãrbita de nosso planeta tornou-se corriqueira no mundo contemporÃneo. As inferÃncias de variÃveis ambientais diversas feitas a partir de imagens e dados fornecidos por satÃlites cada vez mais aumentam em qualidade e aplicabilidade de maneira que um nÃmero crescente de hidrologistas, meteorologistas, climatologistas e outros profissionais e leigos em geral fazem uso intensivo delas em estudos e pesquisas, em polÃticas governamentais ou na tomada de decisÃo. Uma dessas variÃveis à a umidade superficial do solo, que representa uma importante componente do ciclo hidrolÃgico terrestre, essencial em vÃrios processos naturais ambientais e cujo conhecimento à importante no gerenciamento dos recursos hÃdricos e terrestres, gerenciamento agrÃcola e na modelagem do meio ambiente e agrÃcola. As informaÃÃes derivadas de satÃlites, apesar de ainda apresentarem algumas limitaÃÃes tÃcnicas, podem facilitar bastante o monitoramento ambiental ao se tornarem, muitas vezes, mais Ãgeis e mais econÃmicas do que mediÃÃes locais in situ. Em paÃses em desenvolvimento e de limitados recursos financeiros, tais como o nosso, a informaÃÃo por satÃlites cresce em valor. No Estado do CearÃ, isso desponta ainda mais em virtude das suas dificuldades econÃmicas e sociais. Em vista disso, à proposta, neste trabalho, a aplicaÃÃo nesse estado do Nordeste de um mÃtodo de inferÃncia, por satÃlite, do estado geral da umidade superficial do solo expresso pelo Ãndice de Seca Temperatura-VegetaÃÃo (ISTV), que à indicativo do grau da umidade, estando a ela relacionado. Esse Ãndice à obtido a partir da combinaÃÃo de informaÃÃes da Temperatura da SuperfÃcie Continental (TSC) e do Ãndice de VegetaÃÃo por DiferenÃa Normalizada (IVDN), inferidos por meio de imagens no visÃvel e no infravermelho que podem ser fornecidas por satÃlites meteorolÃgicos operacionais, de Ãrbita polar, tais como os da sÃrie NOAA (National Oceanic and Atmospheric Administration, EUA). No mÃtodo, foi escolhido, da literatura cientÃfica, um algoritmo de cÃlculo da TSC que apresenta certa facilidade de uso, sendo diretamente dependente da FraÃÃo de Cobertura de VegetaÃÃo (FCV) e que pode fornecer boas inferÃncias dessa temperatura. Nesse algoritmo, foram testadas, de forma inÃdita, algumas diferentes formulaÃÃes da FCV encontradas na literatura especializada, representando uma delas o estado da arte no assunto. Foram usadas imagens provenientes do satÃlite NOAA-17, recepcionadas na FUNCEME, e um software especÃfico, dessa FundaÃÃo, para se processar as imagens e implementar a metodologia abordada. Alguns testes foram feitos para duas regiÃes relativamente pequenas do semiÃrido cearense, com destaque para uma delas englobando a Bacia Experimental de Aiuaba (BEA), comparando-se as informaÃÃes do satÃlite NOAA-17 com dados in situ (provenientes de sondas no solo) e com dados advindos dos satÃlites ambientais Terra (dados de TSC, disponÃveis na Internet) e Aqua (dados de umidade superficial do solo). Procurou-se mostrar as diferenÃas qualitativas entre os mapeamentos obtidos, de umidade superficial do solo, e entre estes e os oferecidos pela modelagem em geral. Os resultados encontrados mostraram-se promissores para a utilizaÃÃo no territÃrio cearense do ISTV (no modelo trapezoidal) por meio de satÃlites NOAA, com o algoritmo de Kerr para o cÃlculo da TSC e com a FCV dada pelo Scaled Difference Vegetation Index (SDVI), com o fim de se estimar o estado geral da umidade superficial do solo sobre grandes Ãreas. Entretanto, recomenda-se mais validaÃÃo local posterior do mÃtodo usado, para detecÃÃo de possÃveis erros ou limitaÃÃes nÃo vislumbradas nestes primeiros testes, visando sua definitiva aplicaÃÃo operacional no Cearà e mesmo no semiÃrido do Nordeste.

Measuring the composition of the planetary boundary layer is essential for monitoring pollutants and for understanding their impact on environment and health. Nadir satellite remote sensing is particularly appealing to sound this part of the atmosphere, but is however challenging because pollutants concentrations are generally weak and confined in a small part of the atmospheric column. Among the sounders currently in orbit, those operating in the thermal infrared have usually their maximum sensitivity in the mid-troposphere, and are thought to be inadequate to measure the near-surface atmospheric composition. Their sensitivity to this part of the atmosphere is indeed generally limited by low temperature contrast (called thermal contrast) between the ground and the air above it. Shortly before the beginning of this PhD, this has however been challenged with different studies, which have shown the possibility to measure air pollution with thermal infrared sounders in case of high thermal contrast conditions. This was especially demonstrated with the measurement of ammonia global distribution using the Infrared Atmospheric Sounding Interferometer (IASI). This work aims at fully exploring the capabilities of thermal infrared sounders to sound the near-surface atmospheric composition. It mainly focuses on the observations of the IASI instrument, and addresses the following questions: where and when is IASI sensitive to the near-surface atmosphere? How large and how variable is the sensitivity to near-surface pollutants? What are the parameters that drive this variability? The answers to these questions are looked at for two pollutants: sulphur dioxide (SO2) and carbon monoxide (CO), and are obtained through a series of different analyses. SO2 is the first constituent on which this work focuses. The retrieval of its near-surface concentration is first of all attempted in an area surrounding the industrial area of Norilsk. This region, well-known for the extraction of heavy metals and its extremely high levels of pollution, encounters large temperature inversions in winter, which trap SO2 close to the ground. By exploiting these (corresponding to high negative thermal contrast), we show that it is possible to retrieve the surface SO2 concentrations in the region. This is done using a simplified version of the optimal estimation method, based on the use of a total measurement error covariance matrix. Further, we show that the surface SO2 concentration retrieval using the ν3 band is limited, in addition to thermal contrast, by the strong water (H2O) absorption, which renders the lowest atmosphere opaque in this spectral range in case of large humidity. Two conditions are therefore shown to be required to monitor near-surface SO2 in the ν3 band: large thermal contrast and low surface humidity. These findings are confirmed with the retrieval of SO2 at global scale, performed using a newly developed retrieval scheme based on the conversion of radiance indexes into SO2 columns using look-up-tables. It is composed of two successive steps: 1) the determination of the altitude of SO2 and the selection of low plumes (below 4 km), 2) for the selected observations, the conversion of radiance indexes into integrated SO2 0–4 km columns. The distributions and time series so obtained are used to better characterise the variability of IASI sensitivity to surface SO2 in the ν3 band at the global scale, and more particularly, in terms of thermal contrast strength and total column of H2O.The characterisation of IASI sensitivity to CO is realised in a second part of the work. Radiative transfer simulations are conducted first to determine the possibility to detect enhancement in CO near-surface concentrations with IASI. The framework of the optimal estimation is then used to investigate the capability of IASI to decorrelate, as a function of thermal contrast, the CO concentration in the low troposphere from that in the high troposphere. Finally, comparisons of IASI CO observations with co-located aircraft and ground-based measurements are shown to confirm with real data how IASI sensitivity to near-surface CO varies in terms of thermal contrast conditions, and to which extent it allows determining the CO abundance in case of high pollution. / Mesurer la composition de la couche limite atmosphérique depuis les satellites est essentiel pour comprendre l’impact des polluants sur l’environnement global et sur la santé. Parmi les sondeurs actuellement en orbite, ceux opérant dans l’infrarouge thermique sont souvent considérés comme inadéquats pour cet objectif, leur sensibilité à l’atmosphère de surface étant généralement limitée par de faibles contrastes de température (appelés contrastes thermiques, TC) entre le sol et l’air au-dessus. Différentes études récentes ont cependant montré la possibilité de mesurer la pollution de l’air avec ce type de sondeur dans des conditions de TC élevé.Ce travail a pour objectif de redéfinir la capacité des sondeurs opérant dans l’infrarouge thermique à mesurer la composition de l’atmosphère de surface. Il se focalise sur les observations de l’instrument IASI (Interféromètre Atmosphérique de Sondage Infrarouge), et tente de répondre, pour les deux polluants que sont le dioxyde de soufre (SO2) et le monoxyde de carbone (CO), aux questions suivantes :Où et quand IASI est-il sensible à l’atmosphère de surface ?Quels sont les paramètres qui influencent cette sensibilité et dans quelle mesure?Dans une première partie, la thèse se focalise sur l’ajustement des concentrations de SO2 de surface pour la région industrielle de Norilsk, connue pour son niveau de pollution élevé. Nous montrons qu’il y est possible de restituer les concentrations de surface de SO2 en hiver, en exploitant les larges inversions de température (TC négatifs) qui s’y développent. Les restitutions reposent sur une version simplifiée de la méthode de l’estimation optimale, utilisant une matrice complète de l’erreur de mesure. En plus du TC, nous montrons que l’ajustement dans la bande ν3 du SO2 est également limité par la forte absorption de la vapeur d’eau (H2O), qui rend les basses couches de l’atmosphère opaques. La nécessité de combiner des TCs élevés et une faible humidité pour permettre la mesure du SO2 en surface est confirmée par une analyse à l’échelle globale, utilisant une méthode basée sur la mesure d’indices de radiance et leur conversion en colonnes de SO2 à l’aide de tables pré-calculées. Composée de 2 étapes, cette méthode identifie et sélectionne d’abord les panaches situés sous 4 km ;elle convertit ensuite les indices de radiance en colonnes de SO2 intégrées entre 0 et 4 km. Les distributions et séries temporelles obtenues sont utilisées pour caractériser, en termes de valeurs de TC et de colonnes totales d’H2O, la variabilité de la sensibilité de IASI au SO2 de surface dans la bande ν3.Dans la seconde partie du travail, des simulations de transfert radiatif sont entreprises pour déterminer la possibilité de détecter avec IASI des augmentations de la concentration de CO dans l’atmosphère de surface. Le formalisme de l’estimation optimale est aussi utilisé pour analyser l’influence du TC sur la capacité de IASI à décorreler les concentrations du CO dans la basse et la haute troposphère. Finalement, des comparaisons entre les concentrations de CO restituées des mesures IASI sous différentes conditions de TC et de pollution et celles mesurées par avions et par des stations au sol complètent la caractérisation. / Doctorat en Sciences / info:eu-repo/semantics/nonPublished

Les milieux humides sont menacés par le changement climatique et l'anthropisation des milieux naturels. La télédétection est un moyen efficace de suivre des variables environnementales sur de grands espaces. Cependant, lorsqu’il s’agit de l’étude de la dynamique hydrologique, une résolution temporelle importante est indispensable. Or celle-ci est difficilement accessible par l'imagerie optique satellitaire du fait de l’important couvert nuageux qui masque le sol. Les capteurs radars, travaillant dans le domaine des micro-ondes, sont tout particulièrement adaptés à la caractérisation des dynamiques hydrologiques grâce à la sensibilité de leurs mesures en présence d’eau et ce quelque soit la végétation en place. Il en découle que toutes les acquisitions Radar à Synthèse d’Ouverture (RSO) sont exploitables, acquises de jour comme de nuit, quel que soit le couvert nuageux.Récemment la télédétection radar satellitaire a vécu une véritable révolution grâce au lancement du satellite Sentinel-1A en 2014 suivi de son jumeaux Sentinel-1B deux ans plus tard par l'Agence Spatiale Européenne dans le cadre du programme Copernicus. Ces capteurs acquièrent des données en bande C (λ = 5,6 cm) sur toute l'Europe chaque 12 jours par satellite et leur diffusion est libre et gratuite pour tous. Le présent travail de thèse vise à évaluer le potentiel de ces données à haute résolution temporelle pour le suivi des surfaces d'eau et des milieux humides.Dans une première partie consacrée à la cartographie des surfaces d'eau, nous avons identifié une confusion la réponse radar en bande C des surfaces d'eau et celle de certains sols nus. Nous avons alors montré que la période hivernale est celle qui présente le moins d’ambiguïté et que la polarisation VH est la plus adaptée à la cartographie des surfaces en eau. Quatre méthodes de détection des zones en eau ont été comparées, il résulte que l’utilisation de méthodes non-supervisées sans données a priori n'est pas envisageable et que les méthodes prenant en compte le voisinage spatial donnent de meilleurs résultats. Un filtrage temporel a été mis au point et a permis d'améliorer la détection et de s'affranchir des confusions entre sols nus et surfaces d'eau permanentes. Les surfaces d'eau de plus de 0,5 ha ont plus de 80 % de chances d'être détectées.Un second volet de cette thèse est consacré au suivi d'une zone humide prairiale par télédétection radar. L'utilisation d'images pleinement polarimétriques a montré que la configuration de polarimétrie partielle VV/VH disponible sur le capteur de Sentinel-1 permet de caractériser l'inondation prairiale avec ou sans végétation. Une méthode prenant en compte l'information de voisinage temporel a permis de traiter une série de 14 images Sentinel-1 pour obtenir 14 cartes d'inondation pour l’année 2015. Une estimation de la précision à l'échelle intra-parcellaire a été mise au point, il apparaît que si la précision est relativement bonne (80 %), le rappel est assez bas (40 %). Cette méthode permet d'établir des bilans d'évolution intra- et inter-annuels.Cette thèse a montré le potentiel de l'utilisation d'images radar à haute résolution temporelle tant pour la cartographie des surfaces en eau que pour le suivi d'une zone humide prairiale / Wetlands are threatened by climate change and the anthropization of natural environments. Satellite remote sensing is useful for environmental monitoring at large areas. However, when it comes to the study of hydrological dynamics, a significant temporal resolution is essential. The latter is difficult to reach with optical satellite imagery because of the cloud cover that masks the ground. Radar sensors are well suited to the characterization of hydrological dynamics thanks to the sensitivity of their measurements in the presence of water, whatever the vegetation in place. As a result, all Synthetic Aperture Radar (SAR) acquisitions are available, both day and night, regardless of cloud cover.Satellite radar remote sensing has gone through a revolution with the launch of the Sentinel-1A satellite, followed by its twins Sentinel-1B by the European Space Agency as part of the Copernicus program in 2014. These sensors acquire C-band data (λ = 5.6 cm) on a regular basis on Europe and their distribution is free for all users. Their temporal frequency initially of 12 days has decreased to 6 days from the end of 2016. This work aims at evaluating the potential of these data with high temporal resolution for the monitoring of water bodies and wetlands.The first part of this thesis focuses on water bodies mapping. We found confusion in the C-band radar response between water surfaces and that of some bare soils. We showed that the winter period is the least ambiguous and that the VH polarization is the most suitable for the mapping of water surfaces. Four methods of water detection have been compared. It appears that the use of unsupervised methods without a priori data is not conceivable and that the methods taking into account the spatial neighborhood give better results. Temporal filtering has been developed and has improved detection and avoided confusion between bare soil and permanent water surfaces. Water surfaces of more than 0.5 ha are more than 80% likely to be detected.A second part of this thesis is devoted to the monitoring of wet grasslands by radar remote sensing. The use of fully polarimetric data has shown that the VV/VH partial polarimetry configuration available on the Sentinel-1 sensor is able to characterize the prairial floods with or without vegetation. A method taking into account the temporal neighborhood allowed to process a series of 14 Sentinel-1 images to obtain 14 flood maps. The accuracy of floods maps at the intra-parcel scale has been estimated, it appears that if the precision is relatively good (80%), but the recall is rather low (40%). This method allow to establish intra- and inter-annual monitoring.This thesis has shown the potential of high temporal resolution radar images for the mapping of the water surfaces and for the monitoring of a wetland meadow