<p>Emerging mobile mapping systems include a wide range of platforms, for instance, manned aircraft, unmanned aerial vehicles (UAV), terrestrial systems like trucks, tractors, robots, and backpacks, that can carry multiple sensors including LiDAR scanners, cameras, and georeferencing units. Such systems can maneuver in the field to quickly collect high-resolution data, capturing detailed information over an area of interest. With the increased volume and distinct characteristics of the data collected, practical quality control procedures that assess the agreement within/among datasets acquired by various sensors/systems at different times are crucial for accurate, robust interpretation. Moreover, the ability to derive semantic information from acquired data is the key to leveraging the complementary information captured by mobile mapping systems for diverse applications. This dissertation addresses these challenges for different systems (airborne and terrestrial), environments (urban and rural), and applications (agriculture, archaeology, hydraulics/hydrology, and transportation).</p> <p>In this dissertation, quality control procedures that utilize features automatically identified and extracted from acquired data are developed to evaluate the relative accuracy between multiple datasets. The proposed procedures do not rely on manually deployed ground control points or targets and can handle challenging environments such as coastal areas or agricultural fields. Moreover, considering the varying characteristics of acquired data, this dissertation improves several data processing/analysis techniques essential for meeting the needs of various applications. An existing ground filtering algorithm is modified to deal with variation in point density; digital surface model (DSM) smoothing and seamline control techniques are proposed for improving the orthophoto quality in agricultural fields. Finally, this dissertation derives semantic information for diverse applications, including 1) shoreline retreat quantification, 2) automated row/alley detection for plant phenotyping, 3) enhancement of orthophoto quality for tassel/panicle detection, and 4) point cloud semantic segmentation for mapping transportation corridors. The proposed approaches are tested using multiple datasets from UAV and wheel-based mobile mapping systems. Experimental results verify that the proposed approaches can effectively assess the data quality and provide reliable interpretation. This dissertation highlights the potential of modern mobile mapping systems to map challenging environments for a variety of applications.</p>

Robust detection, localization, and tracking of objects are essential for autonomous driving. Computer vision has largely driven development based on camera sensors in recent years, but 3D localization from images is still challenging. Sensors such as LiDAR or RADAR are used to compute depth; each having its own advantages and drawbacks. The main idea of the project is to be able to mix images from the camera and RADAR detections in order to estimate depths for the objects appearing in the images. Fusion strategies can be considered the solution to give a more detailed description of the environment by utilizing both the 3D localization capabilities of range sensors and the higher spatial resolution of image data. The idea is to fuse 3D detections from the RADAR onto the image plane, this requires a high level of synchronization of the sensors and projections of the RADAR data on the required image. / Robust detektering, lokalisering och spårning av objekt är avgörande för autonom körning. Datorseende har till stor del drivit utvecklingen baserad på kamerasensorer de senaste åren, men 3D-lokalisering från bilder är fortfarande utmanande. Sensorer som LiDAR eller RADAR används för att beräkna djup; var och en har sina egna fördelar och nackdelar. Huvudtanken med projektet är att kunna blanda bilder från kameran och RADAR-detektioner för att uppskatta djup för de objekt som förekommer i bilderna. Fusionsstrategier kan anses vara lösningen för att ge en mer detaljerad beskrivning av miljön med både 3D-lokaliseringsförmågan hos avståndssensorer och den högre rumsliga upplösningen av bilddata. Tanken är att smälta samman 3D-detektioner från RADAR till bildplanet, detta kräver en hög nivå av synkronisering av sensorerna och projektioner av RADAR-data på den önskade bilden.

At Halmstad University a project was developed to provide recommendations forupgrading and downgrading the cloud resource app service plan based on the customersusage over the last 30 days. In today’s day and age, cloud resources and services are oftenquite expensive and offers a variety of different plans which can make it overwhelmingfor the customer to easily choose which tier they need for their plan. The result of thisscript indicate that the cloud users should consider changing subscription tier based onhow the historical data of their usage of the plan has looked like during the last 30 days.The proposed algorithm suggests an upgrade of a tier if the plan is overutilized andsuggest a downgrade of a tier if the plan is underutilized. The developed PowerShell codeuses the First-Fit and the Rule-based algorithmic approach from the related workresearched in the paper. The result found was that the code was able to give suitablerecommendations to scale up and down tiers for plans which were under and overutilizedbased on the percentual utilization rules set up and Legacy/DEV SKU mapping. Theresults obtained showed that the suggested plan can reduce costs by up to 30% and giveroughly 438.2% more performance per $USD spent. / Vid Högskolan i Halmstad utvecklades ett projekt för att ge förslag på uppgraderingaroch nedgraderingar av molnresursern app service plan baserat på användarens senaste 30dagars användning. Då dagens molnresurser och tjänster ofta är dyra och erbjuder ettöverflöd av planer, kan det vara förvirrande för användare att välja rätt nivå för sinabehov. Projektet föreslår att användarna ska överväga att byta plan beroende på hur denhistoriska datan har sett ut för planens användning, där en uppgradering rekommenderasom tjänsten är överanvänd och en nedgradering om planen är underanvänd. Denutvecklade PowerShell koden använder sig av First-fit och det regelbaserade algoritmtypen som utvecklades med inspiration från litteraturstudien. Resultatet av projektetindikerar att koden kunde ge optimala upp och ned skalnings rekommendationer beroendepå de olika procentuella trösklarna satta samt mappningen av Legacy och utvecklingstiers. Analyseringen av resultatet pekar på att det går att spara runt 30% på app serviceplan kostnaderna samt att app service planerna får 438,2% mer prestanda per spenderad$USD i jämförelse med nuvarande planen.

Der Beitrag beschäftigt sich mit dem Handscanner ZEB-REVO der Firma GeoSLAM. Es werden die Handhabung der Hardware im untertägigen Einsatz und die Weiterverarbeitung der Punktwolken für Anwendungen im Bergbau näher betrachtet. Die Notwendigkeit der Referenzierung der Punktwolken und eine Möglichkeit diese umzusetzen, werden dargelegt. Über den Vergleich der Daten mit Punktwolken von terrestrischen Laserscannern der Firma Riegl in der Software RiScanPro werden Genauigkeitsuntersuchungen angestellt, die dem Anwender die Grenzen des Systems aufzeigen. Schließlich führen die angestellten Untersuchungen zu einer kritischen Bewertung des Systems. / This contribution addresses practical aspects, abilities and limitations in using the ZEBREVO hand-held scanner from GeoSLAM for underground mine mapping. Besides mapping activities, also post-processing of generated point clouds and requirements for georeferencing are discussed. An accuracy assessment is presented by the means of a point cloud comparison, generated by a terrestrial laser scanner from Riegl. Results demonstrate the technical ability and also the limitations of the system ZEB-REVO. Concluding, a critical evaluation of the system is presented.

L'hydrogène moléculaire diffus et froid peut être l'un des candidats ultimes à la composante baryonique cachée de la Voie Lactée. Nous décrivons une nouvelle voie de recherche de matière transparente dans le disque et le halo galactiques, qui exploite les effets de diffraction et de réfraction de la lumière des étoiles d'arrière-plan. En simulant le retard de phase induit par un milieu turbulent, nous avons calculé la figure d'éclairement sur la terre d'une source étendue pour une bande passante donnée. Nous montrons que dans les cas favorables, la luminosité apparente d'une étoile d'arrière-plan peut être soumise à des fluctuations stochastiques de l'ordre de quelques pour cent sur une échelle de temps caractéristique de quelques minutes. Nous avons recherché de tels effets de scintillation, induits par du gaz moléculaire de nébuleuses visibles (sombres), ainsi que par d'hypothétiques (invisibles) clumpuscules d'hydrogène moléculaire froid du halo, pendant deux nuits avec le détecteur infra-rouge SOFI au foyer du télescope NTT de l'ESO. Parmi les quelques milliers d'étoiles surveillées, nous avons détecté un objet dont les variations sont compatibles avec un fort effet de scintillation à travers une structure turbulente de la nébuleuse B68. Comme par ailleurs aucun effet de scintillation n'a été trouvé vers le Petit Nuage de Magellan, nous sommes en mesure d'établir des limites supérieures sur la contribution des clumpuscules de gaz à la masse du halo galactique. Nous montrons qu'une surveillance à cadence élevée dans la bande visible avec un télescope de diamètre supérieur à quatre mètres équipé d'une caméra à lecture rapide devrait permettre, avec une exposition de quelque millions (d'heures x étoiles), de quantifier ou de borner d'une façon très significative la contribution du gaz moléculaire turbulent au halo Galactique. / Cool molecular hydrogen H2 may be the ultimate possible constituent to the Milky-Way missing baryon. We describe a new way to search for such transparent matter in the Galactic disc and halo, through the diffractive and refractive effects on the light of background stars. By simulating the phase delay induced by a turbulent medium, we computed the corresponding illumination pattern on the earth for an extended source and a given passband. We show that in favorable cases, the light of a background star can be subjected to stochastic fluctuations of the order of a few percent at a characteristic time scale of a few minutes. We have searched for scintillation induced by molecular gas in visible dark nebulae as well as by hypothetical halo clumpuscules of cool molecular hydrogen (H2_He) during two nights, using the NTT telescope and the IR SOFI detector. Amongst a few thousands of monitored stars, we found one light-curve that is compatible with a strong scintillation effect through a turbulent structure in the B68 nebula. Because no candidate were found toward the SMC, we are able to establish upper limits on the contribution of gas clumpuscules to the Galactic halo mass. We show that the short time-scale monitoring of a few 10^6 star _ hour in the visible band with a >4 m telescope and a fast readout camera should allow one to interestingly quantify or constrain the contribution of turbulent molecular gas to the Galactic halo.

Diese Dissertation beschäftigt sich mit regionaler Klimamodellierung über Südamerika, der Analyse von Modellsensitivitäten bezüglich Wolkenparametrisierungen und der Entwicklung neuer Methoden zur Modellevaluierung mithilfe von Klimanetzwerken. Im ersten Teil untersuchen wir Simulationen mit dem COnsortium for Small scale MOdeling model in CLimate Mode (COSMO-CLM) und stellen die erste umfassende Evaluierung dieses dynamischen regionalen Klimamodells über Südamerika vor. Dabei untersuchen wir insbesondere die Abhängigkeit simulierter tropischer Niederschläge von Parametrisierungen subgitterskaliger cumuliformer und stratiformer Wolken und finden starke Sensitivitäten bezüglich beider Wolkenparametrisierungen über Land. Durch einen simultanen Austausch der entsprechenden Schemata gelingt uns eine beträchtliche Reduzierung von Fehlern in klimatologischen Niederschlags- und Strahlungsmitteln, die das COSMO-CLM über tropischen Regionen für lange Zeit charakterisierten. Im zweiten Teil führen wir neue Metriken für die Evaluierung von Klimamodellen bezüglich räumlicher Kovariabilitäten ein. Im Kern bestehen diese Metriken aus Unähnlichkeitsmaßen für den Vergleich von simulierten mit beobachteten Klimanetzwerken. Wir entwickeln lokale und globale Unähnlichkeitsmaße zum Zwecke der Darstellung lokaler Unähnlichkeiten in Form von Fehlerkarten sowie der Rangordnung von Modellen durch Zusammenfassung lokaler zu globalen Unähnlichkeiten. Die neuen Maße werden dann für eine vergleichende Evaluierung regionaler Klimasimulationen mit COSMO-CLM und dem Statistical Analogue Resampling Scheme über Südamerika verwendet. Dabei vergleichen wir die sich ergebenden Modellrangfolgen mit solchen basierend auf mittleren quadratischen Abweichungen klimatologischer Mittelwerte und Varianzen und untersuchen die Abhängigkeit dieser Rangfolgen von der betrachteten Jahreszeit, Variable, dem verwendeten Referenzdatensatz und Klimanetzwerktyp. / This dissertation is about regional climate modeling over South America, the analysis of model sensitivities to cloud parameterizations, and the development of novel model evaluation techniques based on climate networks. In the first part we examine simulations with the COnsortium for Small scale MOdeling weather prediction model in CLimate Mode (COSMO-CLM) and provide the first thorough evaluation of this dynamical regional climate model over South America. We focus our analysis on the sensitivity of simulated tropical precipitation to the parameterizations of subgrid-scale cumuliform and stratiform clouds. It is shown that COSMO-CLM is strongly sensitive to both cloud parameterizations over tropical land. Using nondefault cumulus and stratus parameterization schemes we are able to considerably reduce long-standing precipitation and radiation biases that have plagued COSMO-CLM across tropical domains. In the second part we introduce new performance metrics for climate model evaluation with respect to spatial covariabilities. In essence, these metrics consist of dissimilarity measures for climate networks constructed from simulations and observations. We develop both local and global dissimilarity measures to facilitate the depiction of local dissimilarities in the form of bias maps as well as the aggregation of those local to global dissimilarities for the purposes of climate model intercomparison and ranking. The new measures are then applied for a comparative evaluation of regional climate simulations with COSMO-CLM and the STatistical Analogue Resampling Scheme (STARS) over South America. We compare model rankings obtained with our new performance metrics to those obtained with conventional root-mean-square errors of climatological mean values and variances, and analyze how these rankings depend on season, variable, reference data set, and climate network type.

Evapotranspiration is a nexus for planetary energy and carbon cycles, as yet poorly constrained. Here I use stable isotopes of oxygen and hydrogen to partition flux of water due to plant transpiration from the direct evaporative flux from soils, water bodies and plant. The study areas, Langat and Kelantan watersheds represent examples of domains dominated by the respective Southwest and Northeast monsoons on the two sides of the main orographic barrier (Titiwangsa mountain range). Mean annual rainfall for the Langat watershed, obtained from 30 years of hydrological data, is 2145 ± 237 mm. Tentatively, 48% of this precipitation returns to the atmosphere via transpiration (T), with 33% partitioned into discharge (Q), 8% into interception (In), and 11% into evaporation (Ed). In the Kelantan watershed, the mean annual rainfall, also based on the 30 year hydrological data, is 2383 ± 120 mm. Similar to Langat, the T accounts for 43% of precipitation (P), 45% is discharged into South China Sea (Q), 12% partitioned into interception (In) and tentatively 0% for evaporation (Ed). Ed for the Langat watershed represents only a small proportion in terms of volumetric significance, up to almost ~11% with strong effect on the isotopic fingerprints of waters associated with the summer Southwest Monsoon (SWM). Note, however, that insignificant Ed for the Kelantan watershed may be an artefact of rain and river water sampling at only coastal downstream portion of the watershed. High humidity (80%) also was recorded for the Malaysian Peninsula watershed. T appropriates about half of all solar energy absorbed by the continents, here ~1000*103 g H2O m-2 yr-1 similar to other tropical regions at 900-1200*103 g H2O m-2 yr-1. The associated carbon fluxes are ~ 1300 g C m-2yr-1, independent of P. Vegetation responses to solar irradiance, via T and photosynthesis reflects the importance of stomatal regulation of the water and carbon fluxes. In order to maintain high transpiration in the tropical region, “constant” water supply is required for continuous pumping of water that delivers nutrients to the plant, suggesting that water and carbon cycle are co-driven by the energy of the sun. The existence of the water conveyor belt may be precondition for nutrient delivery, hence operation of the carbon cycle. Potentially, this may change our perspective on the role that biology plays in the water cycle. In such perspective, the global water cycle is the medium that redistributes the incoming solar energy across the planet, and the anatomical structures of plants then help to optimize the loop of energy transfer via evaporation and precipitation in the hydrologic cycle. The main features of aquatic geochemistry of the Langat and Kelantan rivers inferred from the Principal Component Analysis are controlled by three components that explain 80% and 82% of total variances. These components are reflecting of the geogenic factor with superimposed pollution, the latter particularly pronounced in urbanized sections of the Langat river and dominant in downstream of the Kelantan river. There is no correlation between seasonal variations in major ion chemistry and environmental variables such as precipitation, discharge, temperature or solar activity.

Η παρούσα μελέτη αποσκοπεί στη διερεύνηση της σκηνικής προσέγγισης της αριστοφανικής κωμωδίας στο Εθνικό Θέατρο, καθώς επίσης και της κριτικής της πρόσληψής, μέσα από το παράδειγμα των Νεφελών. Η σκηνοθεσία των Νεφελών σε κλειστό χώρο το 1951 από τον Σωκράτη Καραντινό, σηματοδότησε την έναρξη των παραστάσεων της αττικής κωμωδίας στο Εθνικό Θέατρο της Ελλάδας. Ο Καραντινός, ο οποίος βασίσθηκε σε ιστορικές και αρχαιολογικές πηγές, προσπάθησε να εφαρμόσει τον αρχαίο τρόπο σκηνικής παρουσίασης. Ωστόσο από τις αρχαιοπρεπείς Νεφέλες του, έλειπε τελείως το κωμικό και το διονυσιακό στοιχείο του αριστοφανικού πνεύματος. Παρά τις αντικρουόμενες κριτικές η παράσταση του Καραντινού έθεσε τις βάσεις για έναν σοβαρό προβληματισμό πάνω στη σκηνική παρουσίαση της αττικής κωμωδίας στο Εθνικό Θέατρο. Ο Αλέξης Σολομός (1970) προσπάθησε να «ζωντανέψει» τον Αριστοφάνη εφαρμόζοντας τις αρχές που διατύπωσε στην πραγματεία του: «Ο ζωντανός Αριστοφάνης». Σύμφωνα με τον Σολομό η αρχαία κωμωδία έχει συγγένειες με σύγχρονες μορφές κωμωδίας, όπως είναι τα διάφορα νούμερα της επιθεώρησης, του τσίρκου, του μιούζικ χολ. Υιοθετώντας αυτές τις σκηνικές φόρμες κατάφερε να κάνει τον Αριστοφάνη προσιτό στο ευρύ κοινό, ιδιαίτερα στο φεστιβάλ της Επιδαύρου και των Αθηνών. O Κώστας Μπάκας με την έλευσή του στο Εθνικό Θέατρο, κόμισε εκεί την αριστοφανική σκηνική προσέγγιση του δασκάλου του Κάρολου Κουν, ο οποίος κινήθηκε στο πλαίσιο της «ελληνικότητας» και του «ελληνικού λαϊκού εξπρεσιονισμού». Τόσο ο Κοραής Δαμάτης, (1994) όσο και ο Γιάννης Ιορδανίδης (2001), παρόλο που χρησιμοποίησαν στοιχεία από τις δύο ερμηνευτικές σχολές (ηθοποιούς που εκπαιδεύτηκαν στο Θέατρο Τέχνης, τη θεαματικότητα του Σολομού με τους πολυπληθείς χορούς, τους αναγνωρισμένους συνθέτες και τους δημοφιλείς ηθοποιούς) προσπάθησαν να διαφοροποιηθούν από αυτές, χρησιμοποιώντας κάποια νεωτερικά στοιχεία που αφορούσαν κυρίως στη μουσική, τα σκηνικά, τα κοστούμια και τη μουσική. Πρέπει να σημειωθεί ότι ο Ιορδανίδης στις Νεφέλες του, εφάρμοσε την πρακτική της «νεοελληνικής αναλογίας», την αντικατάσταση δηλαδή των αγνώστων προσώπων, πραγμάτων, γεγονότων κλπ. της αριστοφανικής κωμωδίας, από ανάλογα γνωστά της σύγχρονης νεοελληνικής ζωής, ιστορίας, τέχνης, παράδοσης κλπ. / This study aims to explore the staging approach to Aristophanic comedy at the National Theatre, as well as its critical reception, through the example of The Clouds. The 1951 indoor direction of The Clouds by Sokrates Karantinos marked the outset of the performances of Attic comedy at the Greek National Theater. Karantinos, based on historical and archaeological sources, tried to apply the ancient way of staging. However, his archaic Clouds lacked completely the comic and the Dionysiac element of the Aristophanic spirit. Despite its controversial reviews, Karantinos’ performance laid the foundation for a serious questioning over the staging of Attic comedy at the National Theater. Alexis Solomos (1970) tried to “revive” Aristophanes applying the principles he put forward in his treatise: “The living Aristophanes.” According to Solomos the ancient comedy has affinities with modern forms of comedy such as the various numbers of the revue, the circus and the music hall. Adopting these stage forms he managed to make Aristophanes accessible to the general public, especially at the Epidaurus and Athens Festivals. Kostas Bakas with his advent at The National Theater in 1984, he brought there the Aristophanic stage approach of his teacher Karolos Koun, who moved into the frame of “Hellenism” and “Greek Folk Expressionism.” Both, Korais Damates (1994) and Yannis Iordanides (2001) although they used some elements of the two interpretative schools of Attic comedy (actors trained at the Art Theatre, the pageantry of Solomos with the numerous choruses, acknowledged composers and popular protagonists ) they tried to differentiate from them, using various innovative elements concerning mainly the sets, the costumes and the music. It should be noted that Iordanides in his Clouds applied the practice of the “Modern Greek analogy” which is the replacing of the unknown persons, things, facts etc. of the ancient comedy by analogous known ones from the Modern Greek life, history, art, tradition etc.

When a Time-of-Flight (ToF) depth camera is used to monitor a region of interest, it has to be mounted correctly and have information regarding its position. Manual configuration currently require managing captured 3D ToF data in a 2D environment, which limits the user and might give rise to errors due to misinterpretation of the data. This thesis investigates if a real time 3D reconstruction mesh from a Microsoft HoloLens can be used as a target for point cloud registration using the ToF data, thus configuring the camera autonomously. Three registration algorithms, Fast Global Registration (FGR), Joint Registration Multiple Point Clouds (JR-MPC) and Prerejective RANSAC, were evaluated for this purpose. It was concluded that despite using different sensors it is possible to perform accurate registration. Also, it was shown that the registration can be done accurately within a reasonable time, compared with the inherent time to perform 3D reconstruction on the Hololens. All algorithms could solve the problem, but it was concluded that FGR provided the most satisfying results, though requiring several constraints on the data.

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.