The research presented in this dissertation is on the development of advanced reduced rank adaptive signal processing for airborne radar space-time adaptive processing (STAP) and steering vector mismatch robustness. This is an important area of research in the field of airborne radar signal processing since practical STAP algorithms should be robust against various kinds of mismatch errors. The clutter return in an airborne radar has widely spread Doppler frequencies; therefore STAP, a two-dimensional adaptive filtering algorithm is required for effective clutter and jamming cancellation. Real-world effects in nonhomogeneous environments increase the number of adaptive degrees of freedom required to adequately suppress interference. The increasing computational complexity and the need to estimate the interference from a limited sample support make full rank STAP impractical. The research presented here shows that the reduced rank multistage Wiener filter (MWF) provides significant subspace compression better than any previous techniques in a nonhomogeneous environment. In addition, the impact of steering vector mismatch will also be examined on the MWF. In an airborne radar environment, it is well known that calibration errors and steering vector mismatch can seriously degrade adaptive array performance and result in signal cancellation. These errors can be caused by many non-ideal factors such as beam steering angle errors, multipath propagation, and phase errors due to array imperfections. Since the MWF centrally features the steering vector on its formulation, it is important to assess the impact of steering vector mismatch. In this dissertation, several novel techniques for increasing robustness are examined and applied to the MWF. These include derivative constraints, quiescent pattern control (QPC) techniques, and covariance matrix tapers (CMT). This research illustrates that a combination of CMT and QPC, denoted CMTQ, is very effective at mitigating the impact of steering vector mismatch. Use of CMTQ augmentation provides the steering vector mismatch robustness that we desire while improving the reduced-rank and reduced sample characteristics of the MWF. Results using Monte Carlo simulations and experimental Multichannel Airborne Radar Measurements (MCARM) data confirm that the use of CMTQ gives superior performance to steering vector errors at a much reduced rank and sample support as compared to conventional techniques. / Ph. D.

Im Vergleich zum Rest der Erde erfährt die Arktis eine signifikant schnellere Klimaerwärmung, die unter dem Begriff Arktische Verstärkung bekannt ist und mit zahlreichen sich verstärkenden Prozessen und Mechanismen einhergeht. Wolken spielen aufgrund ihrer Mitwirkung in verschiedenen, gegensätzlichen Effekten eine zwiespältige und eine der unsichersten Rollen für die Veränderung des arktischen Klimasystems. Daher ist die Untersuchung arktischer Wolken und ihrer Effekte von essenzieller Bedeutung, um den arktischen Klimawandel besser zu verstehen und in Modellen repräsentieren zu können. Diese Arbeit quantifiziert den bodennahen Strahlungseffekt von Wolken (engl. cloud radiative effect, CRE) aus einer Kombination von flugzeuggetragenen Breitbandstrahlungsmessungen während tiefer Flugabschnitte unter meist bewölkten Bedingungen und Strahlungstransfersimulationen für wolkenlose Bedingungen. Die Flugzeugmessungen wurden über den gegensätzlichen offenen Ozean- und Meereisoberflächen während dreier jahreszeitlich unterschiedlicher Kampagnen in der Umgebung von Spitzbergen aufgenommen. Ziel dieser Arbeit ist die Untersuchung des Einflusses von Oberflächen-, Wolken- und thermodynamischen Eigenschaften sowie Sonnenzenitwinkel (SZW) auf Unterschiede des solaren, thermisch-infraroten (TIR) und gesamten (solar+TIR) CRE, in Bezug auf die verschiedenen Kampagnen und Oberflächentypen. Die Unterschiede des solaren CRE werden überwiegend vom Kontrast der Oberflächenalbedo und vom jahreszeitlich variierenden SZW angetrieben. Der stärkste Abkühlungseffekt wurde im Frühsommer festgestellt und die über offenem Ozean beobachtete Abkühlung war stärker als über Meereis (-259 W m-2 vs. -65 W m-2 im Frühsommer, -108 W m-2 vs. -17 W m-2 im Frühjahr). Außerdem beeinflussen von Wolken ausgelöste Veränderungen der Oberflächenalbedo den solaren CRE je nach SZW und Oberflächentyp. Der TIR CRE zeigte aufgrund der vorherrschenden opaken Wolken und einer Kompensierung von Effekten sich ändernder Temperatur und Feuchte nur schwache Veränderungen zwischen den Kampagnen und Oberflächentypen (etwa 75 W m-2). Daher wird die Variabilität des gesamten CRE von der Schwankung des solaren CRE bestimmt. Über offenem Ozean wurde ein Abkühlungseffekt während aller Kampagnen beobachtet, über Meereis konnte der solare Abkühlungs- den TIR Erwärmungseffekt hingegen nur im Frühsommer ausgleichen. Für die gesamte Region Framstraße resultiert ein mittäglicher erwärmender, neutraler und abkühlender Effekt in Frühjahr, Frühsommer und Spätsommer aus dem Jahresgang der Meereisbedeckung. Zusätzlich zur eher qualitativen Analyse der einzelnen Einflussfaktoren auf die Unterschiede des solaren CRE wird ein Ansatz zur quantitativen Bestimmung dieser Faktoren angeregt. Diese neue Methode basiert auf einer Fallstudie mit sich verändernden Wolken- und Oberflächeneigenschaften senkrecht zur Eiskante während eines Warmlufteinschubs. Trotz signifikant mangelnder Komplexität der dem Fall zugrundeliegenden Parametrisierung werden plausible relative Beiträge von 77 % und 23 % zum Unterschied des solaren CRE zwischen offenem Ozean und Meereis für Oberflächen- respektive Wolkeneigenschaften ermittelt.:Zusammenfassung Abstract 1 General Introduction 1.1 Arctic Amplification – The Accelerated Warming of the Arctic 1.2 Clouds in the Arctic Climate System 2 Definitions and Theory 2.1 Radiative Quantities 2.2 Radiative Energy Budget 2.3 Surface, Cloud, and Atmospheric Properties 3 Motivation and Objectives 3.1 Previous Research on Cloud Radiative Effect 3.2 Aims of the Thesis 4 Observations and Methods 4.1 Aircraft Measurements 4.1.1 Broadband Radiation Measurements 4.1.2 Complementary Observations 4.2 Radiative Transfer Simulations 4.3 Calculation of Cloud Radiative Effect 4.4 Retrieval of Surface Albedo in Cloud-Free Conditions 4.4.1 Sea Ice Albedo and Retrieval of Equivalent Liquid Water Path 4.4.2 Open Ocean Albedo 4.4.3 Albedo of Inhomogeneous Surfaces 4.5 Uncertainty Estimation 4.5.1 Broadband Radiation Measurements 4.5.2 Radiative Transfer Simulations 4.5.3 Cloud Radiative Effect 4.6 Overview of Employed Data sets from all Campaigns 5 Statistical Analysis of Surface Cloud Radiative Effect 5.1 Campaign Characteristics 5.1.1 Sea Ice Distribution and Solar Zenith Angle 5.1.2 Thermodynamic Profiles 5.1.3 Cloud Properties 5.2 Impact of Cloud-Induced Albedo Modification 5.2.1 Impact on Surface Albedo 5.2.2 Impact on Solar Cloud Radiative Effect 5.3 Impact of Flight Altitude 5.4 Observed Cloud Radiative Effect 5.4.1 Solar Cloud Radiative Effect 5.4.2 Thermal-Infrared Cloud Radiative Effect 5.4.3 Total Cloud Radiative Effect 6 Sensitivity of Solar Cloud Radiative Effect to Surface and Cloud Properties 6.1 Introduction of Case 6.1.1 Synoptic Situation 6.1.2 Surface and Cloud Characteristics 6.2 Contributions to Solar Cloud Radiative Effect 6.2.1 Relative Contributions along a Continuous Time Series 6.2.2 Relative Contributions between States 7 Conclusions and Outlook 7.1 Summary and Conclusions 7.2 Outlook A Appendix A.1 Uncertainty Estimation A.1.1 Broadband Radiation Measurements A.1.2 Radiative Transfer Simulations A.1.3 Cloud Radiative Effect List of Figures List of Tables List of Symbols and Acronyms Bibliography Acknowledgements Summary of the Dissertation List of Papers and Author’s Contribution Supervision Statement / Compared to the rest of the globe, the Arctic experiences a significantly more rapid climate warming, which is called Arctic amplification and linked to numerous intensifying processes and mechanisms. Due to their contribution to and modification of various counteracting effects, clouds play one of the most ambiguous and uncertain roles in the change of the Arctic climate system. Thus, the investigation of clouds and their effects in the Arctic is essential to better understand and represent the Arctic climate change. This thesis quantifies the near-surface cloud radiative effect (CRE), which is obtained from a combination of airborne broadband radiation measurements during low-level flight sections under mostly cloudy conditions and radiative transfer simulations for cloud-free conditions. The airborne measurements were acquired over the contrasting open ocean and sea ice surfaces during three seasonally distinct campaigns in the vicinity of Svalbard. The objective of this thesis is to analyze the impact of surface, cloud, and thermodynamic properties as well as solar zenith angle (SZA) on differences of the solar, thermal-infrared (TIR), and total (solar+TIR) CRE with respect to the particular campaigns and surface types. The difference of the solar CRE is found to be predominantly driven by the contrasting surface albedo and the seasonally varying SZA. The strongest solar cooling effect was detected in early summer and the cooling observed over open ocean was stronger compared to sea ice (-259 W m-2 vs. -65 W m-2 in early summer, -108 W m-2 vs. -17 W m-2 in spring). Additionally, modifications of the surface albedo induced by the cloud-related illumination changes affect the solar CRE depending on SZA and surface type. The TIR CRE varied only weakly between campaigns and surface types (around 75 W m-2) due to the predominant opaque clouds and a compensation effect of changing temperature and humidity. Consequently, the variability of the total CRE is driven by the solar CRE variation. While a total cooling effect was present over open ocean during all campaigns, the solar cooling could compensate the TIR warming effect over sea ice only during early summer. For the entire Fram Strait region, the seasonal cycle of the sea ice distribution results in a total warming, neutral, and cooling effect during solar noon in spring, early summer, and late summer. In addition to the rather qualitative analysis of the individual contributors to the CRE differences, an attempt to quantitatively disentangle the contributions is proposed. This new method is based on a case study with varying cloud and surface properties over the sea ice edge during a warm air intrusion. Although the underlying parameterization developed for the case significantly lacks complexity, plausible relative contributions of surface and cloud properties of about 77 % and 23 % to the solar CRE difference between sea ice and open ocean are retrieved.:Zusammenfassung Abstract 1 General Introduction 1.1 Arctic Amplification – The Accelerated Warming of the Arctic 1.2 Clouds in the Arctic Climate System 2 Definitions and Theory 2.1 Radiative Quantities 2.2 Radiative Energy Budget 2.3 Surface, Cloud, and Atmospheric Properties 3 Motivation and Objectives 3.1 Previous Research on Cloud Radiative Effect 3.2 Aims of the Thesis 4 Observations and Methods 4.1 Aircraft Measurements 4.1.1 Broadband Radiation Measurements 4.1.2 Complementary Observations 4.2 Radiative Transfer Simulations 4.3 Calculation of Cloud Radiative Effect 4.4 Retrieval of Surface Albedo in Cloud-Free Conditions 4.4.1 Sea Ice Albedo and Retrieval of Equivalent Liquid Water Path 4.4.2 Open Ocean Albedo 4.4.3 Albedo of Inhomogeneous Surfaces 4.5 Uncertainty Estimation 4.5.1 Broadband Radiation Measurements 4.5.2 Radiative Transfer Simulations 4.5.3 Cloud Radiative Effect 4.6 Overview of Employed Data sets from all Campaigns 5 Statistical Analysis of Surface Cloud Radiative Effect 5.1 Campaign Characteristics 5.1.1 Sea Ice Distribution and Solar Zenith Angle 5.1.2 Thermodynamic Profiles 5.1.3 Cloud Properties 5.2 Impact of Cloud-Induced Albedo Modification 5.2.1 Impact on Surface Albedo 5.2.2 Impact on Solar Cloud Radiative Effect 5.3 Impact of Flight Altitude 5.4 Observed Cloud Radiative Effect 5.4.1 Solar Cloud Radiative Effect 5.4.2 Thermal-Infrared Cloud Radiative Effect 5.4.3 Total Cloud Radiative Effect 6 Sensitivity of Solar Cloud Radiative Effect to Surface and Cloud Properties 6.1 Introduction of Case 6.1.1 Synoptic Situation 6.1.2 Surface and Cloud Characteristics 6.2 Contributions to Solar Cloud Radiative Effect 6.2.1 Relative Contributions along a Continuous Time Series 6.2.2 Relative Contributions between States 7 Conclusions and Outlook 7.1 Summary and Conclusions 7.2 Outlook A Appendix A.1 Uncertainty Estimation A.1.1 Broadband Radiation Measurements A.1.2 Radiative Transfer Simulations A.1.3 Cloud Radiative Effect List of Figures List of Tables List of Symbols and Acronyms Bibliography Acknowledgements Summary of the Dissertation List of Papers and Author’s Contribution Supervision Statement

Mixed-phase clouds (MPCs) are a key component of the Arctic climate system by contributing to surface warming. The representation of MPC processes in climate models is currently incomplete, leading to high uncertainties in the prediction of future climate change. One such MPC process is riming, which describes the freezing of liquid droplets on ice particles upon contact. The occurrence and drivers of riming are poorly understood, particularly in the Arctic. This dissertation aims at gaining a better understanding of riming in the Arctic and its influence on ice water variability in MPCs. A novel framework to consistently estimate physical and scattering properties of rimed ice particles is presented. Two methods for quantifying riming have been developed and applied to airborne cloud radar and in situ measurements. Spatial scales of ice clustering in Arctic MPCs and their relation to riming were analyzed and compared to mid-latitude MPCs. First, mass-size, cross-sectional area-size, and backscattering cross-section relations were developed as a function of the normalized rime mass M for simulated rimed aggregates. The proposed framework (“riming-dependent parameterization”) allows to consistently simulate scattering properties of rimed aggregated ice particles. For radar frequencies of 35.6 GHz and 94.0 GHz, the resulting biases are less than 1 dB assuming exponential particle size distributions when using the particle masses and scattering properties of the individual simulated particles as a reference. Further, two methods for quantifying ice particle riming are presented. The first method is based on an inverse Optimal Estimation algorithm to retrieve M from cloud radar and in situ measurements ('combined method'). The second method relies on in situ observations only, relating M to optical particle shape measurements ('in situ method'). The methods were applied to data obtained during the HALO-(AC)³ aircraft campaign, which took place west of Svalbard in spring 2022. Median M values of 0.024 and 0.021 (mean values of 0.035 and 0.033) were derived using the combined and in situ method, respectively. Compared to other temperatures, the least amount of riming occurred at − 15°C. Rimed particles were observed at low liquid water path conditions. Finally, the influence of riming on the spatial variability of ice water content (IWC) was investigated. The analysis of HALO-(AC)³ data was extended to data collected during the IMPACTS aircraft campaign, which focused on mid-latitude winter storms. Riming accounted for 66% and 63% of the total IWC during IMPACTS and HALO-(AC)³, respectively. Riming increased the probability of ice cluster occurrence at similar scales as liquid water content variability. In cold air outbreak MPCs observed during HALO-(AC)³, riming led to additional IWC clustering at spatial scales of 3-5 km, which could be lined to the presence of mesoscale updraft features. These results help to improve our understanding of riming and the link between riming and IWC variability, and can be used to evaluate and constrain models of MPCs.

The theory of Lagrangian Coherent Structures (LCS) enables prediction of material transport by turbulent winds, such as those observed in the Earth's Atmospheric Boundary Layer. In this dissertation, both theory and experimental methods are developed for utilizing small fixed-wing unmanned aircraft systems (UAS) in detecting these atmospheric coherent structures. The dissertation begins by presenting relevant literature on both LCS and airborne wind estimation. Because model-based wind estimation inherently depends on high quality models, a Flight Dynamic Model (FDM) suitable for a small fixed-wing aircraft in turbulent wind is derived in detail. In this presentation, some new theoretical concepts are introduced concerning the proper treatment of spatial wind gradients, and a critical review of existing theories is presented. To enable model-based wind estimation experiments, an experimental approach is detailed for identifying a FDM for a small UAS by combining existing computational aerodynamic and data-driven approaches. Additionally, a methodology for determining wind estimation error directly resulting from dynamic modeling choices is presented and demonstrated. Next, some model-based wind estimation results are presented utilizing the experimentally identified FDM, accompanied by a discussion of model fidelity concerns and other experimental issues. Finally, an algorithm for detecting LCS from a single circling fixed-wing UAS is developed and demonstrated in an Observing System Simulation Experiment. The dissertation concludes by summarizing these contributions and recommending future paths for continuing research. / Doctor of Philosophy / In a natural or man-made disaster, first responders depend on accurate predictions of where the wind might carry hazardous material. A mathematical theory of Lagrangian Coherent Structures (LCS) has shown promise in ocean environments to improve these predictions, and the theory is also applicable to atmospheric flows near the Earth’s surface. This dissertation presents both theoretical and experimental research efforts towards employing small fixed-wing unmanned aircraft systems (UAS) to detect coherent structures in the Atmospheric Boundary Layer (ABL). These UAS fit several “gaps” in available sensing technology: a small aircraft responds significantly to wind gusts, can be steered to regions of interest, and can be flown in dangerous environments without risking the pilot’s safety. A key focus of this dissertation is to improve the quality of airborne wind measurements provided by inexpensive UAS, specifically by leveraging mathematical models of the aircraft. The dissertation opens by presenting the motivation for this research and existing literature on the topics. Next, a detailed derivation of a suitable Flight Dynamic Model (FDM) for a fixed-wing aircraft in a turbulent wind field is presented. Special attention is paid to the theories for including aerodynamic effects of flying in non-uniform winds. In preparation for wind measurement experiments, a practical method for obtaining better quality FDMs is presented which combines theoretically based and data-driven approaches. A study into the wind-measurement error incurred solely by mathematical modeling is presented, focusing on simplified forms of the FDM which are common in aerospace engineering. Wind estimates which utilize our best available model are presented, accompanied by discussions of the model accuracy and additional wind measurement concerns. A method is developed to detect coherent structures from a circling UAS which is providing wind information, presumably via accurate model based estimation. The dissertation concludes by discussing these conclusions and directions for future research which have been identified during these pursuits.

Airborne laser profiling is used to estimate tropical forest basal area, volume, and biomass. A procedure is developed and tested to divorce the laser and ground data collection efforts. The procedure involves 1) the collection of airborne laser data over the area of interest; 2) the collection of ground data in areas of similar forest cover type (in most cases in the same study area, but not necessarily coincident with the laser transects); 3) computer simulation of the forest canopy based on spatial and forest mensuration data available from the ground survey; 4) development of regression relationships between laser and ground measurements based on the simulated forest canopy; and 5) the use of these regressions with the airborne laser data using simple random sampling or line intercept sampling techniques. Variants of this simulation procedure were tested using three distinct data sets acquired in and over the tropical forests of Costa Rica. On two of the three study sites, airborne laser estimates of basal area, volume, and biomass grossly misrepresented ground estimates of same. On the third study site, where the widest ground transect samples were acquired, airborne and ground estimates agree within 10%. Basal area, volume, and biomass prediction inaccuracies in the first two study areas are tied directly to disagreement between simulated laser estimates and their airborne measurements of average canopy height, height variability, and canopy density. A number of sampling issues were investigated in order to define a large area inventory procedure which utilizes airborne laser data in conjunction with a limited ground sampling effort divorced spatially and temporally from the airborne laser sampling phase. The following results were noted in the analyses of the three study areas. 1) Four ground transect segment lengths were considered: 25, 50, 75, and 100m. The 25m segment length introduces a level of variability which may severely degrade prediction accuracy in these Costa Rican primary tropical forests. This effect is more pronounced as transect width decreases. A minimum transect length which mitigates significant mean square errors by capturing a representative spatial sample of the primary tropical forest is on the order of 50m. 2) Gaps between airborne laser segments on the order of 15m mitigate the effects of spatial autocorrelation. 3) The decision to transform or not to transform the dependent variable (eg., biomass) is by far the most important factor of those considered in this experiment. The natural log transformation of the dependent variable increases prediction error, and error increases dramatically at the shorter segment lengths. The most accurate models are simple linear models with forced zero intercept and an untransformed dependent variable. 4) Results do not suggest any apparent, consistent advantage to the use of parametric or nonparametric regression techniques; either is appropriate. 5) General linear models are developed to predict basal area, volume, and biomass using airborne laser height metrics. Laser metrics include average canopy height, all pulses (h̅_a,), average canopy height, canopy hits (h̅_c), and the coefficients of variation of these terms (c_a and c_c). Coefficients of determination, where calculated for comparable models with intercepts, range from 0.4 to 0.6. 6) Line Intercept Sampling techniques may be used to estimate h̅_a, h̅_c, canopy profile area (p), canopy density (g), canopy area, and canopy volume directly using airborne laser data without the need to identify individual tree crowns in the airborne laser data. Efforts to extend these metrics to estimates of basal area, volume, or biomass by attempting to relate canopy area to basal area and canopy volume to merchantable woody volume or above-ground dry biomass were unsuccessful. 7) The assumption of canopy shape needed to develop the simulated airborne laser measurements has a significant impact on the accuracy of the basal area, volume, and biomass estimates. Estimates of volume or biomass developed assuming an elliptical crown, parabolic crown, and conical crown are respectively 5%, 12%, and 23% larger than estimates developed based on spherical cross-sectional assumptions. Based on this body of research, airborne laser and ground sampling procedures are proposed for use for reconnaissance level surveys of inaccessible, forested regions. / Ph. D.

This research used computational fluid dynamics (CFD) to examine the behavior of airborne droplets released during respiratory events. The CFD model utilizes an Eulerian-Lagrangian approach, with turbulence resolved using the Spalart-Allmaras detached eddy simulation. The first part investigates airborne transmission and how modifying saliva during a sneeze impacts this process. The study employs CFD to simulate these respiratory events in a ventilated room. It finds that larger droplets alone are insufficient for droplet settling due to secondary breakdown processes. Modifiers that increase the Ohnesorge number show resistance to aerosolization from secondary breakup, resulting in more droplets with high settling rates, reducing their likelihood of airborne transmission. Another effective modifier reduces saliva content. The second part of the research develops a linear algebraic function to represent the near-field dispersion of droplets formed during respiratory events. This model facilitates the examination of flow interaction among various sources in different environments without requiring computationally expensive CFD simulations. The final part of the research involves developing a numerical Wells curve considering droplet evaporation, buoyancy, turbulence, breakup, and collision. The study also examines the effect of relative humidity on airborne transmission, finding that higher relative humidity slows the evaporation rate, which typically promotes faster droplet settling. Overall, these findings offer promising strategies for preventing spread of airborne transmission, highlighting the potential of saliva modification and advanced modeling techniques in public health interventions.

As a special subset of ad hoc networks, airborne networks aim to provide efficient network access for airborne and ground assets in a tactical environment. Conventional ad hoc routing protocols face some difficulties in such networks. First, significant overhead may be generated due to the high node mobility and dramatic topology changes. Second, temporary link failure may abort the delivery of a packet in some intermediate router. In this thesis, we propose a cluster-based reactive routing protocol to alleviate these problems. Our solution takes advantage of mesh routers installed in unmanned aerial vehicles or aircraft capable of hovering, when such airborne assets are available. As those mesh points usually have relatively stable connections among themselves, they play the role of cluster heads, forming a hierarchical routing structure. A simple self-organizing rule is introduced in cluster management to limit the cluster control overhead and route discovery flooding. In addition, a disruption tolerant mechanism (DTM) is deployed in the routing protocol to increase resilience to temporary link or node failure. The DTM utilizes the location, bearing and speed information provided by each node and intelligently maintains a buffer of packets that cannot be immediately delivered. If a temporary link failure occurs in the intermediate router during delivery, the packet is then buffered in that router up to a maximum time-to-live. The DTM also keeps track of link changes and tries to deliver the message as soon as a new path toward the destination is found. If the buffered messages are about to time out and the destination is still unreachable, the DTM still makes an effort to deliver the packet to another router with higher probability of eventually reaching the destination. This thesis also presents an implementation of the proposed solution in the ns-2 network simulator. The conventional Ad hoc On-Demand Distance Vector (AODV) routing protocol is adopted as the base model in the implementation. A mesh router model is programmed with two wireless interfaces. One of the interfaces is utilized to exchange routing information and packets with cluster members; the other is used to communicate with other mesh routers. This model is then installed on top of the AODV routing protocol and forms the hierarchical routing structure. The traditional AODV messages, including RREQ, RREP and HELLO, and routing tables are modified to support additional location information. Finally, the DTM is programmed and added to the AODV buffer management. The objective of this research is to use a mesh structure and DTM to improve the reliability and performance of airborne networks. The metrics of throughput and routing overhead are taken into consideration. The simulation results demonstrate that the proposed solution satisfies our research objectives. It achieves better performance than the conventional AODV, but introduces little overhead. The mesh structure can effectively adapt to high mobility, dynamic topology and different routing capabilities. The DTM provides a sophisticated way to maintain the buffer and mitigates the impact of intermittent links. / Master of Science

This study makes important scientific contributions by improving remote sensing methods for collecting bathymetric data. It demonstrates an improved and novel approach to utilizing Sentinel-2 reflectance data to extract satellite-derived bathymetry (SDB), validated against data from airborne LiDAR bathymetry (ALB). The study looks at how well SDB works in several coastal areas of the United States. It uses the Normalized Difference Turbidity Index (NDTI) and Total Suspended Solids (TSS) to see how water quality affects the accuracy of SDB. The study also analyzes how unoccupied aerial systems (UAS) can be combined with echo sounder systems to derive bathymetric maps with a high level of accuracy. Overall, the study's advancements in methodology and technology provide a foundation for future research and applications in coastal management and environmental monitoring, significantly impacting the understanding and management of inland to coastal water bodies.

Eagles Overhead provides a critical history of US Air Force Forward Air Controllers and examines their role, status, and performance in the Air Force's history. It begins by examining the US's initial adoption of air power, and American participation in aerial combat during World War I and traces the FACs' contributions to every US Air Force air campaign from the Marne in 1918 to Mosul in 2017. However, since 2001 FACs' contributions have been sporadic. Eagles Overhead asks why, despite the critical importance of FACs, have they not been heavily used on US battlefields since 2001? It examines the Air Force FAC's theoretical, doctrinal, institutional, and historical frameworks in the first nine chapters to assess if the nature of air warfare has changed so significantly that the concept and utility of the FAC has been left behind. Or, has the FAC been neglected since 2001 because the Air Force dislikes the capability as it clouds the service's doctrinal preferences? From these examinations, Eagles Overhead draws conclusions about the potential future of Air Force FACs.

An Airborne Mobile Aerosol Lidar (AMALi) was constructed and built at Alfred-Wegener-Institute for Polar and Marine Research (AWI) in Potsdam, Germany for the lower tropospheric aerosol and cloud research under tough arctic conditions. The system was successfully used during two AWI airborne field campaigns, ASTAR 2004 and SVALEX 2005, performed in vicinity of Spitsbergen in the Arctic. The novel evaluation schemes, the Two-Stream Inversion and the Iterative Airborne Inversion, were applied to the obtained lidar data. Thereby, calculation of the particle extinction and backscatter coefficient profiles with corresponding lidar ratio profiles characteristic for the arctic air was possible. The comparison of these lidar results with the results of other in-situ and remote instrumentation (ground based Koldewey Aerosol Raman Lidar (KARL), sunphotometer, radiosounding, satellite imagery) allowed to provided clean contra polluted (Arctic Haze) characteristics of the arctic aerosols. Moreover, the data interpretation by means of the ECMWF Operational Analyses and small-scale dispersion model EULAG allowed studying the effects of the Spitsbergens orography on the aerosol load in the Planetary Boundary Layer. With respect to the cloud studies a new methodology of alternated remote AMALi measurements with the airborne in-situ cloud optical and microphysical parameters measurements was proved feasible for the low density mixed-phase cloud studies. An example of such approach during observation of the natural cloud seeding (feeder-seeder phenomenon) with ice crystals precipitating into the lower supercooled stratocumulus deck were discussed in terms of the lidar signal intensity profiles and corresponding depolarisation ratio profiles. For parts of the cloud system characterised by almost negligible multiple scattering the calculation of the particle backscatter coefficient profiles was possible using the lidar ratio information obtained from the in-situ measurements in ice-crystal cloud and water cloud. / Das Airborne Mobile Aerosol Lidar (AMALi) wurde am Alfred-Wegener-Institut für Polar- und Meeresforschung in Potsdam für die Untersuchung arktischer Aerosole und Wolken der unteren Troposphäre entwickelt und gebaut. Das AMALi wurde erfolgreich in zwei AWI Flugzeugmesskampagnen, der ASTAR 2004 und der SvalEx 2005, die in Spitzbergen in der Arktis durchgeführt wurden, eingesetzt. Zwei neue Lidar Datenauswertungsmethoden wurden implementiert: die Two-Stream Inversion und die Iterative Airborne Inversion. Damit erwies sich die Berechnung der Profile der Teilchen Rückstreu- und Extinktionskoeffizienten mit einem entsprechenden Lidar Verhältnis, das charakteristisch für arktische Luft ist, als möglich. Der Vergleich dieser Auswertungen mit den Resultaten, die mit verschiedenen Fernerkundungs- und In-situ Instrumenten gewonnen worden waren (stationäres Koldewey Aerosol Raman Lidar KARL, Sonnenphotometer, Radiosondierung und Satellitenbilder) ermöglichten die Interpretation der Lidar-Resultate und eine Charakterisierung sowohl der reinen als auch der verschmutzten Luft. Außerdem konnten die Lidardaten mit operationellen ECMWF Daten und dem kleinskaligen Dispersionsmodel EULAG verglichen werden. Dadurch konnte der Einfluss der Spitzbergener Orographie auf die Aerosolladung der Planetaren Grenzschicht untersucht werden. Für Wolkenmessungen wurde eine neue Methode der alternativen Fernerkundung mit dem AMALi und flugzeuggetragenen In-situ Messgeräten verwendet, um optische und mikrophysikalische Eigenschaften der Wolken zu bestimmen. Diese Methode wurde erfolgreich implementiert und auf Mixed-Phase Wolken geringer optischen Dicke angewendet. Ein Beispiel hier stellt das Besamen der Wolken (sogenannte Feeder-Seeder Effekt) dar, bei dem Eiskristalle in eine niedrige unterkühlte Stratokumulus fallen. Dabei konnten Lidarsignale, Intensitätsprofile und die Volumendepolarisation gemessen werden. Zusätzlich konnten in den weniger dichten Bereichen der Wolken, in denen Vielfachstreuung vernachlässigbar ist, auch Profile des Teilchen Rückstreukoeffizienten berechnet werden, wobei Lidarverhältnisse genommen wurden, die aus In-situ Messungen für Wasser- und Eiswolken ermittelt wurden.