Simulations alternatively assuming a landscape with and without urbanization plus open-cast mining were performed with a non-hydrostatic model. lt is examined whether the atmospheric response to landuse changes is sensitive to the direction of the geostrophic wind. The results of simulations with the same geostrophic wind direction show that except for the cloud and precipitating particles the daily domain-averages of the variables of state hardly differ for the different landscapes. Nevertheless, the local weather may be affected appreciably over and downwind of the altered surfaces. The significant differences in the cloud and precipitating particles, however, are not bound to the environs of the landuse changes. Generally, the most significant differences occur for the cloud and precipitation particles, the soil wetness factors and the vertical component of the wind vector. The latter changes strongly influence the cloud and precipitation formation by the interaction cloud microphysics-dynamics. The results also indicate that for most of the quantities the local magnitude of the atmospheric response changes for the various directions of the geostrophic wind. However, the differences of the domain-averaged 24h-accumulated evapotranspiration are similar for all geostrophic wind directions. / Um zu untersuchen, ob die atmosphärische Antwort auf Landnutzungsänderungen sensitiv zur Richtung des geostrophischen Windes ist, wurden Simulationen durchgeführt, bei denen alternativ eine Landschaft mit und ohne Urbanisierung plus Tagebauten angenommen wurde. Die Simulationsergebnisse zeigen, daß - außer für Wolken- und Niederschlagspartikel - die täglichen Gebietsmittelwerte der Zustandsvariablen sich kaum für die beiden Landschaften unterscheiden. Trotzdem kann das lokale Wetter merklich über und im Lee der Oberflächen mit veränderter Landnutzung beeinflußt werden. Die signifikanten Differenzen in den Wolken- und Niederschlagspartikeln sind jedoch nicht an die unmittelbare Nähe der Landnutzungsänderungen gebunden. Generell treten die signifikanten Unterschiede bei den Wolkenund Niederschlagspartikeln, der Bodenfeuchte und der Vertikalkomponente des Windvektors auf. Letztere beeinflussen stark die Wolken- und Niederschlagsbildung durch die Wechselwirkung Wolkenmikrophysik-Dynamik. Die Ergebnisse zeigen außerdem, daß lokal der Grad der atmosphärischen Reaktion für die meisten Größen bei unterschiedlicher Richtung des geostrophischen Windes anders ausfällt. Die Differenzen der Gebietsmittelwerte der 24h-akkumulierten Evapotranspiration gleichen sich jedoch für alle Richtungen des geostrophischen Windes.

We present deep NH₃ and CCS maps of L1495-B218 filaments and the dense cores embedded within the filaments in Taurus. The L1495-B218 filaments form an interconnected, nearby, large complex extending over 8 pc. We observed the filaments in NH₃ (1,1)&(2,2), CCS Nⱼ = 1₂-0₁, and HC₇N J = 21-20 with spectral resolution of 0.038 km/s and spatial resolution of 31". The CSAR algorithm, which is a hybrid of seeded-watershed and binary dendrogram algorithm, identifies 39 leaves and 16 branches in NH₃ (1,1). Applying a virial analysis for the 39 NH₃ leaves, we find only 9 out of 39 leaves are gravitationally bound, and 12 out of 30 gravitationally unbound leaves are pressure-confined. Our analysis suggests that a dense core may form as a pressure-confined structure, evolve to a gravitationally bound core, and then undergo collapse to form a protostar. We find that the L1495A, B213E, and B216 regions have strong CCS emission and the B211 and B218 regions have weak CCS emission. Analysis of CCS emission with NH₃ (1,1) and dust continuum emission shows that CCS is not a good tracer for starless core evolution. On the other hand, CCS appears to trace recently accreted gas in L1495A and L1521D. We also present more realistic dynamic stability conditions for dense cores and filaments. In a new analysis of stability conditions we account for converging motions which have been modeled toward starless cores and take the effect of radiation fields. We find that the critical size of a dense core having a homologous converging motion with its peak speed being the sound speed is roughly half of the critical size of the Bonnor-Ebert sphere. We also find the critical mass/line density of a dense core/filament irradiated by radiation to be considerably smaller than that of the Bonnor-Ebert sphere/isothermal cylinder when the radiation pressure is stronger than the central gas pressure of dense core/isothermal cylinder. For regions in the inner Galaxy and near OB associations, the critical mass/line density of a dense structure may be less than 20% of the critical mass/line density of Bonnor-Ebert sphere/isothermal cylinder.

We present deep optical images of the Large and Small Magellanic Clouds (LMC and SMC) using a low cost telephoto lens with a wide field of view to explore stellar substructure in the outskirts of the stellar disk of the LMC (< 10 degrees from the LMC center). These data have higher resolution than existing star count maps, and highlight the existence of stellar arcs and multiple spiral arms in the northern periphery, with no comparable counterparts in the south. We compare these data to detailed simulations of the LMC disk outskirts, following interactions with its low mass companion, the SMC. We consider interaction in isolation and with the inclusion of the Milky Way tidal field. The simulations are used to assess the origin of the northern structures, including also the low density stellar arc recently identified in the Dark Energy Survey data by Mackey et al. at similar to 15 degrees. We conclude that repeated close interactions with the SMC are primarily responsible for the asymmetric stellar structures seen in the periphery of the LMC. The orientation and density of these arcs can be used to constrain the LMC's interaction history with and impact parameter of the SMC. More generally, we find that such asymmetric structures should be ubiquitous about pairs of dwarfs and can persist for 1-2 Gyr even after the secondary merges entirely with the primary. As such, the lack of a companion around a Magellanic Irregular does not disprove the hypothesis that their asymmetric structures are driven by dwarf-dwarf interactions.

The accomplished case studies focus on the influence of land-use on the distributions of latent heat-fluxes and cloud-water. The numerical case studies were performed with the threedimensional non-hydrostatic Mesoscale-Model GESIMA for different land-use distributions applying always the same initial conditions of a cloudy day in spring with a geostrophic wind of 8 m/s from the west. The cloud-water distributions at different times and at different levels, their temporal development, the daily sums of the domain-averaged latent heat-fluxes and cloud-water mixing ratios were investigated. Even simple initial conditions (no orography, stable atmosphere) and simple pattern in the land-use distributions emphasize that the influence of surface heterogeneity on meteorological processes cannot be neglected. As shown in this case study, land-use distribution influences the distribution and the amount of cloud-water as weil as the latent heat-flux. On the whole, all these processes are very complex and non-linear. / Die durchgeführten Sensitivitätsstudien konzentrieren sich auf den Einfluß der Landnutzungsverteilung auf die Flüsse latenter Wärme und das Wolkenwasser. Die numerischen Untersuchungen wurden mit dem dreidimensionalen nicht-hydrostatischen Mesoskalen-Modell GESIMA für verschiedene Landnutzungsmuster unter immer den gleichen meteorologischen Anfangsbedingungen für einen bewölkten Frühlingstag mit einem geostrophischen Wind von 8 m/s durchgeführt. Die Wolkenwasserverteilung zu bestimmten Zeiten und in bestimmten Niveaus, die zeitliche Entwicklung der Wolkenwasserverteilung, die Tagessummen der Gebietsmittelwerte der Flüsse latenter Wärme und des Wolkenwassers werden untersucht. Auch einfache Randbedingungen (keine Orographie, stabile, atmosphärische Bedingungen) und einfache Landnutzungsverteilungsmuster machen deutlich, daß der Einfluß der Heterogenität der Unterlage auf meteorologische Prozesse nicht zu vernachlässigen ist. Sie kann entscheidend die Verteilungen der Flüsse latenter Wärme und des Wolkenwassers beeinflussen. Die damit verbundenen Prozesse sind äußerst komplex und nicht linear.

No description available.

Os efeitos da interação entre aerossóis e nuvens foram estudados neste trabalho através da análise das propriedades ópticas de nuvens em função da profundidade óptica do aerossol (AOD). A região de trabalho foi a Amazônia, particularmente durante a estação seca e na transição entre a estação seca e a chuvosa, quando as queimadas lançam grande quantidade de partículas na atmosfera. Foram utilizados produtos derivados do MODIS (Moderate Resolution Imaging Spectroradiometer), sendo dois artigos utilizados como referência (Yu et al., 2007 e Koren et al., 2008). Observou-se comportamento de correlação entre fração de cobertura de nuvens e AOD conforme previsto em Koren et al. (2008) para outros anos estudados (2002 a 2008), nas estações seca e de transição entre seca e úmida, e em seis áreas menores de estudo de diferentes regiões da Amazônia, utilizando resultados das passagens da manhã (satélite Terra) e da tarde (satélite Aqua). Essas análises também foram realizadas restringindo-se os dados a situações atmosféricas semelhantes, conforme conteúdo de vapor dágua e instabilidade atmosférica, sendo observado o efeito microfísico através de médias, mas o radiativo não foi observado. / The effects of the interaction between aerosols and clouds are studied in this work by analyzing the optical properties of clouds as a function of the aerosol optical depth (AOD). The studied area is the Amazon region, particularly during the dry season and the transition between the dry to wet season, when fires release large amounts of particles in the atmosphere. MODIS (Moderate Resolution Imaging Spectroradiometer) products are used and two papers are used as reference (Yu et al., 2007 and Koren et al., 2008). As observed by Koren et al. (2008), correlation between cloud cover fraction and AOD was observed in this study, for a larger database, including years 2002 to 2008, both during the dry seasons and the transition between dry to wet. Six smaller areas in the Amazon were also investigated, using results from morning (Terra satellite) and afternoon (Aqua satellite) overpasses. These tests were also conducted by restricting the data according to atmospheric conditions such as water vapor content intervals and atmospheric instability. In this case, only the microphysical effect was observed, but not the radiative.

The Galactic center supermassive black hole (SMBH) Sagittarius A* (Sgr A*) is the closest such object and thus is an ideal target for investigation of galactic nuclei and their activity cycles. Its remarkable underluminous X-ray state is punctuated by outbursts on different time and energy scales. This thesis presents a study of past, current and possible future X-ray outburst activities from Sgr A*, using the hard X-ray telescope NuSTAR. Indication of substantial past Sgr A* activity, similar to that observed in low-luminosity active Galactic nuclei, has come from the Galactic center molecular clouds (GCMCs). Using these X-ray reflecting GCMCs, I have studied the characters of past Sgr A* X-ray outbursts. The current X-ray quiescence of Sgr A* is punctuated by directly detectable flares. The radiation mechanism and physical process of these X-ray flares are poorly understood. From about 1 Ms NuSTAR observations of Sgr A*, I collected nine bright X-ray flares. I studied their timing behavior and the correlation between flares' strengths and their spectra. Future Sgr A* X-ray activity could increase due to the infall of a gas cloud G2 into this SMBH. Finally, I present the Galactic center cosmic-ray population revealed by non-thermal X-ray filaments and its connection to Sgr A* outbursts.

Due to the wide range of physical scales involved, clouds cannot be fully resolved in models of the global climate, and so are parameterized. The resultant model deficiencies in simulating important cloud processes within the current climate are strongly implicated in the large uncertainty in model predictions of future climate changes. Previous work has highlighted the uncertainties in predictions of future climate related to thermodynamic cloud changes, understanding of which requires detailed observations of small-scale cloud microphysics. In this thesis, we argue that understanding the linkages between mid-latitude clouds and the general circulation of the atmosphere can advance efforts to constrain their response to climate forcing. We make this argument with three main methods of analysis: 1) observations, 2) state-of-the-art general circulation models, and 3) experiments with an idealized model of the global climate. First, we perform a comprehensive investigation of the observed inter-annual relationships between clouds, their radiative effects, and key indices of the large-scale atmospheric circulation. Using reanalysis data and satellite retrievals, we find a relationship between the edge of the Hadley circulation (HC) and the high cloud field that is largely robust against season and ocean basin. In contrast, shifts of the mid-latitude eddy-driven jet latitude, which had been the focus of previous work on the coupling between mid-latitude clouds and circulation, only correlate with the high cloud field in the wintertime North Atlantic. In that season and basin, poleward shifts of the circulation are associated with anomalous shortwave cloud radiative warming. During all seasons in the Southern Hemisphere, however, poleward shifts of the circulation are associated with anomalous shortwave cloud radiative cooling. Second, we examine Coupled Model Intercomparison Project phase 5 (CMIP5) model output to evaluate the models' simulation of the inter-annual co-variability between the Southern Hemisphere HC extent and the shortwave cloud radiative effect. In the control climate runs, during years when the HC edge is anomalously poleward, most models reduce their cloud cover in the lower mid-latitudes (approximately 30$^\circ$S - 45$^\circ$S) and allow more sunlight to warm the region, although we find no such shortwave radiative warming in observations. We correlate these biases in the co-variability between the HC extent and shortwave cloud radiative anomalies with model biases in the climatological HC extent. Models whose climatological HCs are unrealistically equatorward compared to the observations exhibit weaker climatological subsidence in the lower mid-latitudes and exhibit larger increases in subsidence there with poleward HC extent shifts than models with more realistic climatological HCs. This behavior, based on control climate variability, has important implications for the model response to forcing. In 4$\times$CO$_2$-forced runs, models with unrealistically equatorward HCs in the control climatology exhibit a stronger shortwave cloud radiative warming response in the lower mid-latitudes and tend to have larger values of equilibrium climate sensitivity than models with more realistic HCs in the control climatology. The above correlative analyses suggest that uncertainty in the linkages between mid-latitude clouds and the general circulation of the atmosphere contributes to uncertainty in the model response to forcing. Finally, we use simulations of the global climate in an idealized aquaplanet model to show that the biases in the climatological Southern Hemisphere circulation do indeed contribute to much of the model spread in the cloud-circulation coupling. We find that for the same 1$^\circ$ latitude poleward shift, simulations with narrower climatological HCs exhibit stronger mid-latitude shortwave cloud radiative warming anomalies than simulations with wider climatological HCs. The shortwave cloud radiative warming anomalies result predominantly from a subsidence warming of the planetary boundary layer, which decreases low-level cloud fraction and is stronger for narrower HCs because of a tighter mean meridional circulation. A comparison of the spread across aquaplanet simulations with that across CMIP5 models suggests that about half of the model uncertainty in the mid-latitude cloud-circulation coupling stems from this impact of the circulation on the large-scale temperature structure of the boundary layer, and thus can be removed by improving the representation of the climatological circulation in models. Therefore, a more realistic representation of the Hadley circulation in models can improve their representation of the linkage between mid-latitude clouds and the atmospheric circulation in the current climate and increase overall confidence in predictions of future climate.

Os efeitos da interação entre aerossóis e nuvens foram estudados neste trabalho através da análise das propriedades ópticas de nuvens em função da profundidade óptica do aerossol (AOD). A região de trabalho foi a Amazônia, particularmente durante a estação seca e na transição entre a estação seca e a chuvosa, quando as queimadas lançam grande quantidade de partículas na atmosfera. Foram utilizados produtos derivados do MODIS (Moderate Resolution Imaging Spectroradiometer), sendo dois artigos utilizados como referência (Yu et al., 2007 e Koren et al., 2008). Observou-se comportamento de correlação entre fração de cobertura de nuvens e AOD conforme previsto em Koren et al. (2008) para outros anos estudados (2002 a 2008), nas estações seca e de transição entre seca e úmida, e em seis áreas menores de estudo de diferentes regiões da Amazônia, utilizando resultados das passagens da manhã (satélite Terra) e da tarde (satélite Aqua). Essas análises também foram realizadas restringindo-se os dados a situações atmosféricas semelhantes, conforme conteúdo de vapor dágua e instabilidade atmosférica, sendo observado o efeito microfísico através de médias, mas o radiativo não foi observado. / The effects of the interaction between aerosols and clouds are studied in this work by analyzing the optical properties of clouds as a function of the aerosol optical depth (AOD). The studied area is the Amazon region, particularly during the dry season and the transition between the dry to wet season, when fires release large amounts of particles in the atmosphere. MODIS (Moderate Resolution Imaging Spectroradiometer) products are used and two papers are used as reference (Yu et al., 2007 and Koren et al., 2008). As observed by Koren et al. (2008), correlation between cloud cover fraction and AOD was observed in this study, for a larger database, including years 2002 to 2008, both during the dry seasons and the transition between dry to wet. Six smaller areas in the Amazon were also investigated, using results from morning (Terra satellite) and afternoon (Aqua satellite) overpasses. These tests were also conducted by restricting the data according to atmospheric conditions such as water vapor content intervals and atmospheric instability. In this case, only the microphysical effect was observed, but not the radiative.

Les principales caractéristiques des clouds d'infrastructure (laaS), comme l'élasticité instantanée et la mise à disposition automatique de ressources virtuelles, rendent ces clouds très dynamiques. Cette nature dynamique se traduit par de fréquents changements aux différents niveaux de l'infrastructure virtuelle. Étant données la criticité et parfois la confidentialité des informations traitées dans les infrastructures virtuelles des clients, la supervision de sécurité est une préoccupation importante pour les clients comme pour le fournisseur de cloud. Malheureusement, les changements dynamiques altèrent la capacité du système de supervision de sécurité à détecter avec succès les attaques ciblant les infrastructures virtuelles. Dans cette thèse, nous avons conçu un système de supervision de sécurité auto-adaptatif pour les clouds laaS. Ce système est conçu pour adapter ses composants en fonction des différents changements pouvant se produire dans une infrastructure de cloud. Notre système est instancié sous deux formes ciblant des équipements de sécurité différents : SAIDS, un système de détection d'intrusion réseau qui passe à l'échelle, et AL-SAFE, un firewall applicatif fondé sur l'introspection. Nous avons évalué notre prototype sous l'angle de la performance, du coût, et de la sécurité pour les clients comme pour le fournisseur. Nos résultats montrent que notre prototype impose un coût additionnel tolérable tout en fournissant une bonne qualité de détection. / Rapid elasticity and automatic provisioning of virtual resources are some of the main characteristics of laaS clouds. The dynamic nature of laaS clouds is translated to frequent changes that refer to different levels of the virtual infrastructure. Due to the critical and sometimes private information hosted in tenant virtual infrastructures, security monitoring is of great concern for both tenants and the provider. Unfortunately, the dynamic changes affect the ability of a security monitoring framework to successfully detect attacks that target cloud-hosted virtual infrastructures. In this thesis we have designed a self-adaptable security monitoring framework for laaS cloud environments that is designed to adapt its components based on different changes that occur in a virtual infrastructure. Our framework has two instantiations focused on different security devices: SAIDS, a scalable network intrusion detection system, and AL-SAFE, an introspection-based application-level firewall. We have evaluated our prototype focusing on performance, cost and security for both tenants and the provider. Our results demonstrate that our prototype imposes a tolerable overhead while providing accurate detection results.