In the semiarid Southwestern United States, prolonged drought conditions since the early 2000s have resulted in widespread declines of the vegetation productivity in this water-constrained ecosystem, as revealed by analyses of the Normalized Difference Vegetation Index (NDVI). However, the spatial pattern of the NDVI response to dry years is not uniform: a divergent response of NDVI to precipitation is observed between the low-lying desert and the high montane forests at elevations above 2,500 meter. Weanalyzed relationships between 15 years of Moderate Resolution Imaging Spectroradiometer (MODIS) NDVI and gridded climate data (PRISM) along elevation gradients at scales from regional to local. Our elevation-explicit analysis captures the transition from water-limited to temperature-limited ecosystems, with a sign-reversal in the correlation coefficient between precipitation and NDVI observed at about 2,500-3,000m altitude. Wesuggest warmer temperatures and less snow cover associated with drier years as explanations for high elevation gains in vegetation productivity during dry years.

Nonlinear dynamical systems theory has inspired a new set of useful tools to be applied in climate studies. In this work we presented specific examples where information has been gained by the application of methods from nonlinear dynamical systems theory. The main goal is to understand the relative importance of stochastic forcing versus deterministic coupling within the context of Coupled General Circulation Models. This work address this important subject by approaching this goal through the development of a hierarchy of models with increasing complexity that we assert contain the essential dynamics of ENSO. We examined the effect of noise in a low order model and found that it is not restricted to blurring the attractor trajectories in phase space, but includes important changes in the dynamics of the system. The main results indicate that the presence of noise in a nonlinear system has two different effects. The presence of noise acts to increase the maximum Lyapunov exponent and can result in noise induced chaos if the system was originally stable. However, the same arguments are not valid if the original system is already in the chaotic regime, where the noise inclusion acts to decrease the maximum Lyapunov exponent, therefore increasing the system stability. The system of interest includes coupled ocean-atmosphere interactions and here we mimic this interaction by coupling two low order models with very different dominant time scales. These subsystems interact in a complex, nonlinear way and the behavior of the whole system cannot be explained by a linear summation of dynamics of the system parts. We used information theory concepts to detect the influence of the slow system dynamics in synchronizing the fast system in coupled models. We introduced a fast-slow coupled system, where both the slowness of the ocean model and the intensity of the boundary forcing anomalies contribute to the asymmetry and phase locking of both subsystems. The mechanisms controlling the fast modelspread were uncovered revealing uncertainty dynamics depending on the location of ensemble members in the model’s phase space. As an intermediate step between low order models and CGCMs we study the effect of noise on an intermediate complexity model. The addition of gaussian noise to the Zebiak-Cane model in order to understand the effects of noise on its attractor led to a way of estimating the noise level based on the effects of noise on the correlation dimension curves. We investigate the intrinsic predictability of the coupled models used here, and the different time scales associated with fast and slow modes were detected using the Finite Size Lyapunov Exponents. We found new estimates for the prediction horizon of ENSO for the Zebiak-Cane model as well as for the NCAR CCSM3 model and observations. The whole analysis of observations and CCSM3 was possible after applying noise reduction techniques. We also improved our understanding of three different noise reduction techniques by comparing the Local Projective Noise Reduction, the Interactive Ensemble strategy, and a Random Interactive Ensemble applied to CCSM3. The main difference between these two noise reduction techniques is when the process is applied. The Local Projective Noise Reduction can be applied to both model and observations, and it is done a posteriori in phase space, therefore the trajectories to be adjusted already posses the physical mechanisms embedded in them. The Interactive Ensemble approach can only be applied to model simulations and has shown to be a very useful technique for noise reduction since its done a priori while the system evolves instead of a posteriori, besides the fact that it allows to retrieve the spatial distribution of the noise level in physical space.

South Asia, a land of contrasting landscapes, seasons and climates, is highly vulnerable to climate variability over intra-seasonal to decadal time scales. In winter, precipitation over the western parts of south Asia and fog over the Indo-Gangetic (IG) plains are the two major climatic features. During summer most of the region comes under the grip of monsoon. Winter precipitation over the north-western parts of South Asia is associated with eastwards propagating ‘western disturbances’ originating mostly from Mediterranean. Both observations and regional climate-model simulations show that the winter precipitation increases/decreases during the positive/negative phases of the North Atlantic Oscillation (NAO) and the warm/cold phase of the El Niño-Southern Oscillation (ENSO). During these phases, the intensification of western disturbances results from the effect of an enhanced trough visible at sea-level as well as at higher altitudes over central Asia. The inter-annual variability of fog is coupled over IG plains with a significant trend in the fog frequencies, both in observations and ERA-Interim reanalysis data. This increase shows two distinct regime shifts in 1990 and 1998 with respect to mean and variance, this in contrast to a gradual increase of the humidity over the region. The thermodynamic analysis of the intra-seasonal summer monsoon active phases (APs) over Pakistan revealed that a few days before AP, an upper-level warm anomaly appears over the northern Hindu Kush-Himalaya region and is reinforced by surface heating. The baroclinic height anomalies, with a low-level anticyclone located east of the warming, causes a moisture convergence, strong enough to overcome the preexisting stable atmospheric conditions. The extratropical dynamics also play an important role for the inter-annual variation of the South-Asian monsoon. It is found that the two leading modes between the upper-level circulation in the Atlantic/European region and monsoon rainfall are the Circumglobal Teleconnection (CGT) and the summer NAO. The positive phase of the CGT is related to a widespread increase of monsoon rainfall, and a positive summer NAO is related to a precipitation dipole with its positive anomaly over Pakistan. / At the time of the doctoral defense, the following paper was unpublished and had a status as follows: Paper 4: Submitted.

No description available.

Submitted by Fabio Sobreira Campos da Costa (fabio.sobreira@ufpe.br) on 2016-09-06T13:31:18Z No. of bitstreams: 2 license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) Dissertação.pdf: 10717536 bytes, checksum: 2dde555896b4171b8f684053b12d4cb8 (MD5) / Made available in DSpace on 2016-09-06T13:31:18Z (GMT). No. of bitstreams: 2 license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) Dissertação.pdf: 10717536 bytes, checksum: 2dde555896b4171b8f684053b12d4cb8 (MD5) Previous issue date: 2016-02-15 / CAPEs / O clima semiárido do Nordeste Brasileiro representa um desafio para o adequamento das atividades agropecuárias, pois a irregularidade das chuvas associada a um planejamento ineficiente gera vulnerabilidades socioambientais crônicas. Por esta razão, o presente estudo procurou investigar a relação entre a dinâmica climática e os manejos agrários no ambiente semiárido da Bacia Hidrográfica do Rio Taperoá, localizada no centro do estado da Paraíba. Objetivou-se, a partir das relações investigadas, fornecer ferramentas para o planejamento de políticas territoriais de convivência com clima semiárido. Em um primeiro momento, foi realizada uma análise dos centros de ação atmosféricos responsáveis pela escala primária de circulação e produtores dos tipos de tempo sobre a área de estudo. Também foram estudadas as interações da grande escala de circulação atmosférica com as características geográficas locais, responsáveis pelas diferenciações climáticas em escala secundária. Em uma segunda etapa do trabalho procurou-se relacionar dados de produção agropecuária aos de chuva. As correlações lineares de Pearson demonstraram fracas relações da precipitação com o número anual de cabeças de gado e relações mais fortes com dados anuais de produção das lavouras temporárias (milho e feijão), especialmente no setor oriental da bacia. Diante desse fato, foi investigado o suprimento de água das culturas agrícolas de milho e feijão através da relação entre os dados de evapotranspiração mensal dessas plantas e de precipitação. Como complemento a essa abordagem metodológica, a partir de balanços hídricos climáticos e dos cultivos, foi estimada a disponibilidade de água no solo e para cultivo de milho, feijão, Capim Buffel e palma. O milho e o feijão se mostram bastantes vulneráveis à variabilidade pluviométrica na bacia hidrográfica estudada, enquanto o Capim Buffel e palma se mostraram mais eficientes no aproveitamento da água disponível. Na terceira etapa do trabalho procurouse investigar as adaptações técnicas de duas fazendas, localizadas no alto curso Rio Taperoá, à sazonalidade da chuva durante os anos de 2013 e 2014. Apesar das dificuldades observadas, essas fazendas mantiveram-se produzindo em um período de seca intensa por utilizarem elementos biológicos adaptados, e por desenvolverem tecnologias de planejamento que possibilitaram melhor convívio com a variabilidade da chuva. Os resultados encontrados corroboram a necessidade de um planejamento agrário que considere o ritmo e dinâmica climática, sendo capaz de conservar e promover manejos da terra que valorizem os recursos socioambientais locais. / The Brazilian northeastern semi-arid climate poses a challenge to the adaptation of agricultural activities, as the irregularity of rainfall associated with an inefficient planning generates chronic social and environmental vulnerabilities. For this reason, the present study aimed to investigate the relationship between climate dynamics and agricultural managements in the semiarid environment of the river basin Taperoá, located in the center of the state of Paraíba. The objective was to provide tools for planning territorial policies of coexistence with semiarid climate based on the relations investigated. At first, was performed an analysis of the atmospheric action centers responsible for the primary scale circulation and producers of the types of weather over the area of study. The interactions between the large scale atmospheric circulation and local geographical features, responsible for climate differences at secondary level were also studied. In a second stage of the study, it was sought to relate agricultural production data to those of the rain. The Pearson’s linear correlations showed weak links between rainfall and the annual number of cattle and stronger relations with annual production data of temporary crops (corn and beans), especially in the eastern sector of the basin. Given this fact, the water supply of crops of maize and beans were investigated by relating the monthly data from these plants evapotranspiration and precipitation. As a complement to this methodological approach, the water availability in the soil and for the cultivation of maize, beans, Buffel grass and palm was estimated from climatic and crops water balance. Maize and beans were shown to be quite vulnerable to rainfall variability in the studied basin, while Buffel grass and palm were more efficient in the use of available water. In the third stage of the study, it was sought to investigate the technical adjustments of two farms located in the upper reaches of Rio Taperoá, to the rain seasonality during the years 2013 and 2014. Despite the difficulties encountered, these farms remained in producing during a period of intense drought because of using adapted biological elements and developing planning technologies that allowed better contact with the variability of the rain. The results corroborate the need for an agrarian planning that consider the pace and climate dynamics, being able to keep promoting land managements that the use of local environmental resources.

A pesquisa tem como objeto de investigação a percepção climática, inserido o conceito de clima caracterizado como o ritmo de atuação dos tipos de tempo, e o conforto térmico. Os estudos mais conhecidos em conforto térmico quantificam os efeitos físicos e fisiológicos da ambiência atmosférica nas pessoas, baseados em índices, deixando lacunas no conhecimento tanto da dinâmica do clima, na qual se inserem as variáveis ambientais, como na subjetividade do fenômeno para o entendimento dessa realidade. Considerando essa problemática, a presente pesquisa questiona a insuficiência dos referidos índices por um viés exclusivamente positivista para o entendimento da percepção climática e do conforto térmico, especialmente em climas quentes como o de Palmas, Tocantins. No intuito de conhecer as essências do clima e do conforto térmico enquanto fenômenos vividos, a tese tem como objetivo contribuir com o entendimento de tais temas de forma interdisciplinar, enfocando de modo complementar seus aspectos objetivos e subjetivos. Para isso, a metodologia adotada compreendeu quatro etapas: (1) a análise rítmica anual em dois anos-padrão selecionados, um de padrão confortável e um de padrão desconfortável, 1997 e 2013, respectivamente, em conjunção com o Discomfort Index (DIT), proposto por Thom (1959); (2) a análise rítmica episódica, abarcando três episódios entre os anos 2015 e 2016, em conjunção com os índices de conforto PET e UTCI, aplicada em área externa na cidade; (3) a avaliação quali-quantitativa de dados pessoais dos moradores sobre sua percepção térmica, coletados por meio de questionários durante estes mesmos episódios; (4) e a análise dos dados subjetivos utilizando aplicação empírica do método fenomenológico, com as orientações operacionais de Giorgi (2012a). A tese procurou fornecer algumas contribuições metodológicas principais: um enfoque interdisciplinar da análise rítmica do clima (e do microclima medido in loco) com os índices de conforto térmico; uma abordagem interrelacional entre as análises climáticas e a percepção das pessoas sobre o clima e o conforto térmico, envolvendo seus aspectos objetivos e subjetivos; e o uso inédito de uma abordagem fenomenológica nos campos da climatologia e do conforto térmico. A dinâmica climática em Palmas demonstrou que a cidade apresenta altas temperaturas em todo o ano, com dois períodos distintos, chuvoso e seco, apresentando maior desconforto térmico na transição do período seco para o período chuvoso. Além disso, verificou-se que a cidade vem apresentando ampliação do desconforto térmico ao longo do período analisado (1995–2014). A avaliação quali-quantitativa apontou que as variáveis ligadas à experiência térmica, aos aspectos físico-fisiológicos e à experiência afetiva influenciaram na maioria das vezes parcialmente na percepção do conforto térmico das pessoas. A estrutura essencial revelada na análise fenomenológica demonstrou que o clima é somente mais um elemento em um vasto conjunto de aspectos naturais, sociais, econômicos, culturais etc., que interferem no bem-estar e na qualidade de vida dos sujeitos, e no seu conforto térmico, o que reforça a necessidade de uma abordagem menos parcial da realidade complexa da percepção climática. / The research has as its aim to investigate the climate perception, introduced the concept of climate characterized as the rhythm of the performance of the types of weather and thermal comfort. The better known studies on thermal comfort quantify the physical and physiological effects of the atmospheric ambience on people, based on indices, leaving gaps on the knowledge both in the climate dynamics, in which the environmental variables are inserted and in the phenomenon subjectivity for the understanding of this reality. Considering that issue, the present research enquires the insufficiency of the referred indices via an exclusively positivist bias for the comprehension of the climate perception and the thermal comfort, especially in warm climates like the one of Palmas, Tocantins, Brazil. With the purpose of learning about the essences of the climate and thermal comfort as lived phenomena, the thesis aims to contribute with the mastery of those themes in an interdisciplinary way, focusing their objective and subjective aspects in a complementary manner. To accomplish that, the method used complied four phases: (1) the annual rhythmic analysis in two selected standard-years, one of comfortable standard and one of uncomfortable standard, 1997 and 2013, respectively, in conjunction with the Discomfort Index (DIT), proposed by Thom (1959); (2) the episodic rhythmic analysis, involving three episodes within the years 2015 and 2016, in conjunction with the PET and UTCI comfort indices, applied in outer area of the city; (3) the quali-quantitative evaluation of personal data of the residents about their thermal perception, collected through questionnaires during those same episodes; (4) and the analysis of the subjective data utilizing empiric application of the phenomenological method, with the operational orientations of Giorgi (2012a). The thesis sought to provide some main methodological contributions: an interdisciplinary approach of the climate rhythmic analysis (and the microclimate measured in loco) with the thermal comfort indices; a inter-relational approach between the climate analyses and the people’s perception on the climate and thermal comfort, comprising their objective and subjective aspects; and the unprecedented use of a phenomenological focus on the climatology and thermal comfort. The climate dynamics in Palmas demonstrated that the city renders high temperatures throughout the year, with two distinct periods, rainy and dry, presenting greater thermal discomfort in the transition from the dry season to the rainy one. Furthermore, it was verified that the city has been presenting an expansion of the thermal comfort along the analyzed period (1995–2014). The quali-quantitative assessment pointed out that the variables linked to the thermal experience, to the physical-physiological aspects and to the affective experience most of the time influenced partially on the people’s thermal comfort perception. The essential structure unveiled in the phenomenological analysis showed that the climate is only one more element in a vast assembly of natural, social, economic and cultural aspects, which interfere on the well-being and the quality of life of the subjects and on their thermal comfort, what enhances the need of a less partial approach of the complex reality of the climate perception.

Der technologische Fortschritt hat in jüngster Zeit zu einer großen Zahl von Zeitreihenmessdaten über komplexe dynamische Systeme wie das Klimasystem, das Gehirn oder das globale ökonomische System geführt. Beispielsweise treten im Klimasystem Prozesse wie El Nino-Southern Oscillation (ENSO) mit dem indischen Monsun auf komplexe Art und Weise durch Telekonnektionen und Rückkopplungen in Wechselwirkung miteinander. Die Analyse der Messdaten zur Rekonstruktion der diesen Wechselwirkungen zugrunde liegenden kausalen Mechanismen ist eine Möglichkeit komplexe Systeme zu verstehen, insbesondere angesichts der unendlich-dimensionalen Komplexität der physikalischen Prozesse. Diese Dissertation verfolgt zwei Hauptfragen: (i) Wie können, ausgehend von multivariaten Zeitreihen, kausale Wechselwirkungen praktisch detektiert werden? (ii) Wie kann die Stärke kausaler Wechselwirkungen zwischen mehreren Prozessen in klar interpretierbarer Weise quantifiziert werden? Im ersten Teil der Arbeit werden die Theorie zur Detektion und Quantifikation nichtlinearer kausaler Wechselwirkungen (weiter-)entwickelt und wichtige Aspekte der Schätztheorie untersucht. Zur Quantifikation kausaler Wechselwirkungen wird ein physikalisch motivierter, informationstheoretischer Ansatz vorgeschlagen, umfangreich numerisch untersucht und durch analytische Resultate untermauert. Im zweiten Teil der Arbeit werden die entwickelten Methoden angewandt, um Hypothesen über kausale Wechselwirkungen in Klimadaten der vergangenen hundert Jahre zu testen und zu generieren. In einem zweiten, eher explorativen Schritt wird ein globaler Luftdruck-Datensatz analysiert, um wichtige treibende Prozesse in der Atmosphäre zu identifizieren. Abschließend wird aufgezeigt, wie die Quantifizierung von Wechselwirkungen Aufschluss über mögliche qualitative Veränderungen in der Klimadynamik (Kipppunkte) geben kann und wie kausal treibende Prozesse zur optimalen Vorhersage von Zeitreihen genutzt werden können. / Today''s scientific world produces a vastly growing and technology-driven abundance of time series data of such complex dynamical systems as the Earth''s climate, the brain, or the global economy. In the climate system multiple processes (e.g., El Nino-Southern Oscillation (ENSO) or the Indian Monsoon) interact in a complex, intertwined way involving teleconnections and feedback loops. Using the data to reconstruct the causal mechanisms underlying these interactions is one way to better understand such complex systems, especially given the infinite-dimensional complexity of the underlying physical equations. In this thesis, two main research questions are addressed: (i) How can general causal interactions be practically detected from multivariate time series? (ii) How can the strength of causal interactions between multiple processes be quantified in a well-interpretable way? In the first part of this thesis, the theory of detecting and quantifying general (linear and nonlinear) causal interactions is developed alongside with the important practical issues of estimation. To quantify causal interactions, a physically motivated, information-theoretic formalism is introduced. The formalism is extensively tested numerically and substantiated by rigorous mathematical results. In the second part of this thesis, the novel methods are applied to test and generate hypotheses on causal interactions in climate time series covering the 20th century up to the present. The results yield insights on an understanding of the Walker circulation and teleconnections of the ENSO system, for example with the Indian Monsoon. Further, in an exploratory way, a global surface pressure dataset is analyzed to identify key processes that drive and govern interactions in the global atmosphere. Finally, it is shown how quantifying interactions can be used to determine possible structural changes, termed tipping points, and as optimal predictors, here applied to the prediction of ENSO.

Khyber Pakhtunkhwa (31 ° 49'N, 70 ° 55'E bis 35 ° 50'N, 71 ° 47'E) liegt im Nordwesten Pakistans im Süden Asiens. Das Hindukusch-Gebirge in Afghanistan liegt im Westen, dem indischen Himalaya im Nordosten und die Karakorum Berge südlich vom tibetischen Hochland auf der Nordseite. Diese Arbeit besteht überwiegend aus drei separaten Studien entlang eines 200 km langen Transekts mit einem Höhengradienten ausgehend von den Sedimentbecken im Peshawar Tal (275 m ü.M.) bis hinauf zu den Malam Jabba Hills im Swat-Tal (2600 m ü.M.). Die erste Studie, die auf einer Datengrundlage von 160 Poaceae Arten beruht, zeigt Trends, dass polyploide C3- und C4-Poaceae-Arten größere Pollenkkörner als die jeweiligen diploiden Arten haben. In diesem Datensatz haben alle C4-Arten größere Pollenkörner als die C3-Arten. Ob Grassländer von C3 oder C4 Arten dominiert werden kann in verschiedenen Regionen und Lebensräumen durch die Untersuchung der Muster des Trends von zu- oder abnehmenden Pollenkorngrößen ermittelt werden. In unserem Datensatz ist Polyploidie bei C4-Gräsern häufiger als bei den C3 Arten. Die verwendete Methode kann auf Poaceae-Pollenkörner in Umweltarchiven angewendet werden, um das Klima der Vergangenheit zu rekonstruieren und die Dynamik der früheren Graslandökosysteme zu bewerten. Dieser Ansatz wird nicht nur bei laufenden paläoökologischen Studien helfen aufzuklären, wie die Änderungen der Vegetations-zusammensetzung und die Veränderungen in Biomen vergangener Graslandökosysteme zu entschlüsseln sind, sondern auch nützliche Erkenntnisse für die Vorhersage zukünftiger Entwicklungen ermöglichen. Die zweite Studie befasst sich mit modernen Pollenspektren aus Oberflächenproben und ihre Beziehung zu der umgebenden Vegetation, die nützliche Daten für die Interpretation von holozänen Pollenprofilen bietet. Dabei konnten entlang eines 200 km langen Höhengradienten vier verschiedene Höhenstufen unterschieden werden, wo die dominierenden Pflanzenfamilien, Poaceae, Asteraceae, Cyperaceae, Verbenaceae, Acanthaceae und Euphorbiaceae eine signifikante Korrelation mit dem gefunden Pollenniederschlag hatten, während sich bei anderen Familien, den Boraginaceae, Saxifragaceae, Apiaceae, Balsaminaceae und Rubiaceae große Unterschiede zu der zugehörigen Vegetationszusammensetzung ergaben. Für die Kalibrierung und Interpretation fossiler Pollendaten sollte also immer auch die aktuellen Beziehungen von Pollenniederschlag und Vegetationsdaten zumindest auf der Familienebene berücksichtigt werden. Die dritte Studie befasst sich mit einem Pollenprofil aus der Kabal Swat-Region, welches eine detaillierte Geschichte der Vegetation und des Klimas des Hindukuschs der letzten 3300 Jahre, also dem späten Holozäns enthält. Von 3300 bis 2400 cal BP, war eine subtropische semiaride krautige Vegetation hauptsächlich durch Cyperaceae- und Poaceae-Arten vertreten. Sie wurde ersetzt von gemischten Nadelwäldern mit Taxus, Pinus, sowie Juglans, Poaceae und Cyperaceae während der Zeit von 2400 bis 900 cal BP, was auf eine vergleichsweise moderate Klimaschwankung während des späten Holozäns weist. Der Rückgang der Poaceae von 2400 bis1500 cal BP und eine erneute Zunahme von 1500 bis 1200 cal BP Jahre zeigen, dass das Kabal Swat nass-kühlere und trocken-wärmere Phasen durchmachte. Nadelbäume in den gemischten Nadelwäldern treten heute bei größeren Höhe im alpinen Bereich auf. Weitere hochauflösende holozäne Pollenprofile des Hindukusch sind notwendig, um einen ausführlicheren Vergleich zu anderen süd- und zentralasiatischen Paläo-Archiven zu ermöglichen, die auch ein detaillierteres und anwendbares Wissen für Management und Naturschutzfragen ergeben.

Vom Standpunkt des Physikers aus gesehen, ist die Erde ein dynamisches System von großer Komplexität. Funktionale Netzwerke werden aus Beobachtungs-, und Modelldaten abgeleitet oder aufgrund theoretischer Überlegungen konstruiert. Indem sie statistische Zusammenhänge oder kausale Wirkbeziehungen zwischen der Dynamik gewisser Objekte, z.B. verschiedenen Sphären des Erdsystems, Prozessen oder lokalen Feldvariablen darstellen, bieten funktionale Netzwerke einen natürlichen Ansatz zur Bearbeitung fundamentaler Probleme der Erdsystemanalyse. Dazu gehören Fragen nach dominanten, dynamischen Mustern, Telekonnektionen und Rückkopplungsschleifen in der planetaren Maschinerie, sowie nach kritischen Elementen wie Schwellwerten, sogn. Flaschenhälsen und Schaltern im Erdsystem. Der erste Teil dieser Dissertation behandelt die Theorie komplexer Netzwerke und die netzwerkbasierte Zeitreihenanalyse. Die Beiträge zur Theorie komplexer Netzwerke beinhalten Maße und Modelle zur Analyse der Topologie (i) von Netzwerken wechselwirkender Netzwerke und (ii) Netzwerken mit ungleichen Knotengewichten, sowie (iii) eine analytische Theorie zur Beschreibung von räumlichen Netzwerken. Zur Zeitreihenanalyse werden (i) Rekurrenznetzwerke als eine theoretisch gut begründete, nichtlineare Methode zum Studium multivariater Zeitreihen vorgestellt. (ii) Gekoppelte Klimanetzwerke werden als ein exploratives Werkzeug der Datenanalyse zur quantitativen Charakterisierung der komplexen statistischen Interdependenzstruktur innerhalb und zwischen distinkten Feldern von Zeitreihen eingeführt. Im zweiten Teil der Arbeit werden Anwendungen zur Detektion von dynamischen Übergängen (Kipppunkten) in Zeitreihen, sowie zum Studium von Flaschenhälsen in der atmosphärischen Zirkulationsstruktur vorgestellt. Die Analyse von Paläoklimadaten deutet auf mögliche Zusammenhänge zwischen großskaligen Veränderungen der afrikanischen Klimadynamik während des Plio-Pleistozäns und Ereignissen in der Menschheitsevolution hin. / The Earth, as viewed from a physicist''s perspective, is a dynamical system of great complexity. Functional complex networks are inferred from observational data and model runs or constructed on the basis of theoretical considerations. Representing statistical interdependencies or causal interactions between objects (e.g., Earth system subdomains, processes, or local field variables), functional complex networks are conceptually well-suited for naturally addressing some of the fundamental questions of Earth system analysis concerning, among others, major dynamical patterns, teleconnections, and feedback loops in the planetary machinery, as well as critical elements such as thresholds, bottlenecks, and switches. The first part of this thesis concerns complex network theory and network-based time series analysis. Regarding complex network theory, the novel contributions include consistent frameworks for analyzing the topology of (i) general networks of interacting networks and (ii) networks with vertices of heterogeneously distributed weights, as well as (iii) an analytical theory for describing spatial networks. In the realm of time series analysis, (i) recurrence network analysis is put forward as a theoretically founded, nonlinear technique for the study of single, but possibly multivariate time series. (ii) Coupled climate networks are introduced as an exploratory tool of data analysis for quantitatively characterizing the intricate statistical interdependency structure within and between several fields of time series. The second part presents applications for detecting dynamical transitions (tipping points) in time series and studying bottlenecks in the atmosphere''s general circulation structure. The analysis of paleoclimate data reveals a possible influence of large-scale shifts in Plio-Pleistocene African climate variability on events in human evolution.

Do changes in how cross-equatorial energy transport is partitioned between the ocean and atmosphere impact the hemispheric climate response to forcing? To find out, we alter the cross-equatorial ocean heat transport in a state-of-the-art GCM and ascertain how changes in energy transport and its partitioning impact hemispheric climate and precipitation sensitivity following abrupt CO2-doubling. We further evaluate the applicability our results in CMIP6-class ESMs, where AMOC facilitates the northward cross-equatorial ocean heat transport. In our experiments, changes in ocean cross-equatorial energy transport trigger compensating changes in atmospheric energy transport through changes in the Hadley cells and a shift in the Intertropical Convergence Zone. However, the climate sensitivity in each hemisphere is linearly related to the ocean heat transport convergence, not atmospheric energy transport convergence, due to the impact of ocean heating on evaporation and atmospheric specific humidity. Similarly, we also find that ocean heat transport convergence controls the hemispheric precipitation sensitivity through the impact of ocean heating on surface evaporation. This relationship is also evident in CMIP6 models, where we find differences in hemispheric precipitation sensitivity to be related to the Atlantic Meridional Overturning Circulation (AMOC). Changes in the AMOC control hemispheric differences in upper ocean heat content, which then affect how the hydrologic cycle responds to CO2 forcing in each hemisphere. These results suggest that ocean dynamics impact the hemispheric climate response to CO2 forcing, particularly how much regional precipitation changes with warming. / Graduate