Abstract In northern regions such as Finland, snowpack represents a major water resource for aquatic and terrestrial ecosystems and different human uses, and snowmelt usually controls peak annual river discharge. To understand potential impacts of climate change, this thesis explored the effects of changes in surface air temperature (SAT) and precipitation patterns on snowpack accumulation and snowmelt processes in Finland. Two initial studies provided national and spatial pictures of long-term variability and changes in observed SAT and precipitation in Finland and their relationships with the atmospheric circulation patterns (ACPs) of the Northern Hemisphere (NH). On national scale, mean annual SAT and annual precipitation increased significantly in Finland during the past century. Seasonal analysis revealed increases in spring (MAM) and summer (JJA) SAT and in winter (DJF) and summer precipitation. SAT and precipitation were most significantly correlated with the Arctic Oscillation (AO), East Atlantic/West Russia (EA/WR), East Atlantic (EA) and Scandinavia (SCA) patterns. However, there were spatial differences within Finland as regards climate trends and relationships with ACPs. A study examining the dependence of snow resources on winter climate in Finland revealed a decline in snow water equivalent (SWE) and shortening of continuous snow cover duration (CSCD) in Finland during 1909-2008. This was mainly due to reductions in snowfall owing to winter warming and decreased precipitation in southern areas, but only to decreases in winter precipitation at higher latitudes. In southern Finland SWE and CSCD were associated with ACP affecting winter SAT (AO), and in central and northern parts with ACPs influencing winter precipitation (EA, EA/WR and AO). Analysis of snowmelt hydrology in Finland indicated that snowmelt flux has a much greater influence than rainfall on simulated peak snowpack outflow in Finland, which has decreased and shifted towards earlier in the year. / Tiivistelmä Pohjoisilla alueilla kuten Suomessa lumi edustaa merkittävää vesivarantoa mikä vaikuttaa vesi- ja maaekosysteemeihin sekä yhdyskuntien vesienkäyttöön. Lisäksi lumen sulanta aiheuttaa suurimmat vuosittaiset tulvahuiput. Tämä väitöstutkimus keskittyy ilmanlämpötilan ja sadannan muutoksien aiheuttamiin vaikutuksiin lumen kertymisessä ja lumen sulannan prosesseissa Suomessa, jotta ilmaston muutoksen aiheuttamia mahdollisia muutoksia voidaan paremmin ymmärtää. Väitöskirjan kaksi tutkimusta antavat kansallisen ja spatiaalisesti kattavan kuvan pitkäaikaisvaihtelusta ja muutoksista ilmanlämpötilassa ja sadannassa Suomessa ja niiden yhteyden ilmastojärjestelmiin (ACP) pohjoisella pallonpuoliskolla. Kansallisella tasolla, vuosittainen keski-ilmanlämpötila ja vuosisadanta lisääntyivät merkittävästä Suomessa viimeisen vuosisadan aikana. Kausittainen analyysi paljasti kevät ja kesä ilmanlämpötilojen sekä talvi ja kesä-sadantojen lisääntyneen. Ilmanlämpötila ja sadanta korreloi merkittävimmin Arktisen (AO), Itä Atlantti/Länsi Venäjä (EA/WR), Itä-Atlantti (EA) ja Skandinaavisen (SCA) oskillaatioiden kanssa. Eri puolilla Suomea tuloksissa oli spatiaalista eroa liittyen ilmasto trendeihin ja yhteyksiin ilmakehän kiertoliikkeisiin. Tässä tutkimuksessa selvitettiin lisäksi lumivarojen riippuvuutta talviajan ilmastosta Suomessa. Vuosien 1909-2008 aineiston perusteella lumenvesiarvossa (SWE) havaittiin laskua sekä pysyvän lumipeitteen kestossa (CSCD) lyhenemistä. Etelässä tämä todettiin pääosin olevan seurausta talviajan lumisateiden vähentymisestä, jota vuorostaan selitti ilman lämpeneminen ja kokonaissademäärän pienentyminen. Pohjoisilla leveysasteilla ainoastaan talviaikaisen kokonaissademäärän pienentyminen selitti vähentyneitä lumivaroja. Tutkimuksessa Etelä-Suomen aineiston osalta tulokset SWE ja CSCD:ssa voitiin yhdistää muutoksiin talviseen SAT:hen (AO) vaikuttavissa ilmastojärjestelmissä (ACP). Keski- ja pohjoisosissa Suomea ilmastojärjestelmät (EA, EA/WR ja AO) vaikuttivat ainoastaan talviaikaiseen sadantaan. Aineiston perusteella voitiin myös todeta, että Suomessa kevätaikaisesta lumensulannasta johtuvaan valuntahuippuun vaikuttaa enemmän välitön lumen sulanta kuin sulannan aikana esiintynyt vesisade. Lumen sulannan huippuarvo havaittiin myös laskeneen sekä sen ajoittuminen aikaistuneen.

>Magister Scientiae - MSc / Globally climate variability and anthropogenic effects are causing more perennial rivers to become non-perennial rivers. Non-perennial rivers are distinguished by their isolated pools which serve as refugia for aquatic organisms, water birds, and riparian vegetation. The literature on non-perennial rivers demonstrates that pools are poorly understood in terms of their location, nature, and geomorphic persistence. Therefore, this study examines the relationships between the spatial distribution, morphology, and substrate characteristics of pools in reaches of the Prins and Touws rivers in the Klein Karoo. A greater understanding of pools will facilitate better management, monitoring, and restoration strategies for pool ecology since the geomorphology of pools provides a key part of the ecological template. Worldview-2 satellite imagery (2017) and orthorectified aerial photography (2014, 2013, and 1944) were used to assess the effects of major flooding events on pools over time. A DGPS (Differential Global Positioning System) was used to survey the pool widths, lengths, depths, and valley widths, cross-sections, and longitudinal profiles of the river. Sediment samples and Wolman pebble counts were used to assess the grain size and organic matter content of each pool in the study area. Detailed descriptions of the characteristics of each pool in terms of position in the channel, valley form, and obstruction presence and type were also assessed. Results indicate that most of the large pools occur at bedrock outcrops of the valley margins, and smaller pools are associated with Vachellia karroo debris bar features. Larger and highly persistent pools are associated with valley confinement and smaller less persistent, scour pools occur mid-channel where the valley expands. Analysis of the results shows that the valley width is the dominant control on these forced pools. The type of obstruction also plays a role in the formation of the pool as large woody debris results in smaller pools whereas, bedrock outcrops result in larger sized pools. A significant relationship was found between the grain size and organic matter content of pools. Aerial photography of the spatial distribution of the pools revealed that before a major flood, the pools were small and patchy, whereas afterward, they were larger and more elongated. It is suggested that at the bedrock outcrops, major scouring and eddy processes drive the formation of larger pools during large flood events, whereas pool dissection by sediment deposits prevails during intervening intermediate to low flow periods. The results are discussed in terms of the geomorphic controls (valley width, pool dimensions, morphology, substrate, and obstruction characteristics) on the formation and maintenance of pools in dryland settings. A conceptual model is proposed to explain the geomorphic changes of the pools in the four geomorphological zones of non-perennial rivers.

Magister Artium - MA / Climate has been changing significantly around the globe; hence climate variability is of great interest to researchers. The changes in climate have caused variances in rainfall and temperature, both elements of paramount importance in farming, whether commercial or communal farming. As these fluctuations in temperature and rainfall occur, they cause direct impacts on different livelihoods, fauna and flora. The aim of this thesis is to investigate the human management responses of farmers in two different contexts of communal farming (Makolokwe) and commercial farming (Touws River valley), with a focus investigation on the adaptation and coping strategies of the farmers, as well as spatial analysis of the vegetation and rainfall variability. Farmers were asked to discuss climate and adaptation based on the rainfall data available as well as far as they could remember the occurrence of changes. Rainfall data was available between 1988 and 2017 for Touws River, while the data utilised for Makolokwe was available between 1928 and 2016. The link between the local knowledge of the farmers and scientific knowledge is an important aspect of this research. The Normalised Difference Vegetation Index (NDVI) was used to analyse the vegetation changes on a temporal and spatial scale in the context of Makolokwe and Touws River valley respectively. The differing variations in climate variability and change experienced by the two farming communities are placed alongside an exploration of the adaptation and coping measures which are put in place by farmers as a response to the changes evident in climate, as it allows for better and thorough understanding of the occurring changes in the two communities. The study found that perceptions about climate variability vary in the two communities although there are some common factors. Farmers’ perceptions about climate variability are drawn from their own observations at a local level as well as knowledge from the media regarding terms such as El Niño and drought. Farmers in both communities indicated that they experienced insufficient rain in the winter months which had an impact on the grazing areas and the management of the livestock. These months also threatened livelihoods, especially for farmers who depend on their livestock for their livelihood, in particular communal farmers. Perceptions of factors such as decreasing grazing and vegetation in their environments have led to the adoption of adaptation and coping strategies on the part of farmers. Commercial farmers have more choices in this regard than communal farmers, such as converting to game farming. Common coping strategies include: (1) farmers have had to subsidise and use alternative food sources for the livestock, (2) livestock numbers have been reduced in order to adapt to climate variability, with an impact on livelihoods (3) farmers have had to rely on their hope and faith that things will get better. Planning for climate variability is challenging for land managers. Knowledge and access to resources is therefore essential in ensuring that farmers are kept on track with the changing environment.

In this thesis, the role of soil water storage change on the annual water balance is evaluated based on observations at a large number of watersheds located in a spectrum of climate regions, and an annual water balance model is developed at the seasonal scale based on Budyko hypthesis. The annual water storage change is quantified based on water balance closure given the available data of precipitation, runoff, and evaporation estimated from remote sensing data and meteorology reanalysis. The responses of annual runoff, evaporation, and storage change to the interannual variability of precipitation and potential evaporation are then analyzed. Both runoff and evaporation sensitivities to potential evaporation are higher under energy-limited conditions, but storage change seems to be more sensitive to potential evaporation under the conditions in which water and energy are balanced. Runoff sensitivity to precipitation is higher under energylimited conditions; but both evaporation and storage change sensitivities to precipitation are higher under water-limited conditions. Therefore, under energy-limited conditions, most of precipitation variability is transferred to runoff variability; but under waterlimited conditions, most of precipitation variability is transferred to storage change and some of precipitation variability is transferred to evaporation variability. The main finding of this part is that evaporation variability will be overestimated by assuming negligible storage change in annual water balance, particularly under water-limited conditions. Budyko framework which expresses partitioning of water supply at the mean annual scale, is adapted to be applicable in modeling water cycle in short terms i.e., iv seasonal and interannual scales. Seasonal aridity index is defined as the ratio of seasonal potential evaporation and the difference between precipitation and storage change. The seasonal water balance is modeled by using a Budyko-type curve with horizontal shifts which leads prediction of seasonal and annual storage changes and evaporation if precipitation, potential evaporation, and runoff data are available.

Variabilidade climática é um sistema complexo gerado pela participação de diversos atores e sua atuação na dinâmica atmosférica, a (TSM) Temperatura da Superfície do Mar tem papel fundamental de influencia nas diversas características dos índices climáticos: Southern Hemisphere Anular Mode Index (SAM), Southern Oscillation Index (SOI), El Nino / Oscilação Sul (ENSO), (TNA) Tropical North Atlantic Index, (PDO) Pacific Decada Oscillation, North Atlantic Oscillation Index (NAO). Os Índices com variações climáticas e suas implicações, possuem um espectro de atuação e formação do clima, que se inicia nos macro-sistemas através de suas influências extraterrestres, pelos períodos de atividade solar e outros, que nos convidam a buscar um melhor entendimento sobre o clima e suas forças resultantes. Portanto essa é uma pesquisa simplista, procura demonstrar os entes envolvidos nos processos de variabilidade climática, realçando muito mais o papel dos oceanos e sua influencia de correlação sobre os regimes fluviométricos, estimando definir também a sua grande importância e um melhor entendimento do ciclo hidrológico da escala espaço-temporal na região da bacia Amazônica, partindo de uma leitura do sistema atmosférico e sua influencia dinâmica resultante sobre o ciclo hidrológico. A pesquisa adquiriu através da (ANA) Agencia Nacional de Águas os dados de vazão fluvial dos rios Solimões/Amazonas e Negro, e junto ao Earth System Research Laboratory Physical Sciences Division da NOAA, foram adquiridos os valores de TSM e Índices climáticos, já para os dados de precipitação foram solicitados junto Centro de Previsão de Tempo e Estudos Climáticos (CPTEC/INPE). Todos estes dados foram tratados em processamento no Software GrADS e ainda compilados em FORTRAN, para a analise estatística através de (R) Analise e Planejamento de Experimentos, para fornecer os dados de correlação linear, Test-t e regressão linear com o objetivo de sustentar e apoiar a analise dos resultados que possam prognosticar a partir da defasagem entre as variáveis TSM e o comportamento resultante da vazão fluvial. / Climate variability is a complex system generated by the participation of various actors and their role in atmospheric dynamics, the Sea Surface Temperature(SST) plays a key role in influencing the several features of the climate indexes: Southern Hemisphere Cancel Index Mode (SAM), Southern Oscillation Index (SOI), El Nino / Southern Oscillation (ENSO), (TNA) Tropical North Atlantic Index (PDO) Pacific Decade Oscillation, North Atlantic Oscillation Index (NAO). The climate changes indexes and their implications have a spectrum in the activity and formation of the climate, which begins in macro-systems through their extraterrestrial influences, during periods of solar activity and others, who urges us to search a better understanding of the climate and its resultant forces. Therefore, this is a simplistic research, seeking to show the entities involved in the climate variability processes, emphasizing much more the role of the oceans and its influence on the fluvial routines correlation, and estimating also define a major and also a better understanding of the hydrological cycle spatiotemporal scale in the region of the Amazon basin, starting from a reading of the atmospheric system and its resulting dynamic influence on the hydrological cycle, acquired through this research (ANA) National Water Agency data flow of the rivers Solimões / Amazonas and Negro River, and with the Earth System Research Laboratory - Physical Sciences Division of NOAA, which acquired values of SST and climate indexes. The precipitation data was requested from Center for Weather Forecasting and Climate Studies (CPTEC / INPE). All these data were processed in the processing software GrADS and also compiled in FORTRAN for statistical analysis using (R) - Analysis and Design of Experiments, to provide data for linear correlation, T-test and linear regression in order to sustain and support the analysis of the results which could predict from the discrepancy between the SST variables and the resulting conduct of river flow.

Les sécheresses des années 1970 accentuées dans les années 1980 et les aménagements hydroagricoles ont eu pour conséquence une certaine dégradation des ressources naturelles du delta intérieur du fleuve Niger (DIN). Cette dégradation des ressources naturelles associées à la pression croissante de la population sur le milieu a conduit à une gestion conflictuelle de ces ressources. De plus, le système d’exploitation actuel des ressources et le fonctionnement hydrologique font du DIN un écosystème complexe à gérer. Dans ces travaux, nous adoptons une approche intégrée et pluridisciplinaire pour aborder la problématique de gestion des ressources du DIN. L’approche mobilise l’hydrologie, la sociologie, l’agronomie et l’économie. L’analyse des données hydrologiques a permis de mettre en évidence une différence significative entre les dates de passage des maximums des fleuves Niger et Bani qui alimentent le DIN. Cette différence impacte les calendriers des principaux systèmes de production contribuant ainsi à exacerber les conflits. Les stratégies de gestion élaborées avec les parties prenantes, allient des pratiques de sécurisation et de maîtrise de l’eau, d’intensification, de régénération des ressources, de renforcement des capacités et des incitations économiques. Par ailleurs, dans un contexte de variabilité climatique accrue, nous avons analysé les perceptions d’un échantillon de pêcheurs, d’éleveurs et de cultivateurs sur la prévision du climat et sur l’intérêt des prévisions climatiques et des crues. Il ressort que les besoins en information climatique des usagers d’une plaine inondable comme le DIN se rapportent surtout aux dates de début de saison, de passage des maximums de crue, de la date d’arrivée des crues et des hauteurs maximales de crue. L’intérêt économique simulé de l’information climatique pour un système agraire de riziculture inondée présente un gain moyen de 10%. Par contre le coût des éventuelles erreurs de prévision serait particulièrement élevé pour les producteurs avec un déficit moyen sur le revenu de 24%. / The droughts of the 1970s intensified in the 1980s and the development of irrigation schemes upstream of the Inner Niger Delta in Mali (IND) have resulted in the degradation of natural resources. This degradation of natural resources associated with the increasing population pressure on the environment has led to a more conflictive management of these resources. In addition, the current operating system of resources and the hydrological functioning of the IND make the management of the ecosystem more complex.In this work, we adopt an integrated and multidisciplinary approach to address the IND resource management issues. The approach mobilizes hydrology, sociology, agronomy and economy.The analysis of hydrological data has highlighted a significant difference between the maximum passing dates of the two rivers that supply the IND. This difference impacts the schedules of the main production systems thus contributing to exacerbate conflict. The management strategies developed with stakeholders combine the practices of security and water control, intensification, resource regeneration, capacity building and economic incentives. Moreover, in a context of increased climate variability, we analyzed the perceptions of a sample of fishermen, herders and farmers on climate prediction and their interest of climate and flood forecasts.. It appears that the need for climate information of floodplain users as IND relate mainly to the onset date of rainy season, flood maximum passaging date, the arrival of floods and flood peak heights.The simulated economic value of climate information for an agrarian system of flooded rice obtains an average gain of 10%. As against the cost of possible prediction errors is particularly high for producers with an average deficit on income of 24%.

La thèse explore l’utilisation de modèles hydrologiques globaux pour estimer la disponibilité en eau agricole dans le contexte des Andes chiliennes semi-arides. Dans cette région, l’approvisionnement en eau des cultures irriguées de fonds de vallée durant l’été dépend de précipitations se produisant sous forme de neige à haute altitude lors de quelques évènements hivernaux. L’influence des phénomènes ENSO et PDO induit par ailleurs une forte variabilité climatique à l’échelle inter-annuelle, marquée par l’occurrence d’années extrêmement sèches ou humides. La région connaît aussi depuis les années 1980 une progression importante de la viticulture irriguée. Afin de prendre en compte les variations saisonnières et inter-annuelles de la disponibilité et de la consommation en eau d’irrigation, une chaîne de modélisation intégrée a été développée et différentes méthodes de quantification/réduction des incertitudes de simulation ont été mises en œuvre. Les écoulements naturels ont été simulés avec un modèle hydrologique global de type empirique/conceptuel prenant en compte les processus d’accumulation et d’ablation de la neige. En parallèle, les besoins en eau d’irrigation ont été estimés à l’échelle du bassin à partir de modèles phénologiques orientés processus et d’une approche simple du bilan hydrique du sol. Dans l’ensemble, une approche holistique et parcimonieuse a été privilégiée afin de maintenir un niveau d’abstraction mathématique et de représentation des processus équivalent à celui des modèles de bassin couramment utilisés. Afin d’améliorer l’utilité et la fiabilité des simulations obtenues en contexte de changement ou de forte variabilité climatique, l’effet des températures extrêmes sur le développement des cultures et l’impact des pertes en eau par sublimation à haute altitude ont fait l’objet d’une attention particulière. Ce cadre de modélisation conceptuel a été testé pour un bassin typique des Andes semi-arides (1512 km2, 820–5500 m a.s.l.) sur une période de 20 ans incluant une large gamme de conditions climatiques et des pratiques agricoles non-stationnaires (évolution des variétés de vigne, des surfaces et modes d’irrigation, etc). L’évaluation des modèles a été réalisée dans un cadre bayésien en faisant l’hypothèse d’erreurs auto-corrélées, hétéroscédastiques et non-gaussiennes. Différents critères et sources de données ont par ailleurs été mobilisés afin de vérifier l’efficacité et la cohérence interne de la chaîne de modélisation ainsi que la fiabilité statistique et la finesse des intervalles de confiance obtenus. De manière alternative, une caractérisation des erreurs de structure et de l’ambiguïté propre au choix du modèle hydrologique a été réalisée de manière non-probabiliste à partir d’une plate-forme de modélisation modulaire. Dans l’ensemble, la prise en compte explicite de la consommation en eau des cultures a mis en valeur certaines interactions entre paramètres hydrologiques et permis d’améliorer la fiabilité des simulations hydrologiques en année sèche. Finalement, une étude de sensibilité à différents seuils d’augmentation de la température et de la concentration en CO2 a été effectuée afin d’évaluer l’impact potentiel des changements climatiques sur le comportement de l’hydrosystème et la capacité à satisfaire la demande en eau d’irrigation dans le futur. / This thesis investigates the use of lumped catchment models to assess water availability for irrigation in the upland areas of northern-central Chile (30°S). Here, most of the annual water supply falls as snow in the high Cordillera during a few winter storms. Seasonal snowpacks serve as natural reservoirs, accumulating water during the winter and sustaining streams and aquifers during the summer, when irrigation demand in the cultivated valleys is at its peak. At the inter-annual timescale, the influence of ENSO and PDO phenomena result in the occurrence of extremely wet and dry years. Also, irrigated areas and grape growing have achieved a dramatic increase since the early 1980s. To evaluate the usefulness of explicitly accounting for changes in irrigation water-use in lumped catchment models, an integrated modeling framework was developed and different ways of quantifying/reducing model uncertainty were explored. Natural streamflow was simulated using an empirical hydrological model and a snowmelt routine. In parallel, seasonal and inter-annual variations in irrigation requirements were estimated using several process-based phenological models and a simple soil-water balance approach. Overall, this resulted in a low-dimensional, holistic approach based on the same level of mathematical abstraction and process representation as in most commonly-used catchment models. To improve model reliability and usefulness under varying or changing climate conditions, particular attention was paid to the effects of extreme temperatures on crop phenology and the contribution of sublimation losses to water balance at high elevations. This conceptual framework was tested in a typical semi-arid Andean catchment (1512 km2, 820–5500 m a.s.l.) over a 20–year simulation period encompassing a wide range of climate and water-use conditions (changes in grape varieties, irrigated areas, irrigation techniques). Model evaluation was performed from a Bayesian perspective assuming auto-correlated, heteroscedastic and non-gaussian residuals. Different criteria and data sources were used to verify model assumptions in terms of efficiency, internal consistency, statistical reliability and sharpness of the predictive uncertainty bands. Alternatively, a multiple-hypothesis and multi-criteria modeling framework was also developed to quantify the importance of model non-uniqueness and structural inadequacy from a non-probabilistic perspective. On the whole, incorporating the effects of irrigation water-use led to new interactions between the hydrological parameters of the modeling framework and improved reliability of streamflow predictions during low-flow periods. Finally, a sensitivity analysis to changes in climate conditions was conducted to evaluate the potential impacts of increasing temperatures and atmospheric CO2 on the hydrological behavior of the catchment and the capacity to meet future water demands.

Submitted by Sandra Pereira (srpereira@ufrrj.br) on 2016-10-25T11:21:37Z No. of bitstreams: 1 2016 - Juliana de Oliveira Tostes.pdf: 4618564 bytes, checksum: 951350c8676b3f82092fedfc3a9e0f79 (MD5) / Made available in DSpace on 2016-10-25T11:21:37Z (GMT). No. of bitstreams: 1 2016 - Juliana de Oliveira Tostes.pdf: 4618564 bytes, checksum: 951350c8676b3f82092fedfc3a9e0f79 (MD5) Previous issue date: 2016-02-29 / This research analyzes the temporal and spatial variables that can affect the distribution and frequency of hot spots in the state of Acre. Given the scarcity of regular spatial information and long time series for the study area, it was initially carried out a validation between air temperature and precipitation data in Global Grid Precipitation Climatology Centre (GPCC), University of Delaware (UDEL) and Global Historical Climatology Network (GHCN) with data from five Weather Stations Mainstream (EMC) to Acre and region, through an analysis of precision and accuracy of the data. Regarding precipitation, it was found that both the GPCC UDEL represented as the average variability significantly throughout the series. In relation to the air temperature standards, although the accuracy of GHCN and UDEL was low, it was satisfactory accuracy according to statistical methods. Assuming that the extreme weather events increase susceptibility to forest fires, then it was carried out an analysis of the influence of climate variability modes in generating categorized scenarios dry or wet years, based on the Standardized Precipitation Index (SPI) and Harmonic and Spectral (AHE). It was found that the AHE is not able to identify the intensity of the events, but was satisfactory in the signal cycles identifying the anomaly, i.e., whether the abnormality SPI was positive or negative. It was found that the Atlantic signal had greater influence on the precipitation of the Pacific. For the regions that correspond to Groups 1, 2 and 3 there was an inverse pattern for precipitation in relation to ENSO compared to the North and East Amazon. Thus, it identified negative precipitation anomalies during La Ni?a and El Ni?o events during positive events for the dry and rainy seasons. For the area corresponding to the effect Group 4 was otherwise. The natural climate variability patterns identified in this study may contribute to the establishment of strategies for prevention and adaptation to extreme events. Finally, in Chapter 3 was carried out an analysis of the spatial and temporal patterns of the fire in Acre, through a discussion of various climatic, environmental and anthropogenic variables that contribute to its occurrence. Thus, through the Random Forest algorithm were generated susceptibility maps that estimated the probability of fires and burned in the state. . It was found that although drought triggers an increase in the number of hot spots, its spatial pattern is more related to human factors such as the proximity areas already cleared. / A presente pesquisa analisa as vari?veis temporais e espaciais que podem afetar a distribui??o e frequ?ncia dos focos de calor no estado do Acre. Diante da escassez de dados regularmente espacializados e com longa s?rie temporal para a ?rea de estudo, inicialmente foi realizada uma valida??o entre os dados de temperatura do ar e precipita??o em grade do Global Precipitation Climatology Centre (GPCC), Universidade de Delaware (UDEL) e Global Historical Climatology Network (GHCN) com dados de cinco Esta??es Meteorol?gicas Convencionais (EMC) para o Acre e regi?o, atrav?s de uma an?lise da precis?o e exatid?o dos dados. Em rela??o ? precipita??o, verificou-se que tanto o GPCC quanto da UDEL representaram significativamente as variabilidades m?dias ao longo da s?rie. Em rela??o aos padr?es da temperatura do ar, embora a precis?o do GHCN e da UDEL tenha sido baixa, a exatid?o foi satisfat?ria segundo os m?todos estat?sticos. Partindo do pressuposto que os eventos clim?ticos extremos aumentam a suscetibilidade a inc?ndios florestais, em seguida foi realizada uma an?lise da influ?ncia dos modos de variabilidade clim?tica na gera??o de cen?rios categorizados de anos secos ou ?midos, baseado no ?ndice de Precipita??o Padronizado (SPI) e na An?lise Harm?nica e Espectral (AHE). Verificou-se que a AHE n?o foi capaz de identificar a intensidade dos eventos, mas mostrou-se satisfat?ria na identifica??o dos ciclos de sinal da anomalia, ou seja, se anomalia do SPI foi positiva ou negativa. Verificou-se que o sinal do Atl?ntico teve maior influ?ncia sobre a precipita??o do que o Pac?fico. Para as regi?es que correspondem os Grupos 1, 2 e 3 observou-se um padr?o inverso para a precipita??o em rela??o ao ENOS, quando comparado com a Amaz?nia Norte e Oriental. Assim, foram identificadas anomalias negativas de precipita??o durante eventos de La Ni?a e positivas durante eventos de El Ni?o para as esta??es seca e chuvosa. Para a regi?o que corresponde ao Grupo 4 o efeito foi contr?rio. Os padr?es de variabilidade natural do clima identificados nesse trabalho podem contribuir para o estabelecimento de estrat?gias de preven??o e adapta??o aos eventos extremos. Finalmente, no Cap?tulo 3 foi realizada uma an?lise sobre o padr?o espacial e temporal do fogo no Acre, atrav?s de uma discuss?o sobre diversas vari?veis clim?ticas, ambientais e antr?picas que contribuem para a sua ocorr?ncia. Assim, por meio do algoritmo Random Forest foram gerados mapas de suscetibilidade que estimaram a probabilidade de ocorr?ncia de inc?ndios e queimadas no estado. Verificou-se que, embora a estiagem propicie um aumento do n?mero de focos de calor, o seu padr?o espacial est? mais relacionado a fatores antr?picos, tais como a proximidade de ?reas j? desmatadas.

Unter atmosphärischen Zirkulationsregimen versteht man bevorzugte quasi-stationäre Zustände der atmosphärischen Zirkulation auf der planetaren Skala, die für eine bis mehrere Wochen persistieren können. Klimaänderungen, ob natürlich entstanden oder anthropogen verursacht, äußern sich in erster Linie durch Änderungen der Auftrittswahrscheinlichkeiten der natürlichen Regime. <br><br> In der vorliegenden Arbeit wurden dynamische Mechanismen des Regimeverhaltens und der dekadischen Klimavariabilität der Atmosphäre bei Abwesenheit zeitlich veränderlicher externer Einflussfaktoren untersucht. Das Hauptwerkzeug dafür war ein quasi-geostrophisches Dreischichtenmodell der winterlichen atmosphärischen Zirkulation auf der Nordhemisphäre, das eine spektrale T21-Auflösung, einen orographischen und einen zeitlich konstanten thermischen Antrieb mit nicht-zonalen Anteilen besitzt. Ein solches Modell vermag großskalige atmosphärische Strömungsvorgänge außerhalb der Tropen mit einiger Genauigkeit zu simulieren. Nicht berücksichtigt werden Feuchteprozesse, die Wechselwirkung der Atmosphäre mit anderen Teilen des Klimasystems sowie anthropogene Einflüsse. <br><br> Für das Dreischichtenmodell wurde ein automatisiertes, iteratives Verfahren zur Anpassung des thermischen Modellantriebs neu entwickelt. Jede Iteration des Verfahrens besteht aus einer Testintegration des Modells, ihrer Auswertung, dem Vergleich der Ergebnisse mit den NCEP-NCAR-Reanalysedaten aus den Wintermonaten Dezember, Januar und Februar sowie einer auf diesem Vergleich basierenden Antriebskorrektur. Nach Konvergenz des Verfahrens stimmt das Modell sowohl bezüglich des zonal gemittelten Klimazustandes als auch bezüglich der zeitgemittelten nicht-zonalen außertropischen diabatischen Erwärmung nahezu perfekt mit den wintergemittelten Reanalysedaten überein. <br><br> In einer 1000-jährigen Simulation wurden die beobachtete mittlere Zirkulation im Winter sowie ihre Variabilität realitätsnah reproduziert, insbesondere die Arktische Oszillation (AO) und ihre vertikale Ausdehnung. Der AO-Index des Modells weist deutliche dekadische Schwankungen auf, die allein durch die interne Modelldynamik bedingt sind. Darüber hinaus zeigt das Modell ein Regimeverhalten, das gut mit den Beobachtungsdaten übereintimmt. Es besitzt ein Regime, das in etwa der negativen Phase der Nordatlantischen Oszillation (NAO) entspricht und eines, das der positiven Phase der AO ähnelt. <br><br> Eine weit verbreitete Hypothese ist die näherungsweise Übereinstimmung zwischen Regimen und stationären Lösungen der Bewegungsgleichungen. In der vorliegenden Arbeit wurde diese Hypothese für das Dreischichtenmodell überprüft, mit negativem Resultat. Es wurden mittels eines Funktionalminimierungsverfahrens sechs verschiedene stationäre Zustände gefunden. Diese sind allesamt durch eine äußerst unrealistische Zirkulation gekennzeichnet und sind daher weit vom Modellattraktor entfernt. Fünf der sechs Zustände zeichnen sich durch einen extrem starken subtropischen Jet in der mittleren und obereren Modellschicht aus. <br><br> Da die Ursache des Regimeverhaltens des Dreischichtenmodells nach wie vor unklar war, wurde auf ein einfacheres Modell, nämlich ein barotropes Modell mit T21-Auflösung zurückgegriffen. Für die Anpassung des Oberflächenantriebs wurde eine modifizierte Form der iterativen Prozedur verwendet. Die zeitgemittelte Zirkulation des barotropen Modells stimmt sehr gut mit der zeitlich und vertikal gemittelten Zirkulation des Dreischichtenmodells überein. Das dominierende räumliche Muster der Variabilität besitzt eine AO-ähnliche Struktur. Zudem besitzt das barotrope Modell zwei Regime, die näherungsweise der positiven und negativen Phase der AO entsprechen und somit auch den Regimen des Dreischichtenmodells ähneln. Im Verlauf der Justierung des Oberflächenantriebs konnte beobachtet werden, dass die zwei Regime des barotropen Modells durch die Vereinigung zweier koexistierender Attraktoren entstanden. Der wahrscheinliche Mechanismus der Attraktorvereinigung ist eine Randkrise eines der beiden Attraktoren, gefolgt von einer explosiven Bifurkation des anderen Attraktors. <br><br> Es wird die Hypothese aufgestellt, dass der beim barotropen Modell vorgefundene Mechanismus der Regimeentstehung für atmosphärische Zirkulationsmodelle mit realitätsnahem Regimeverhalten Allgemeingültigkeit besitzt. Gestützt wird die Hypothese durch vier Experimente mit dem Dreischichtenmodell, bei denen jeweils der Parameter der Bodenreibung verringert und die Antriebsanpassung wiederholt wurde. Bei diesen Experimenten erhöhte sich die Persistenz und die Separiertheit der Regime bei abnehmender Reibung drastisch und damit auch der Anteil dekadischer Zeitskalen an der Variabilität. Die Zunahme der Persistenz der Regime ist charakteristisch für die Annäherung an eine inverse innere Krise, deren Existenz aber nicht nachgewiesen werden konnte. / Preferred quasi-stationary states of the planetary-scale atmospheric circulation, which may persist for one or several weeks, are referred to as atmospheric circulation regimes. Climate variations, either natural or anthropogenic, manifest themselves mainly in changes of the frequencies of occurrence of the natural regimes. <br><br> In the presented work, dynamical mechanisms of regime behavior and decadal climate variability of the atmosphere in absence of time-varying external forcing factors have been examined using a quasi-geostrophic three-level model of the wintertime atmospheric circulation over the northern hemisphere. This model has spectral T21 resolution, an orographic and a time-constant thermal forcing including non-zonal components. Such kind of a model is able to simulate large-scale extratropical atmospheric processes with reasonable accuracy. However, moisture processes, the interaction between the atmosphere and other parts of the climate system, and anthropogenic influences are not accounted for. <br><br> For the three-level model, a novel, automated, iterative procedure for the tuning of the thermal forcing has been developed. Every iteration of the procedure consists of a model test run, its evaluation, the comparison of the results with NCEP-NCAR reanalysis data for the winter months December, January, and February, and a forcing correction based on this comparison. After convergence of the procedure, the model matches the reanalysis data almost perfectly, as far as it concerns the zonal mean climate state and the time-mean non-zonal extratropical diabatic heating. <br><br> In a 1000-year simulation, the observed time-mean circulation in winter as well as its variability have been reproduced with considerable realism, in particular the Arctic Oscillation (AO) and its deep vertical extent. The modeled AO index exhibits pronounced decadal variations, exclusively caused by internal model dynamics. Furthermore, the model's regime behavior is in good agreement with observations. It possesses one regime resembling the negative phase of the North Atlantic Oscillation (NAO) and another resembling the positive phase of the AO. <br><br> A well-known hypothesis is the approximate correspondence between regimes and stationary solutions of the equations of motion. In the presented work, this hypothesis has been checked for the three-level model, but with negative result. Using a functional minimization method, six steady states have been found. All of them correspond to an extremely unrealistic circulation, and thus they are far away from the model's attractor. Five of the six steady states are characterized by a strongly exaggerated subtropical jet in the middle and upper model level. <br><br> As the origin of regime behavior was still unclear, a simpler model, namely a T21 barotropic model, has been reverted to. For the adaptation of the surface forcing, a modified version of the tuning procedure has been applied. The time-mean circulation of the barotropic model matches the temporally and vertically averaged circulation of the three-level model very well. The dominant spatial pattern of variability has an AO-like structure. Furthermore, the barotropic model possesses two regimes which approximately correspond to the positive and negative AO phase and therefore resemble the regimes of the three-level model. During the tuning of the surface forcing it has been observed that the two regimes of the barotropic model have emerged from the unification of two coexisting attractors. The mechanism responsible for this attractor merging is probably a boundary crisis of one of these attractors, followed by an explosive bifurcation of the other attractor. <br><br> It is hypothesized that the mechanism of regime genesis found in the barotropic model is universally valid for atmospheric circulation models with realistic regime behavior. This hypothesis is supported by four experiments with the three-level model, where the surface friction parameter has been decreased and the tuning procedure has been repeated, respectively. In these experiments, the persistence and separation of the regimes increases dramatically with decreasing friction, and thereby the fraction of decadal-scale variability. The increase of regime persistence is characteristic of approaching an inverse interior crisis, the existence of which, however, could not be proven.

<p>The Table Mountain Group (TMG) Formation is the lowest member of the Cape Supergroup which consists of sediments deposited from early Ordovician to early Carboniferous times, approximately between 500 and 340 million years ago. The Table Mountain Group (TMG) aquifer system is&nbsp / exposed along the west and south coasts of South Africa. It is a regional fractured rock aquifer that has become a major source of bulk water supply to&nbsp / meet the agricultural and urban water requirements of the Western and Eastern Cape Provinces of South Africa. The TMG aquifer system comprises of an approximately 4000 m thick sequence of quartz arenite and minor shale layers deposited in a shallow, but extensive, predominantly eastwest striking&nbsp / asin, changing to a northwest orientation at the west coast. The medium to coarse grain size and relative purity of some of the quartz arenites,&nbsp / together with their well indurated nature and fracturing due to folding and faulting in the fold belt, enhance both the quality of the groundwater and its&nbsp / exploitation potential for agricultural and domestic water supply purposes and its hot springs for recreation. The region is also home to some unique&nbsp / and indigenous floral species (fynbos) of worldwide importance. These and other groundwater dependent vegetation are found on the series of&nbsp / mountains, mountain slopes and valleys in the Cape Peninsula. The hydrogeology of the TMG consists of intermontane and coastal domains which&nbsp / have different properties but are interconnected. The former is characterized by direct recharge from rain and snow melt, deep groundwater circulation with hot springs and low conductivity groundwater. The coastal domain is characterized by shallow groundwater occurrence usually with moderate to&nbsp / poor quality, indirect recharge from rainfall of shallow circulation and where springs occur they are usually cold. The sustainable utilization of the TMG&nbsp / aquifer addressed the issues of the groundwater flow dynamics, recharge and discharge to and from the aquifer / challenges of climate change and climate variability and their potential impact on the aquifer system. The concept of safe yield, recharge and the capture principle and the integration of&nbsp / sustainable yield provided the basis for sustainable utilization with the adaptive management approach. Methodology used included the evaluation of&nbsp / recharge methods and estimates in the TMG aquifer and a GIS based water balance recharge estimation. The evaluation of natural discharges and&nbsp / artificial abstractions from the TMG aquifer system as well as its potential for future development. The Mann-Kendal trend analysis was used to test historical and present records of temperature and rainfall for significant trends as indication for climate variability and change. The determination of&nbsp / variability index of rainfall and standard precipitation index were additional analyses to investigate variability. The use of a case study from the Klein&nbsp / (Little) Karoo Rural Water Supply Scheme (KKRWSS) within the TMG study area was a test case to assess the sustainable utilization of TMG aquifers.&nbsp / Results show that recharge varies in time and space between 1% and 55% of MAP as a result of different hydrostratigraphic units of the TMG based on&nbsp / geology, hydrology, climate, soil, vegetation and landuse patterns however, the average recharge is from 1% to 5% of MAP. The TMG receives recharge&nbsp / mainly through its 37,000 km2 of outcrop largely exposed on mountainous terrain. Natural discharges from the TMG include 11 thermal and numerous&nbsp / cold spring discharges, baseflow to streams and reservoirs, and seepage to the ocean. Results from this study also show increasing temperature&nbsp / trend over the years while rainfall trend generally&nbsp / remain unchanged in the study area. Rainfall variability persists hence the potential for floodsand droughts in the region remain. Global and Regional Models predict about 10% to 25% reduction in rainfall and increase in variability in future. Impacts of&nbsp / his change in climate will affect the different types of aquifers in various ways. Increase in temperature and reduction in rainfall will increase&nbsp / evapotranspiration, reduce surface flows and eventually reduce shallow aquifer resources. Coastal aquifers risk upsurge in salinisation from sea level&nbsp / rise and increase in abstractions from dwindling surface water resources. While floods increase the risk of contamination to shallow aquifers droughts&nbsp / put pressure on all aquifers especially deep aquifers which are considered to be more reliable due to the fact that they are far removed from surface conditions. Future population growth and increase in freshwater demand will put more pressure on groundwater. Recharge to groundwater have been&nbsp / over-estimated in certain areas in the past leading to high abstraction rates from boreholes causing extensive groundwater storage depletion evident by high decline in groundwater levels in these areas and hampering sustainable management of the aquifer resources. Over-abstraction have resulted in&nbsp / loss of stream flow and baseflow reduction to streams during summer, complete loss of springs and reduction of flow to others. Flow to wetlands,&nbsp / riparian vegetation, and sometimes loss and shifts in dependent ecosystems have also resulted from over-abstraction. Sustainability has spatial and&nbsp / temporal implications due to changing climate and demand. The study recommends adaptive management practices in which several factors are&nbsp / considered in managing groundwater together with surface water resources in order to maintain ecological and environmental integrity. The KKRWSS&nbsp / and other groundwater supply schemes in the Western and Eastern Cape Provinces demonstrate the huge potential of the TMG to provide freshwatersupply for domestic and irrigation water needs however, the huge decline in groundwater levels due to over-abstraction in the KKRWSS and&nbsp / other groundwater schemes underscores the need for sustainable utilization of the TMG groundwater resources for present and future generations with&nbsp / minimal impacts on the quality, dependent hydrological and ecosystems as well as the environment.</p>