Sur le bassin méditerranéen, les projections climatiques pour la fin du siècle indiquent un assèchement des étés accompagné d'une intensification des précipitations.Dans ce contexte, la caractérisation de la pluviométrie de la région est nécessaire pour appréhender son évolution future.Les modèles climatiques régionaux (RCM) sont des outils essentiels pour la compréhension du climat régional et pour la projection de son évolution.L'objectif de cette thèse est alors de caractériser et d'évaluer la pluie simulée par les RCM dans le sud-est de la France, typique des régions méditerranéennes côtières.La description de la pluie observée aux mêmes échelles que les RCM en est un préalable.La pluie observée et simulée est caractérisée en termes de valeurs et de structure spatiale et temporelle de l'occurrence et de l'intensité.Les liens entre ces caractéristiques et les processus physiques sous-jacents sont explorés grâce à une analyse par type de temps.Dans les modèles, le volume annuel total d'eau apporté par la pluie sur l'ensemble de la région d'étude est proche des valeurs observées.Ce volume n'est toutefois pas réparti également dans le temps et dans l'espace dans les observations et dans les simulations.Parmi les multiples caractéristiques de la pluie observée et simulée, cette étude souligne l'influence des forçages du relief et des processus liés au cycle diurne de l'énergie solaire à la fois sur le déclenchement et sur l'intensité des précipitations.Ainsi, la pluie se produit préférentiellement en fin d'après-midi, en lien avec le chauffage diurne de la surface.Cependant, dans les modèles, le maximum d'occurrence est plus précoce que dans les observations, ce qui suggère une réponse trop rapide du schéma de convection au cycle diurne des flux de surface, liée à l'absence de la phase de transition entre la convection peu profonde et la convection profonde dans la majorité des schémas.Par ailleurs, au sein du domaine d'étude, l'influence du relief sur les caractéristiques de la pluie est plus marquée pour les Cévennes que pour les Préalpes.Les RCM reproduisent cette influence du relief sur les caractéristiques de pluie.Toutefois, les contrastes entre plaines et reliefs sont plus accentués dans les modèles que dans les observations, notamment lorsque le forçage de grande échelle est faible et la convection dominante dans la région d'étude.L'accentuation du contraste entre plaine et montagne dans les modèles semble donc provenir d'une trop grande sensibilité des schémas de convection au relief qui favorise la convergence et l'instabilité de la masse d'air. / Climate projections for the end of the century indicate drier summers and more intense precipitation in the Mediterranean.In this respect, the characterization of rainfall in the region is necessary to understand its future changes.Regional climate models (RCM) are essential tools to understand the regional climate and to project its future evolution.This thesis aims at characterizing and evaluating rainfall simulated by RCM in Southeast France, typical of the mediterranean coastal regions.The description of observed rainfall at the same scales as RCM is a prerequisite.Observed and simulated rainfall is described in terms of values and spatial and temporal structure of occurrence and intensity.Weather types are used to explore the relation between rainfall features and the underlying physical processes.In the RCM, the annual total volume of water precipitated over the study region is closed to the observed values.However, this total volume is not distributed the same in space and time in the RCM simulations and in the observations.Among the multiple facets of the rainfall climatology, this study highlights the influence of the relief and of the solar cycle both in the triggering and in the intensity of rain.Rain appears to occur preferentially in the late afternoon, in connection with the daytime heating of the surface.However, the maximum of rain occurrence simulated by the RCM is earlier than in the observations, suggesting a too quick response of the convection scheme to the diurnal cycle of surface fluxes, in relation to the absence of transition between shallow and deep convection in most schemes.Besides, within the study region, the orographic forcing appears to be quite different for the two ranges of the domain and is much more pronounced over the Cévennes.The RCM reproduce the influence of the topography on rainfall features.Yet, the contrast between plains and mountains is more pronounced in the models than in the observations, especially when the large-scale forcing is weak and the convection is prevailing in the study area.The contrast accentuation between plain and relief in the models seems to be due to a too high sensitivity of the convection schemes to the air mass convergence and instability favored by the relief.

Made available in DSpace on 2014-08-20T14:25:52Z (GMT). No. of bitstreams: 1 dissertacao_gilson_carlos_da_silva.pdf: 6390842 bytes, checksum: 4ee553c938a05c41b76eeb4831643835 (MD5) Previous issue date: 2011-08-31 / The time-variation feature of extreme precipitation events (those can result in flooding) on east and north regions of the Santa Catarina State, one of the Brazilian regions most attained by damages owning to heavy rain episodes, is analyzed in this study. For this, it were selected some cities whose history of flooding based on many sources, as the Defesa Civil Estadual was employed to built a threshold to identify the precipitation events that can cause flooding. The observed precipitation data, from 1951 to 2010, from ANA (Agência Nacional de Águas) was used to the analysis of daily rainfall occurred until fifteen days before the flooding and for the counting of this type of event. The methodology employed to detect these events was based on mean thresholds following the rainfall observed on the selected cities. The counting of the occurrences generated the time-variation over such period, indicating positive and also some negative, although not significant tendencies on this region, and a significative linear correlation with global scale climate phenomena in some of the cities. It is also observed the seasonal behavior for the present time and for a future climate scenario, ranging from 2070 to 2100, which aim is to give information to a better planning of the cities, through the regional climate model HadRM3P, from Hadley Centre (UK), simulated and provided by CCST (Centro de Ciências do Sistema Terrestre) do INPE (Instituto Nacional de Pesquisas Espaciais), considering the A2 scenario (more pessimist) following IPCC (Intergovernmental Panel on Climate Change). In comparison against present climate, the estimated projection by climatic model shows an increasing of the frequency of these extreme precipitation events in all selected cities, for all seasons mainly in autumn. / Este estudo analisa o aspecto temporal dos eventos extremos de precipitação com potencial para causar inundação na região Leste e Norte do Estado de Santa Catarina, uma das regiões brasileiras que mais sofrem transtornos devido à chuva intensa. Foram selecionadas algumas cidades cujo histórico de inundação construído através de várias fontes, como a Defesa Civil Estadual foi usado para a confecção de um limiar para identificar tais eventos. Foram utilizados dados de precipitação da ANA (Agência Nacional de Águas) no período de 1951 a 2010, para análise da chuva diária ocorrida até quinze dias antes das inundações e para a quantificação dos eventos extremos de precipitação com potencial para provocar inundação. A metodologia empregada para detecção desses eventos foi a de limiares médios, baseada na análise pontual da precipitação nas cidades atingidas. A quantificação do número de eventos gerou a variação temporal no período, em que pode-se analisar as ocorrências de tendência positiva e também alguma negativa, embora não significativa na região, além de correlação linear significativa, em algumas cidades, com fenômenos climáticos de escala global. É examinado também o aspecto climatológico sazonal do presente e de um cenário climático para o final do século (2070-2100), cujo objetivo é fornecer informações para um melhor planejamento das cidades, usando dados do modelo climático regional HadRM3P, do Hadley Centre (UK), simulados e fornecidos pelo Centro de Ciências do Sistema Terrestre do Instituto Nacional de Pesquisas Espaciais (CCST/INPE), considerando o cenário A2 (mais pessimista) do IPCC (Painel Intergovernamental sobre Mudanças Climáticas). Na comparação com o clima presente, a projeção simulada pelo modelo climático indicou aumento da frequência de ocorrência dos eventos em todas as cidades, para todas as estações do ano, principalmente para o outono.

In the last 100 years, a rise in the global mean temperature has been noted, and projections show even higher temperatures in the future. The temperature rise can lead to changes in the weather patterns and therefore the thunderstorm activity in a future warmer climate has been investigated in this study. The future projections were made with an ensemble of 8 General Circulation Models downscaled with the regional climate model RCA4, developed at SMHI. Temperature and humidity data at four different levels in the atmosphere has been used to compute three different stability indices. Stability indices indicate potential for deep convection in the atmosphere, from which thunderstorms are developed. It was found that the projections show an increase in thunderstorm potential in a warmer future climate. In Sweden, the projections show an increase with about 15 more days with risk of thunderstorms at the end of the 21st century for the RCP4.5 scenario, corresponding to an increase of 40% in the south, and an even larger increase in the north. For the RCP 8.5 scenario, the projected change in days with risk of thunderstorms corresponds to an increase about 20 days, or about 60% more thunderstorm days in south of Sweden. In other parts of Europe, the increase is expected to be even larger, mainly in the mountain regions. It was also found that the thunderstorm season is projected to be extended in the future, with more days with risk of thunder in May and September. The increase in number of days with risk of thunderstorms is a result of the greater amount of water vapour that the atmosphere is able to hold in a warmer climate. Even if thunderstorms are projected to increase, other factors counteract, such as a decrease in the vertical temperature gradient and a decrease in the difference between moisture in the upper and the middle atmosphere. Yet, taken together the days with risk of thunderstorms are projected to become more frequent. / Under de senaste hundra åren har medeltemperaturen på jorden ökat med cirka 1°C, vilket har medfört förändringar i klimatet. Temperaturen kommer att fortsätta stiga på grund av den redan förhöjda halten växthusgaser i atmosfären, och om växthusgaser fortsätter släppas ut kan det förväntas bli ännu varmare. I och med att temperaturen fortsätter stiga är det mycket som pekar på att vädret i allmänhet kommer förändras, som till exempel förändrat mönster i åskoväder. I denna studie har risken för åska i ett framtida klimat studerats. Åska och konvektion bildas framförallt på grund av tre komponenter: instabilitet i atmosfären, fuktigheten i luften och en mekanism som får luften att lyftas från marken. En instabil luftmassa fås framförallt en varm sommardag när solen värmer marken, vilket medför att luften vid marken blir betydligt varmare än luften ovanför. Den andra faktorn är beroende av fuktigheten i luften, om luften är tillräckligt fuktig finns risk att större åskmoln kan bildas. De första två faktorerna kan beskrivas med vad som kallas stabilitetsindex. I denna studie beräknades risken för djup konvektion med hjälp utav stabilitetsindex. Temperatur-och fuktighetsdata från den regionala klimatmodellen RCA4, framställd på SMHI, användes för att beräkna dessa stabilitetsindex. Studien visar på att dagar med risk för åska förväntas öka i slutet av detta seklet med omkring 10-15 dagar per år över Sverige, med ännu fler dagar med risk för åska i södra Europa. En förhöjd åskrisk kan även förväntas vid bergskedjor så som svenska fjällen och Alperna. Den främsta anledningen till att åska förväntas bli vanligare är till följd av att temperaturstigningen möjliggör högre halt vattenånga i atmosfären, och därmed kommer fuktigheten i luften att öka. En längre åsksäsong har även noteras, med tidigare start i maj, och även förlängd i september.

Radiationmanagement (RM), as an option to engineer the climate, is highly controversial and suffers from a number of ethical and regulatory concerns, usually studied in the context of the objective to mitigate the global mean temperature. In this article, we discuss the idea that RM can be differentiated and scaled in several dimensions with potential objectives being to influence a certain climate parameter in a specific region. Some short-lived climate forcers (e.g., tropospheric aerosols) exhibit strong geographical and temporal variability, potentially leading to limited-area climate responses. Marine cloud brightening and thinning or dissolution of cirrus clouds could be operated at a rather local scale. It is therefore conceivable that such schemes could be applied with the objective to influence the climate at a regional scale. From a governance perspective, it is desirable to avoid any substantial climate effects of regional RM outside the target region. This, however, could prove impossible for a sustained, long-term RM. In turn, regional RM during limited time periods could prove more feasible without effects beyond the target area. It may be attractive as it potentially provides the opportunity to target the suppression of some extreme events such as heat waves. Research is needed on the traceability of regional RM, for example, using detection and attribution methods. Incentives and implications of regional RM need to be examined, and new governance options have to be conceived.

Title: Uncertainties in regional climate models outputs Author: RNDr. Eva Holtanová Supervisor: doc. RNDr. Jaroslava Kalvová, CSc. Department: Dept. of Meteorology and Environment Protection Faculty of Mathematics and Physics Charles University in Prague Present doctoral thesis focuses on the analysis of uncertainties in regional climate model outputs in the area of the Czech Republic. Generally, the uncertainties in model outputs come from inaccuracies of initial and boundary conditions, further from the necessity to parameterize the small scale processes, and the structure of the model, e.g. the choice of numerical schemes or spatial resolution. In case of the simulations of future climate, another source of uncertainty arises. It is the unknown development of forcings that influence the climate system. The analysis in this work focuses on two multi-model ensembles, that come from two international European projects PRUDENCE and ENSEMBLES. The simulated 30-year mean seasonal air temperature and precipitation amounts are used, for the reference period 1961- 1990, and several future time periods. Two techniques were employed to assess the uncertainties. The first one was aimed at dividing the variance of a multi-model ensemble into contributions of regional model, driving global model and emission...

Title: Links between atmospheric circulation and surface air temperature distributions in climate models Abstract: This thesis comprises a collection of five papers dealing with validation of regional climate model (RCM) simulations over Central Europe. The first paper illustrates and discusses problems with observed data that are used for model validation and how the choice of reference dataset affects the outcomes in validating the RCMs' performances. The second paper evaluates daily temperatures, and it indicates that some temperature biases may be related to deficiencies in the simulations of large- scale atmospheric circulation. RCMs' ability to simulate atmospheric circulation and the observed links between circulation and surface air temperatures are examined in detail in the third paper. This article also compares performances of individual RCMs with respect to the driving data by analysing the results for the driving data themselves. The fourth paper focuses on biases in the diurnal temperature range within RCMs and their possible causes by examining links of the errors to the at- mospheric circulation and cloud amount. The last paper investigates the observed relationships between atmospheric circulation and daily precipitation amounts over three regions in the Czech Republic, as well as how these...

As mudanças climáticas globais, regionais e locais representam, na atualidade, uma das maiores preocupações da humanidade. Essas mudanças podem ocorrer tanto a partir de causas naturais quanto a partir de causas antrópicas. As áreas das cidades se caracterizam por apresentarem temperaturas mais elevadas quando comparadas com as áreas rurais. Essa anomalia térmica causa a formação de ilhas de calor e esse fenômeno é reconhecidamente importante em estudos de clima urbano. O objetivo do presente trabalho foi, através de técnicas do sensoriamento remoto, identificar e analisar as ilhas de calor do Município de Piracicaba, SP verificando sua sazonalidade, intensidade e morfologia. Para tanto foi necessário realizar uma análise climática regional e verificar a possibilidade do uso do algoritmo de transformação termal do software IDRISI 3.2 nas imagens do satélite Landsat 7. Para validar o algoritmo foram aplicados dois métodos de transformação de temperatura aparente de superfície. Para a análise climática regional foram estudados os principais elementos climáticos do Município de Piracicaba, SP utilizando-se de dados da Estação Meteorológica da ESALQ/USP entre os anos de 1950 e 2005 e estes foram correlacionados com variáveis da urbanização. Concluiu-se, com os dados encontrados, que os elementos temperatura, precipitação, umidade relativa e evaporação tiveram tendência de aumento no período estudado e todos eles foram classificados como tendências climáticas. A temperatura apresentou tendência de aumento mais acentuada e se correlacionou positivamente com o aumento da urbanização. O algoritmo de transformação do software IDRISI 3.2 para o satélite Landsat 7 foi validado, sendo uma importante ferramenta para a utilização de imagens de melhor resolução. As ilhas de calor mais intensas do verão são representadas por locais com excesso de material de construção civil e pouca ou nenhuma área verde. A diferença entre a área urbana e a área rural da cidade ultrapassou 16°C no verão. O Parque da Rua do Porto é uma ilha de frescor e exerce um "efeito oásis" no centro e nos bairros vizinhos. O perfil das ilhas de calor do Município de Piracicaba não segue aquele delimitado por OKE (1974). As ilhas de calor variam sazonal e espacialmente e a intensidade destas, ao longo das estações do ano, está intimamente relacionada com a sazonalidade da cultura da cana-deaçúcar. As ilhas de calor da época da entressafra são, em média, 3.5°C mais intensas que as da época da safra. Por fim, pode-se afirmar que o uso e a cobertura do solo rural e urbano é um dos grandes agentes modificadores do clima local e regional. / Global, regional and local climate changes represent one of the greatest concerns of humanity. Climate changes can occur through natural or anthropogenic causes. Urban areas usually present higher temperatures than rural areas. This thermal effect is called "heat-island phenomenon" and has great importance on urban climate studies. In the present work, we identified and analyzed the heat-islands from Piracicaba, São Paulo using remote sensing techniques. The heat-islands were analyzed according to its seasonality, intensity and morphology using images from Landsat 7 satellite. We performed analysis on regional climate changes and investigated the use of the IDRISI thermal algorithm to convert Landsat 7 infrared thermal data on land surface temperature (LST). In order to transform Landsat 7 infrared thermal data we used two mathematical methods. Climate changes were analyzed by monitoring the climate elements for long periods of time, enabling the visualization of directional or periodical regional changes. The main climate elements were studied using data from ESALQ meteorological station for the last 55 years (1950-2005). Temperature, relative humidity, evaporation and precipitation variation were found to be correlated with urban growth parameters. The results indicated that temperature, precipitation, relative humidity and evaporation increased during the studied period and have been classified as "climate trends". The temperature presented the more accentuated trend of increase and was positively correlated with the growing urbanization. The software IDRISI 3.2 can be used with Landsat 7 high resolution images, being a useful and rapid tool to study urban heat islands. The most intense summer heatislands were represented by regions with higher amounts of constructed areas and almost any green area. In fact, during the summer the difference between the urban and rural areas was greater than 10°C. The Rua do Porto park was identified as a fresh-island and showed the "oasis effect" to the Center and neighbouring regions. Heat-islands varied according to the season and space and its intensity is intimately related to the sugar-cane seasonality. During the intercrop period the heat-islands were 3.5°C more intense than during the crop period. In conclusion land cover and land use affect local and regional climates.

Les variations du rayonnement solaire en surface (SSR) peuvent avoir un impact significatif sur divers aspects du système climatique, et notamment sur le développement socio-économique d’un pays. Pour identifier les impacts possibles du changement climatique sur le rayonnement solaire en surface à l'échelle régionale (~ 50 km) en Afrique australe jusqu'à la fin du 21ème siècle, on a analysé les données mensuelles produites dans le cadre du projet CORDEX-Afrique sur la période 1979-2099. Ces données sont issues des sorties de 5 modèles régionaux de climat (RCM) forcés par 10 modèles globaux de climat (GCM) CMIP5, pour deux scénarios d’émissions, RCP4.5 et RCP8.5, en Afrique australe (SA) et sur une partie du SWIO (0-40°S ; 0- 60°E). Pour contribuer au projet futur proposé qui vise à approfondir l'étude des changements de SSR à l'échelle locale (~ 1 km de résolution horizontale) à l'île de la Réunion et à l'île Maurice, situées dans le Sud-ouest de l'océan Indien (SWIO), près du bord d’Est du domaine CORDEX-Afrique, des simulations climatiques ont été réalisées sur trois fenêtres temporelles de 10 ans : a) le passé 1996-2005 ; et b) le futur 2046-2055 et 2090-2099, en utilisant la version 4 du RCM RegCM (RegCM4), forcé par : 1) les réanalyses climatiques ERA-Interim (ERAINT) du centre européen pour les prévisions météorologiques à moyen terme (ECMWF) pour simuler un passé récent seulement ; et 2) deux GCMs (HadGEM2-ES et GFDL-ESM2M) de l’exercice CMIP5 de simulations du climat passé et futur pour le scénario d’émissions RCP8.5 à l’échelle régionale de 50km en Afrique australe et dans le sud-ouest de l’océan Indien (0-40°S ; 0- 100°E). L’analyse de l’impact du changement climatique sur le SSR sur la base de ces simulations reste cependant limitée, à cause de leur couverture temporelle (3 périodes de 10 ans) et du nombre de modèles (2 GCMs, 1 RCM) et de scénarios (1 RCP) utilisés. Il ressort de l’analyse des simulations de l’ensemble CORDEX-Afrique que : 1) sur la période passée récente, les GCMs forceurs surestiment généralement SSR d'environ 1 W/m2 en été austral (DJF : Décembre-Janvier-Février), et de 7,5 W/m2 en hiver austral (JJA : Juin-Juillet-Août), tandis que les RCMs, forcés par ces GCMs, sous-estiment SSR d'environ -32 W/m2 et de -14 W/m2 en été et en hiver, respectivement. 2) Les projections multi-modèles de changement de SSR simulées par les RCMs et leurs GCMs forceurs sont assez cohérentes. Les GCMs prévoient, en moyenne multi-modèles, une augmentation statistiquement significative de SSR d'environ 8 W/m2 en 2099 selon le scénario RCP4.5 et de 12 W/m2 en 2099 selon le scénario RCP8.5 sur le Centre de l’Afrique australe (SA-C), et une diminution de SSR, avec un degré de confiance élevé, d'environ -5 W/m2 en 2099 selon le scénario RCP4.5 et de -10 W/m2 en 2099 selon le scénario RCP8.5, pendant la saison DJF, en Afrique équatoriale (EA-E). Dans ces deux régions, les RCMs produisent, en moyenne multi-modèles, des tendances similaires (avec un degré de confiance élevé) à celles des GCMs, mais sur des zones d’extension spatiale plus faible que celle des GCMs. Cependant, pour la saison JJA, une augmentation de SSR, d'amplitude similaire dans les simulations GCMs et RCMs (~5 W/m2 en 2099 selon le scénario RCP4.5 et 10 W/m2 selon le scénario RCP8.5), est attendue dans la région EA-E. 3). Une diminution significative de la nébulosité (environ -6% en 2099) est attendue sur le continent sud-africain pour les GCMs comme pour les RCMs. 4) Le scénario RCP8.5 produit des changements d’amplitude supérieure de 2.5W/m2 pour les GCMs forceurs et de 5W/m2 pour les RCMs en 2099 à celle pour le scénario RCP4.5. 5). Comme pour les sorties du modèle RegCM4, les structures des biais ou des changements de SSR issu des RCMs du programme CORDEX-Afrique sont globalement corrélées avec celles de couverture nuageuse totale des RCMs. L’analyse des sorties du modèle RegCM4 indique que : ..... / Changes in Surface Solar Radiation (SSR) have the potential to significantly impact diverse aspects of the climate system, and notably the socio-economic development of any nation. To identify the possible impacts of climate change on SSR at regional scales (~50 km) over Southern Africa and the South West Indian Ocean (SA-SWIO; 0-40°S ; 0- 100°E) up to the end of the 21st century, a slice downscaling experiment consisting of simulations covering three temporal windows: a) the present 1996-2005; b) the future 2046-2055 and 2090-2099 conducted with the Regional Climate Model (RCM) RegCM version 4, driven by the European Center for Medium-range Weather Forecasting (ECMWF) ERA-Interim reanalysis (ERAINT, only present) and 2 Global Climate Model (GCMs: HadGEM2-ES and GFDL-ESM2M) from the Coupled Model Intercomparison Project Phase 5 (CMIP5) under RCP8.5 scenario, are performed and evaluated. Since the slice simulation is of limited temporal coverage, number of regional and driven global models and climate change forcings, mainly because of the limit of available computational resources, the study towards a comprehensive knowledge of SSR changes in context of climate change is thus extended: an ensemble consisting of outputs from 20 regional climate downscaling realisations based on 5 RCMs that participated in the Coordinated Regional Downscaling Experiment (CORDEX) program (CORDEX-Africa) along with their 10 driving GCMs from CMIP5 covering southern Africa (0-40°S; 0- 100°E) during the period of 1990-2099 is analyzed under RCP4.5 and RCP8.5 up to 2099.The slice experiment indicates that 1) RegCM4 simulates present-day seasonal climatology, (surface air temperature, precipitation and SSR) quite well, but has a negative total cloud cover bias (about -20% in absolute percentage) when forced by the ERAINT and the two GCMs. 2) Internal variability of RegCM4-simulated annual means SSR (about 0.2 W/m2) is of one order smaller than the model bias compared with reference data. 3) RegCM4 simulates SSR changes in opposite signs when driven by the different GCMs under RCP8.5 scenario. 4) Electricity potential calculated using first-order estimation based on the RegCM simulations indicates a change less then 2% to 2099 with respect on present level.It is also found from the ensemble study that: 1) GCMs ensemble generally overestimates SSR by about 1 W/m2 in austral summer (December, January, and February, short as DJF) and 7.5 W/m2 in austral winter (June, July and August, short as JJA), while RCMs ensemble mean shows underestimations of SSR by about -32 W/m2 and -14 W/m2 in summer and winter seasons respectively when driven by GCMs. 2) Multi-model mean projections of SSR change patterns simulated by the GCMs and their embedded RCMs are fairly consistent. 3) GCMs project, in their multi-model means, a statistically significant increase of SSR of about 8 W/m2 in RCP4.5 and 12 W/m2 in RCP8.5 by 2099 over Centre Southern Africa (SA-C) and a highly confident decreasing SSR over Eastern Equatorial Africa (EA-E) of about -5 W/m2 in RCP4.5 and -10 W/m2 in RCP8.5 during the DJF season. RCMs simulate SSR change with statistical confidence over SA-C and EA-E area as well with a little spatial extension compared to GCMs. However, in the JJA season, an increase of SSR is found over EA-E of about 5 W/m2 by 2099 under RCP4.5 and 10 W/m2 under RCP8.5, of similar amplitudes in both the GCMs and RCMs simulations. 4) Significant cloudiness decrease (about -6 % to 2099) is found over continent of SA for GCMs and also shown in RCMs. 5) Larger SSR changes are found in the RCP8.5 scenario than in the RCP4.5 scenario in 2099, with about 2.5 W/m2 enhanced changes in GCMs and about 5 W/m2 in RCMs. 6) Either the biases or the changes pattern of SSR are overall correlated with the patterns of total cloud cover from RCMs in CORDEX-Africa program (for RegCM4 as well). The slice experiment indicates that ...

Die vorliegende Arbeit 'Abflu&szlig;entwicklung in Teileinzugsgebieten des Rheins - Simulationen f&uuml;r den Ist-Zustand und f&uuml;r Klimaszenarien' untersucht Auswirkungen m&ouml;glicher zuk&uuml;nftiger Klima&auml;nderungen auf das Abflu&szlig;geschehen in ausgew&auml;hlten, durch Mittelgebirge gepr&auml;gten Teileinzugsgebieten des Rheins: Mosel (bis Pegel Cochem); Sieg (bis Pegel Menden 1) und Main (bis Pegel Kemmern).<br><br>In einem ersten Schritt werden unter Verwendung des hydrologischen Modells HBV-D wichtige Modellprozesse entsprechend der Einzugsgebietscharakteristik parametrisiert und ein Abbild der Gebietshydrologie erzeugt, das mit Zeitreihen gemessener Tageswerte (Temperatur, Niederschlag) eine Zeitreihe der Pegeldurchfl&uuml;sse simulieren kann. Die G&uuml;te der Simulation des Ist-Zustandes (Standard-Me&szlig;zeitraum 1.1.1961-31.12.1999) ist f&uuml;r die Kalibrierungs- und Validierungszeitr&auml;ume in allen Untersuchungsgebieten gut bis sehr gut.<br>Zur Erleichterung der umfangreichen, zeitaufwendigen einzugsgebietsbezogenen Datenaufbereitung f&uuml;r das hydrologische Modell HBV-D wurde eine Arbeitsumgebung auf Basis von Programmerweiterungen des Geoinformationssystems ArcView und zus&auml;tzlichen Hilfsprogrammen entwickelt. Die Arbeitsumgebung HBV-Params enth&auml;lt eine graphische Benutzeroberfl&auml;che und r&auml;umt sowohl erfahrenen Hydrologen als auch hydrologisch geschulten Anwendern, z.B. Studenten der Vertiefungsrichtung Hydrologie, Flexibilit&auml;t und vollst&auml;ndige Kontrolle bei der Ableitung von Parameterwerten und der Editierung von Parameter- und Steuerdateien ein. Somit ist HBV-D im Gegensatz zu Vorl&auml;uferversionen mit rudiment&auml;ren Arbeitsumgebungen auch au&szlig;erhalb der Forschung f&uuml;r Lehr- und &Uuml;bungszwecke einsetzbar.<br><br>In einem zweiten Schritt werden Gebietsniederschlagssummen, Gebietstemperaturen und simulierte Mittelwerte des Durchflusses (MQ) des Ist-Zustandes mit den Zust&auml;nden zweier Klimaszenarien f&uuml;r den Szenarienzeitraum 100 Jahre sp&auml;ter (2061-2099) verglichen. Die Klimaszenarien beruhen auf simulierten Zirkulationsmustern je eines Modellaufes zweier Globaler Zirkulationsmodelle (GCM), die mit einem statistischen Regionalisierungsverfahren in Tageswertszenarien (Temperatur, Niederschlag) an Me&szlig;stationen in den Untersuchungsgebieten &uuml;berf&uuml;hrt wurden und als Eingangsdaten des hydrologischen Modells verwendet werden.<br>F&uuml;r die zweite H&auml;lfte des 21. Jahrhunderts weisen beide regionalisierten Klimaszenarien eine Zunahme der Jahresmittel der Gebietstemperatur sowie eine Zunahme der Jahressummen der Gebietsniederschl&auml;ge auf, die mit einer hohen Variabilit&auml;t einhergeht. Eine Betrachtung der saisonalen (monatlichen) &Auml;nderungsbetr&auml;ge von Temperatur, Niederschlag und mittlerem Durchflu&szlig; zwischen Szenarienzeitraum (2061-2099) und Ist-Zustand ergibt in allen Untersuchungsgebieten eine Temperaturzunahme (h&ouml;her im Sommer als im Winter) und eine generelle Zunahme der Niederschlagssummen (mit starken Schwankungen zwischen den Einzelmonaten), die bei der hydrologischen Simulation zu deutlich h&ouml;heren mittleren Durchfl&uuml;ssen von November bis M&auml;rz und leicht erh&ouml;hten mittleren Durchfl&uuml;ssen in den restlichen Monaten f&uuml;hren. Die St&auml;rke der Durchflu&szlig;erh&ouml;hung ist nach den individuellen Klimaszenarien unterschiedlich und im Sommer- bzw. Winterhalbjahr gegenl&auml;ufig ausgepr&auml;gt. Hauptursache f&uuml;r die simulierte starke Zunahme der mittleren Durchfl&uuml;sse im Winterhalbjahr ist die trotz Temperaturerh&ouml;hung der Klimaszenarien winterlich niedrige Evapotranspiration, so da&szlig; erh&ouml;hte Niederschl&auml;ge direkt in erh&ouml;hten Durchflu&szlig; transformiert werden k&ouml;nnen.<br>Der Vergleich der Untersuchungsgebiete zeigt in Einzelmonaten von West nach Ost abnehmende &Auml;nderungsbetr&auml;ge der Niederschlagssummen, die als Hinweis auf die Bedeutung der Kontinentalit&auml;tseinfl&uuml;sse auch unter ge&auml;nderten klimatischen Bedingungen in S&uuml;dwestdeutschland aufgefa&szlig;t werden k&ouml;nnten.<br>Aus den regionalisierten Klimaszenarien werden &Auml;nderungsbetr&auml;ge f&uuml;r die Modulation gemessener Zeitreihen mittels synthetischer Szenarien abgeleitet, die mit einem geringen Rechenaufwand in hydrologische Modellantworten &uuml;berf&uuml;hrt werden k&ouml;nnen. Die direkte Ableitung synthetischer Szenarien aus GCM-Ergebniswerten (bodennahe Temperatur und Gesamtniederschlag) an einzelnen GCM-Gitterpunkten erbrachte unbefriedigende Ergebnisse.<br>Ob, in welcher H&ouml;he und zeitlichen Verteilung die in den (synthetischen) Szenarien verwendeten Niederschlags- und Temperatur&auml;nderungen eintreten werden, kann nur die Zukunft zeigen. Eine Absch&auml;tzung, wie sich die Abflu&szlig;verh&auml;ltnisse und insbesondere die mittleren Durchfl&uuml;sse der Untersuchungsgebiete bei m&ouml;glichen &Auml;nderungen entwickeln w&uuml;rden, kann jedoch heute schon vorgenommen werden. <br><br>Simulationen auf Szenariogrundlagen sind ein Weg, unbekannte zuk&uuml;nftige Randbedingungen sowie regionale Auswirkungen m&ouml;glicher &Auml;nderungen des Klimasystems ausschnittsweise abzusch&auml;tzen und entsprechende Risikominderungsstrategien zu entwickeln. Jegliche Modellierung und Simulation nat&uuml;rlicher Systeme ist jedoch mit betr&auml;chtlichen Unsicherheiten verkn&uuml;pft. Vergleichsweise gro&szlig;e Unsicherheiten sind mit der zuk&uuml;nftigen Entwicklung des sozio&ouml;konomischen Systems und der Komplexit&auml;t des Klimasystems verbunden. Weiterhin haben Unsicherheiten der einzelnen Modellbausteine der Modellkette Emissionsszenarien/Gaszyklusmodelle - Globale Zirkulationsmodelle/Regionalisierung - hydrologisches Modell, die eine Kaskade der Unsicherheiten ergeben, neben Datenunsicherheiten bei der Erfassung hydrometeorologischer Me&szlig;gr&ouml;&szlig;en einen erheblichen Einflu&szlig; auf die Vertrauensw&uuml;rdigkeit der Simulationsergebnisse, die als ein dargestellter Wert eines Ergebnisbandes zu interpretieren sind.<br><br>Der Einsatz <br>(1) robuster hydrologischer Modelle, die insbesondere temperaturbeeinflu&szlig;te Prozesse ad&auml;quat beschreiben,<br>(2) die Verwendung langer Zeitreihen (wenigsten 30 Jahre) von Me&szlig;werten und<br>(3) die gleichzeitige vergleichende Betrachtung von Klimaszenarien, die auf unterschiedlichen GCMs beruhen (und wenn m&ouml;glich, verschiedene Emissionsszenarien ber&uuml;cksichtigen),<br>sollte aus Gr&uuml;nden der wissenschaftlichen Sorgfalt, aber auch der besseren Vergleichbarkeit der Ergebnisse von Regionalstudien im noch jungen Forschungsfeld der Klimafolgenforschung beachtet werden. / This thesis 'Development of runoff in subcatchments of the River Rhine - simulations of the current state and for climate change scenarios' investigates the impacts of possible future climate changes on runoff and runoff regime in selected subcatchments of the River Rhine. The regional climate in the selected subcatchments Mosel (up to gauge Cochem), Sieg (gauge Menden 1) and Main (gauge Kemmern) is affected by the middle mountain ranges.<br><br>In a first step, important model processes are parameterized according to catchment characteristics. A representation of the regional hydrology is then produced by using the hydrological model HBV-D. Based on time series of daily measurements (temperature, precipitation) at stations within the catchment, this representation can be used to realistically simulate time series of runoff and discharge. <br>In all examined areas, the quality of simulations of the calibration and validation periods for the current state (standard period of measurements 01/01/1961-12/31/1999) can be regarded as good to excellent. <br>To aid the catchment-specific, extensive and time-consuming data processing, a working environment for the hydrological model HBV-D has been developed. It is based on program extensions of the geographical information system ArcView and further programs. The working environment HBV-Params contains a graphical interface that gives both experienced hydrologists and students full control and enables them to flexibly derive parameter values and edit parameter and control files. In contrast to previous versions with only rudimentary working environments, HBV-D can therefore be utilized for research as well as for educational purposes. <br><br>In a second step, the current states of areal precipitation, areal temperature and simulated mean discharge (MQ) are compared to the corresponding states for two scenarios of future climate changes (100 years later, 2061-2099). These scenarios are based on simulated global circulations of one model run for each of two global circulation models (GCM). These global circulations are regionalized (downscaled) using a statistical approach into scenario time series of daily values (temperature, precipitation - input for the hydrological model) at control stations within the individual catchments. <br>For the second half of the 21st century, both regionalized climate change scenarios indicate increases in the mean annual areal temperature and mean annual sum of precipitation, along with a high variability of the latter. The seasonal (monthly) changes in temperature, precipitation and mean discharge between scenario state (2061-2099) and current state indicate increases in temperature (higher in summer than in winter) as well as a general increase in precipitation sums (strong fluctuations between individual months). In the hydrological simulations for all investigated catchments, this results in considerably higher mean discharges from November to March and small increases in mean discharge for the other months. The magnitude of the increases in discharge depends on the individual climate change scenario, one showing higher increases than the other during the summer half-year and vice versa for the winter half-year. The main reason for the simulated strong increase in mean discharge during winter half-year is, in spite of higher temperatures, the still relatively low evapotranspiration which allows higher precipitation to be directly transformed into higher discharges. <br>The comparison of the investigated catchments shows decreasing amounts of changes in the sum of precipitation from West to East in individual months. This indicates the importance of continentality under changed climatic conditions in Southwest Germany. <br>For the modification of measured time series (temperature, precipitation), which can be easily converted as synthetic scenarios into simulated hydrological results, amounts of change are derived from regionalized (downscaled) climate change scenarios. The derivation of synthetic scenarios directly from GCM output at individual GCM gridpoints yielded unsatisfactory results. <br>Only the future itself can show whether the timing and amount of changes in temperature and precipitation used in (synthetic) climate change scenarios come close to reality. An assessment of possible developments in runoff regime and specifically mean discharge under possible changed climatic conditions in the investigated catchments is already feasible today. <br><br>Simulations based on scenarios are one way to establish unknown future boundary conditions for the estimation of regional impacts of possible changes of the climate system. Nevertheless, all types of modeling and simulation of natural systems are linked with uncertainties. Rather large uncertainties persist regarding the future development of the socio-economic system and the complexity of the climate system and earth system. Furthermore, besides data uncertainties associated with the measurement of hydro-meteorological values, uncertainties associated with individual components of the model chain emission scenarios/gas cycle model - GCM/regionalization - hydrological model, which form a cascade of uncertainty, have a great influence on the trustworthiness of the simulation results (which are understood as one shown value within a range of results). <br><br>In the young field of climate impact research the use of <br>(1) robust hydrological models that adequately describe temperature-dependent processes,<br>(2) long time series (at least 30 years long) of measurements, <br>(3) concurrent comparisons of climate change scenarios, based on different GCMs (and, if possible, different emission scenarios)<br>should be considered for reasons of scientific thoroughness and to improve comparability of regional impact studies.

Die vorliegende Arbeit befasst sich mit der Betrachtung der regionalen Klimawandelfolgen auf die landwirtschaftlichen Erträge des agrarintensiven Landes Niedersachsen. Zu diesem Zweck wurde das neuentwickelte robuste Pflanzenmodell BioStar herangezogen um mittels hochaufgelösten (100 × 100 m) Wettreg Klimadaten des 21. Jahrhunderts die Entwicklung der Biomasseerträge von vier Wintergetreiden (Weizen, Gerste, Roggen & Triticale), drei Maissorten (differenziert nach Reifezeitpunkt) und drei weiterer Feldfrüchte (Sonnenblume, Sorghum & Sommerweizen) zu modellieren. Bei dem Pflanzenmodell BioStar handelt es sich um ein kohlenstoffbasiertes Pflanzenmodell, mit dem anhand von Eingangsklimadaten (Niederschlagshöhe, Temperatur, Globalstrahlung, Luftfeuchte und Windgeschwindigkeit) und dem verfügbaren Bodenwasser (Feldkapazität) der Ertragszuwachs im Verlauf der Vegetationsperiode simuliert wird. Das Modell eignet sich für die Thematik insbesondere auch deshalb, da es an der Universität Göttingen entwickelt und auf Niedersächsischen Standorten validiert wurde. Die zur Modellierung benötigten Bodenparameter wurden der Niedersächsischen BÜK50n entnommen. Dabei kamen nur Flächen zur Anwendung, die nach der Corine Landbedeckungserhebung von 2005 zu den landwirtschaftlich genutzten Flächen in Niedersachsen zählen. Die mittlere Größe dieser gut 90.000 Flächen liegt damit um 33 ha. Die Entwicklung wird unter Berücksichtigung des IPCC Szenarios A1B sowie des CO2-Düngeeffekts bis zum Ende des Jahrhunderts pflanzenabhängig stagnierend bis deutlich positiv verlaufen, wovon allerdings nicht alle Regionen in gleicher Weise profitieren können. Insgesamt verschieben sich die landwirtschaftlichen Gunstgebiete weiter nach Westen — was aber durch die bessere Entwicklung des Westens und nicht in einer negativen Entwicklung der östlichen Flächen begründet ist. Das Ostbraunschweigische Hügelland ist meist unter den Regionen mit der besten Entwicklung, kann im absoluten Vergleich aber nie zu den guten landwirtschaftlichen Standorten aufschließen. Größter Verlierer wird den Ergebnissen nach das südliche Hügelland sein, das über die kommenden Jahrzehnte zusehends schlechtere Voraussetzungen für den Pflanzenanbau bietet. Die gesamte Entwicklung wird dabei aber erst ab etwa der Jahrhunderthälfte einsetzen, vorher lassen sich für den Großteil der Pflanzen kaum Veränderungen konstatieren. In den kommenden 20 Jahren zeigt nur die Gerste deutliche Anzeichen eines Ertragszuwachses und mittelreifender Mais eines Ertragsrückgangs. Bis 2099 kehrt sich dieser Trend dann wieder um. Eigentlich alle Feldfrüchte zeigen spätestens zum Jahrhundertende eine positive Entwicklungstendenz, wenn Winterweizen, Winterroggen und Wintertriticale auch nur vergleichsweise schwach. Die beiden hauptausschlaggebenden Entwicklungsfaktoren werden in Zukunft zum einen die atmosphärische CO2-Konzentration sein, über deren Düngeeffekt die Erträge positiv beeinfluss werden. Ihr stehen die abnehmenden Sommerniederschläge gegenüber, die sich deutlich negativ auf die Erträge auswirken. Vieles wird in Zukunft davon abhängen, inwieweit diese Niederschläge tatsächlich zurückgehen werden und wie stark der CO2-Düngeeffekt tatsächlich ausfallen wird. Ungeachtet dessen werden sich aber die Wintergerste und der Sommerweizen dennoch tendenziell positiv entwickeln können, da beider Entwicklung relativ unabhängig von den CO2- Konzentrationen verläuft, wobei die Gerste zusätzlich weniger anfällig auf sinkende Sommerniederschläge reagiert. Interessant wird auch die Entwicklung des Maises werden. Im Gegensatz zu anderen Studien die nur mit „Mais“ modellieren, wurde hier auf früh-, mittel- und spätreifende Sorten zurückgegriffen. Die unterschiedlichen Sorten besitzen über das Jahrhundert deutlich größere Unterschiede als etwa die Arten Weizen, Roggen und Triticale. Während mittelreifender Mais die schlechtesten Aussichten, eigentlich unter allen behandelten Pflanzen, besitzt, wird spätreifender Mais mit den deutlichsten Ertragszuwächsen im kommenden Jahrhundert rechnen können.