As trocas de calor entre o piso e o solo de edificações térreas é um dos aspectos mais influentes em seu desempenho térmico e energético. No entanto, devido à complexidade dos métodos de cálculo e à escassez de estudos nessa área, há ainda um grande número de incertezas quanto à sua modelagem em programas de simulação computacional. O objetivo principal desta pesquisa é identificar a forma mais correta para a modelagem das trocas de calor entre o piso e o solo de edificações térreas no programa de simulação de desempenho EnergyPlus, com o uso do pré-processador Slab. A metodologia consiste na verificação do impacto de distintas alternativas de modelagem e na comparação entre as temperaturas da interface piso e solo medidas em célula-teste e simuladas com o Slab. Com a verificação do impacto das alternativas de modelagem foi possível identificar a forma mais correta de modelagem do Slab e os parâmetros de entrada com maior impacto no desempenho térmico de uma habitação de interesse social. Já a medição em célula-teste permitiu analisar a relação entre a evolução das temperaturas da célula-teste e do solo. Verificou-se que a temperatura externa do ar (média mensal) apresenta valores bastante próximos à temperatura do solo, sugerindo que utilizar a temperatura externa pode ser uma alternativa quando não há dados do solo. Com esses dados, foi possível desenvolver simulações paramétricas com diferentes combinações de parâmetros de entrada e comparar a temperatura da interface piso e solo simulada pelo Slab com a medida. Os resultados indicaram que o Slab funciona corretamente e que gera valores de temperatura da interface piso e solo muito próximos da realidade quando este utiliza parâmetros de entrada adequados. Foi verificado também o alto potencial de impacto dos parâmetros de entrada: evapotranspiração, albedo e as propriedades do solo nos resultados do Slab. Além disso verificou-se que, o uso de outras alternativas de modelagem, no lugar do Slab, gera uma diferença muito significativa, com variação de -26,2 a -55,2% nos graus-hora de desconforto totais de uma edificação. Por fim, como síntese dessa pesquisa, foi elaborado um Manual do Slab com o objetivo de auxiliar e incentivar o uso do pré-processador / The heat exchanges between the floor and the ground of a single-story slab-on-grade building is one of the most influential aspects in its thermal and energy performance. However, due to the calculation methods complexity and the scarcity of studies in this area, there are still a great number of uncertainties regarding its modeling in computer simulation programs. The main objective of this research is to identify the most correct way to model heat exchanges between the floor and the ground of a single-story slab-on-grade building in the EnergyPlus performance simulation program using the Slab preprocessor. The methodology consists of verifying the impact of different modeling alternatives and comparing the temperature of the ground and floor interface measured in test cells and simulated with Slab. With the impact verification of the modeling alternatives, it was possible to identify the most correct way of Slab modeling and the input parameters with the greatest impact on the thermal performance of a social housing. The test-cell measurement has allowed analyzing the relationship between the evolution of test-cell and soil temperatures. It was verified that the external air temperature (monthly average) presents very close values to the soil temperature, suggesting that using the external temperature can be an alternative when there is no soil data. With these data, it was possible to develop parametric simulations with different input parameters combinations and to compare the temperature of the ground and floor interface simulated by Slab with the measurement. The results indicated that Slab works correctly and generates values of temperature of the ground and floor interface very close to reality when it uses appropriate input parameters. It was also verified the high impact potential of the input parameters: evapotranspiration, albedo and soil properties in the Slab results. In addition, it was verified that the use of other modeling alternatives, in place of Slab, generates a very significant difference, varying from -26.2 to -55.2% in the total discomfort degrees of a building. Finally, as a synthesis of this research, a Slab Manual was developed with the purpose to assist and encourage the preprocessor use

As trocas de calor entre o piso e o solo de edificações térreas é um dos aspectos mais influentes em seu desempenho térmico e energético. No entanto, devido à complexidade dos métodos de cálculo e à escassez de estudos nessa área, há ainda um grande número de incertezas quanto à sua modelagem em programas de simulação computacional. O objetivo principal desta pesquisa é identificar a forma mais correta para a modelagem das trocas de calor entre o piso e o solo de edificações térreas no programa de simulação de desempenho EnergyPlus, com o uso do pré-processador Slab. A metodologia consiste na verificação do impacto de distintas alternativas de modelagem e na comparação entre as temperaturas da interface piso e solo medidas em célula-teste e simuladas com o Slab. Com a verificação do impacto das alternativas de modelagem foi possível identificar a forma mais correta de modelagem do Slab e os parâmetros de entrada com maior impacto no desempenho térmico de uma habitação de interesse social. Já a medição em célula-teste permitiu analisar a relação entre a evolução das temperaturas da célula-teste e do solo. Verificou-se que a temperatura externa do ar (média mensal) apresenta valores bastante próximos à temperatura do solo, sugerindo que utilizar a temperatura externa pode ser uma alternativa quando não há dados do solo. Com esses dados, foi possível desenvolver simulações paramétricas com diferentes combinações de parâmetros de entrada e comparar a temperatura da interface piso e solo simulada pelo Slab com a medida. Os resultados indicaram que o Slab funciona corretamente e que gera valores de temperatura da interface piso e solo muito próximos da realidade quando este utiliza parâmetros de entrada adequados. Foi verificado também o alto potencial de impacto dos parâmetros de entrada: evapotranspiração, albedo e as propriedades do solo nos resultados do Slab. Além disso verificou-se que, o uso de outras alternativas de modelagem, no lugar do Slab, gera uma diferença muito significativa, com variação de -26,2 a -55,2% nos graus-hora de desconforto totais de uma edificação. Por fim, como síntese dessa pesquisa, foi elaborado um Manual do Slab com o objetivo de auxiliar e incentivar o uso do pré-processador / The heat exchanges between the floor and the ground of a single-story slab-on-grade building is one of the most influential aspects in its thermal and energy performance. However, due to the calculation methods complexity and the scarcity of studies in this area, there are still a great number of uncertainties regarding its modeling in computer simulation programs. The main objective of this research is to identify the most correct way to model heat exchanges between the floor and the ground of a single-story slab-on-grade building in the EnergyPlus performance simulation program using the Slab preprocessor. The methodology consists of verifying the impact of different modeling alternatives and comparing the temperature of the ground and floor interface measured in test cells and simulated with Slab. With the impact verification of the modeling alternatives, it was possible to identify the most correct way of Slab modeling and the input parameters with the greatest impact on the thermal performance of a social housing. The test-cell measurement has allowed analyzing the relationship between the evolution of test-cell and soil temperatures. It was verified that the external air temperature (monthly average) presents very close values to the soil temperature, suggesting that using the external temperature can be an alternative when there is no soil data. With these data, it was possible to develop parametric simulations with different input parameters combinations and to compare the temperature of the ground and floor interface simulated by Slab with the measurement. The results indicated that Slab works correctly and generates values of temperature of the ground and floor interface very close to reality when it uses appropriate input parameters. It was also verified the high impact potential of the input parameters: evapotranspiration, albedo and soil properties in the Slab results. In addition, it was verified that the use of other modeling alternatives, in place of Slab, generates a very significant difference, varying from -26.2 to -55.2% in the total discomfort degrees of a building. Finally, as a synthesis of this research, a Slab Manual was developed with the purpose to assist and encourage the preprocessor use

Les régions de haute latitude sont actuellement les plus sensibles aux effets du réchauffement climatique, et avec des élévations de température pouvant atteindre les 3 à 8 ◦C au niveau du pôle sur les 100 prochaines années. Les pergélisols (sols présentant des températures négatives deux années consécutives) sont présents sur 25 % des terres émergées de l’hémisphère nord et contiennent de grandes quantités de carbone « gelé », estimées à 1400 Gt (40 % de la quantité de carbone terrestre global). Des études récentes ont montré qu’une partie non négligeable (50 %) des premiers mètres des pergélisols pourraient fondre d’ici 2050, et 90 % d’ici 2100. Le but de l’étude est donc d’améliorer les moyens de suivi de l’évolution des températures du sol dans les zones arctiques, et plus particulièrement dans les régions couvertes de neige. L’objectif est de décrire la température du sol tout au long de l’année y compris sous un manteau neigeux, et d’analyser l’évolution de l’épaisseur de la couche active des pergélisols en relation avec la variabilité du climat. Nous utilisons des données satellites (fusion de données de température dans l’infra-rouge thermique “LST” et de température de brillance micro-onde AMSR-E « Tb ») assimilées dans le schéma de surface du modèle climatique canadien (CLASS, V 3.6) couplé à un modèle simple de transfert radiatif (HUT). Cette approche bénéficie des avantages de chaque type de donnée de manière à réaliser deux objectifs spécifiques : 1-construire une méthodologie solide permettant de retrouver les températures du sol, avec et sans neige, en zone de toundra, et 2-à partir de ces températures du sol, dériver la durée de fonte estivale et l’épaisseur de la couche active du pergélisol. Nous décrivons le couplage des modèles ainsi que la méthodologie permettant l’ajustement des paramètres météorologiques d’entrée du modèle CLASS (essentiellement les températures de l’air et les précipitations issues de la base de données des réanalyses météorologiques NARR) de manière à minimiser les LST et Tb simulées en comparaison aux mesures satellites. Par rapport aux données de mesures de sol de stations météorologiques prises comme référence pour validation dans les zones de toundra d’Amérique du Nord, les résultats montrent que la méthode proposée améliore significativement la simulation des températures du sol lorsqu’on utilise les données LST MODIS et Tb à 10 et 19 GHz pour contraindre le modèle, en comparaison avec les sorties du modèle sans les données satellites. Dans ce processus d’inversion, la correction de l’évolution des conditions de neige au cours de l’hiver contrainte avec le rapport de polarisation à 11 GHz constitue une approche originale. Une analyse de l’erreur pour 4 sites de toundra et sur plusieurs années (18 cas) est effectuée pour la période estivale (1,7 -3,6 K) ainsi que pour la période hivernale couverte de neige (1,8 -3,5 K). L’indice des degrés-jours de fontes annuel, dérivé des températures du sol simulés par notre approche, permet de cartographier les zones de pergélisols continu en accord avec les cartes actuelles. Un meilleur suivi des processus d’évolution des pergélisols, et tout particulièrement de l’impact de la couverture de neige, devrait permettre une meilleure compréhension des effets du réchauffement climatique sur la fonte des pergélisols et l’avenir de leurs stocks de carbone. / Abstract : High latitude areas currently are the most sensitive to global warming effects. In the next 100 years, temperature could rise up to 3 to 8 ◦C at the North Pole. Permafrost (ground with negative temperatures two years in a row) represents 25% of northern hemisphere lands, and contains huge quantities of "frozen" carbon estimated at 1400 Gt (40 % of the global terrestrial carbon). Recent studies showed that a part (50 %) of the permafrost first few meters could melt by 2050, and 90 % by 2100. The goal of our study is to improve our understanding of ground temperature evolution in arctic areas, especially in snow covered regions. The objective is to discribe the ground temperature all year long with and without a snow cover, and to analyze the evolution of the permafrost’s active layer in relation with the climate variability. We use remote sensing data (fuzzed of MODIS "LST" surface temperatures and AMSR-E "Tb" brightness temperatures) assimilated in the canadian landscape surface scheme (CLASS) coupled to a simple radiative transfer model (HUT). This approach takes into account the advantages of each kind of data in order to achieve two objectives : 1 - build a solid methodology allowing to retrieve ground temperatures, with and without a snow cover, in tundra areas ; 2 - from those retrieved ground temperatures, derive the summer melting duration which can be linked to the permafrost active layer thickness. We describe the models coupling as well as the methodology allowing the adjustement of CLASS input meteorological parameters (essentially the air temperatures and precipitations from the NARR meteorological data base) in order to minimize the simulated LST and Tb in comparison to remote sensing data. By using meteorological station’s ground temperature measurments as a reference for validation in North America tundra areas, results show that the proposed method improves the simulation of ground temperatures when using LST MODIS and Tb at 10 and 19 GHz data to constrain the model, in comparison with model outputs without satellite data. Using the Tb polarization ratio H/V at 10 GHz allows an improvement of the constrain on winter period simulations. An analyze of the error is conducted for summer (1,7 - 3,6 K) and winter (1,8 - 3,5 K). We present climatic applications for future work that meets the second objective of the Ph.D. A better understanding of evolution processes of permafrost, and particularly of the impact of the snow cover, should allow us a better understanding of global warming effects on the permafrost’s melting and the future of their carbon stocks.

Forests affect climate by absorbing CO₂ but also by altering albedo, latent heat flux, and sensible heat flux. In this study we used the Community Earth System Model to assess the biophysical effect of North American temperate forests on climate and how this effect changes with location, tree type, and forest management. We calculated the change in annual temperature and energy balance associated with afforestation with either needle leaf evergreen trees (NET) or broadleaf deciduous trees (BDT) and between forests with high and low leaf-area indices (LAI). Afforestation from crops to forests resulted in lower albedo and higher sensible heat flux but no consistent difference in latent heat flux. Forests were consistently warmer than crops at high latitudes and colder at lower latitudes. In North America, the temperature response from afforestation shifted from warming to cooling between 34° N and 40° N for ground temperature and between 21° N and 25° N for near surface air temperature. NET tended to have lower albedo, higher sensible heat flux and warmer temperatures than BDT. The effect of tree PFT was larger than the effect of afforestation in the south and in the mid-Atlantic. Increasing LAI, a proxy for increased management intensity, caused a cooling effect in both tree types, but NET responded more strongly and albedo decreased while albedo increased for BDT. Our results show that forests' location, tree type, and management intensity can have nearly equal biophysical effects on temperature. A forest will have maximum biophysical cooling effect if it is in the south, composed of broadleaf PFT, and is managed to maximize leaf area index. / Master of Science