Solar parks are increasingly getting a larger market share of PV installations over the world, and have for the last couple of years managed to establish itself in the Swedish market. The market has for a long time been known for its decline in module prices, which has allowed an emergence of more efficient PV-techniques such as one-axis trackers and bifacial modules. Bifacial modules use the backside of modules for improved utiliziation of incoming light, while one-axis trackers have the ability to track the sun in order to maximise light absorption. These innovations have now caught the interest of companies willing to invest in large-scale PV-farms, where efficient land use is highly regarded. The aim of this thesis was to examine how bifacial modules and one-axis trackers perform in terms of system performance and profitabilty if implemented in 'Solpark Fyrislund', a solar park owned by Vasakronan AB. This was done by modelling and simulating cases in which said techniques were incorporated. The data was later used to estimate profitabilty of each investigated case. Results showed that the highest system performance and profitability was achieved by installing bifacial modules on the site. One-axis trackers are currently too expensive, require higher maintenance and has a higher demand for land, resulting in its profitability not being justified. It was also found that the current configuration could be optimized further for higher profit, by slightly reducing the pitch as well as increasing the tilt of the existing modules. The study should be followed up by further investigating the use of backtracking for one-axis trackers. Said innovations should also be more established in the Swedish market so that CAPEX- and OPEX prices become more accessible.

Markmonterade solcellsanläggningar i norra Sverige behöver ta hänsyn till förekomsten av snö och risken för markinterferens, vilket innebär att snömängden i framkant av panelerna gör att den snö som ackumuleras ovanpå inte kan glida av. Följden blir skuggning av panelerna som därmed får nedsatt eller helt utebliven elproduktion. Syftet med arbetet var att besvara frågeställningar kring vilken montagehöjd som krävs för att undvika problemet samt om den ökade engångskostnaden kompenseras av potentialen till ökad produktion under vintermånaderna. Metoden bestod främst av att jämföra produktionsdata från en solpark i Östersund med värden för solinstrålning och snödjup från SMHI för att avgöra vilken effekt snöskuggning haft på produktionen och hur utfallet skulle ha sett ut vid olika monteringshöjder av anläggningen. Resultaten visar att det finns stor potential till goda produktionsvärden under vårvintern, förutsatt att markinterferens inte finns närvarande. Anledningen beror troligtvis på högt albedo från snötäckt mark och lägre lufttemperaturer vilket har en positiv inverkan på modulernas verkningsgrad. En beräkningsmodell utvecklades för att uppskatta en lämplig monteringshöjd för en solpark utifrån dess tänkta utformning och det förväntade snödjupet på platsen. Förhoppningen är att modellen kan bidra till ökad kunskap för att främja utbyggnad av markmonterade solcellsanläggningar även på nordliga breddgrader. Lönsamheten för ett högre montage undersöktes genom en jämförelse mellan ett prisexempel från en uppförd solpark och ett uppskattat produktionsbortfall från solparken i Östersund vid en teoretiskt lägre monteringshöjd. Det visade att en höjning av Östersundsparken från 50 till 90 centimeter skulle betala av sig enbart genom tillskottet i produktion under perioden februari till april de tre första vintrarna. / Ground-mounted PV installations in northern Sweden need to consider the presence of snow and the risk of ground interference, meaning that the buildup of snow in front of the panels prevents the snow accumulated on top from sliding off. The result is shading of the panels, which in turn reduces or eliminates the electricity production. The purpose of this work was to answer questions regarding the mounting height required to avoid this problem and whether the increased one-time cost for higher mounting is compensated for by the enhanced production during winter months. The method consisted mainly of comparing production data from a solar park in Östersund to solar radiation values and snow depth from SMHI to determine the effect of snow shading on production and the outcome at different installation heights of the plant. The results showed that there is great potential for valuable energy production during the late winter season, provided that ground interference is not present. This is probably due to high albedo from snow-covered ground and lower air temperatures resulting in a positive impact on the efficiency of the modules. A computational model was developed to estimate a suitable mounting height for a solar park based on the intended design and expected snow depth at the site. The intention is that the model can contribute to increased knowledge to promote the deployment of ground-mounted PV systems in northern latitudes. The profitability of higher mounting was investigated by comparing a price example from an existing solar facility and an estimated production loss from the solar park in Östersund at a theoretical lower mounting height. It showed that  increasing the height of the Östersund site from 50 to 90 centimeters in front would pay off solely on the enhanced production during the period February to April of the first three winters.

L'albédo, fraction de rayonnement réfléchi dans le spectre solaire, est une variable clef du bilan énergétique des surfaces enneigées et englacées. Cette grandeur possède une forte variabilité spatio-temporelle ce qui fait de la télédétection un outil adapté pour son étude. L'albédo dépend à la fois des propriétés physiques du milieu considéré et des caractéristiques du rayonnement incident. Les différentes grandeurs liées à l'albédo sont fonction des domaines angulaires et spectraux des radiations considérées. Les mesures de répartition angulaire du rayonnement réfléchi par la neige ont montré que l'hypothèse lambertienne pouvait conduire à des erreurs non négligeables lors de la détermination de l'albédo par télédétection. La connaissance des caractéristiques de la répartition angulaire du rayonnement réfléchi par la neige permet de développer une nouvelle méthode de détermination de l'albédo en zones montagneuses. Cette méthode prend en compte les effets liés à la forte variabilité topographique des terrains de montagne, à l'anisotropie du rayonnement réfléchi par la neige et par la glace ainsi que les variations spectrales de l'albédo en fonction des propriétés physiques de la surface. Elle a été appliquée à deux types de données : des photographies terrestres visibles et proche infrarouges (résolution spatiale 10 m) et des images MODIS (résolution spatiale 250 m). L'incertitude sur la valeur de l'albédo ainsi déterminée est évaluée à ±10% grâce aux mesures de terrain effectuées sur le glacier de Saint Sorlin (massif des Grandes Rousses, France). L'étude des cartes d'albédo issues de dix années (2000-2009) d'images MODIS montre qu'il n'y a pas de décroissance marquée de la valeur de l'albédo en zone d'ablation au contraire de ce qui a été prouvé pour le glacier du Morteratsch (Suisse). De plus, il existe une corrélation très élevée entre la valeur minimale de la moyenne de l'albédo sur le glacier, i.e. l'albédo moyen du glacier le jour où la ligne de neige est proche de la ligne d'équilibre, et la valeur du bilan de masse annuel spécifique. L'assimilation des données d'albédo obtenues grâce aux images MODIS et aux photographies terrestres dans le modèle de neige CROCUS permet une bonne estimation du bilan de masse spatialisé du glacier de Saint Sorlin (rmse=0.5 m w.e. pour les cinq années hydrologiques étudiées). Les forçages météorologiques utilisés pour cette étude sont de moyenne échelle. L'analyse succincte de la contribution des différents flux atmosphériques au bilan d'énergie de surface montre qu'en zone d'ablation comme en zone d'accumulation, le bilan radiatif net courtes longueurs d'ondes constitue la source principale d'énergie et que la variabilité de ce flux explique la majeure partie de la variabilité journalière de la somme des flux atmosphériques. Appliquées à d'autres glaciers, ces méthodes permettraient de savoir si les conclusions établies pour notre seul glacier d'étude sont valables pour d'autres glaciers. Elles rendraient également possibles la reconstruction du bilan de masse spatialisé sur 10 ans d'autres glaciers et potentiellement une meilleure quantification des processus physiques mis en jeu dans le bilan de masse de ces glaciers tempérés / Albedo is defined as the ratio of reflected to incident radiation over the solar spectrum and is a key parameter in the surface energy balance of snow and ice. This parameter is highly variable both temporally and spatially; thus remote sensing is an ideally suited approach for the retrieval of albedo data.The albedo value depends on both physical properties of the target and the characteristics of the incident radiation. Furthermore, the physical parameters linked with the albedo concept vary in consideration with spectral and angular ranges. Measurements of bi-directional reflectance over natural snow have shown that the Lambertian hypothesis may lead to significant error when estimating albedo from remote sensing data.Detailed knowledge of the angular distribution of radiation reflected by snow allows for the development of a new method to retrieve albedo values for mountainous, snow/ice covered areas. This method takes into account multiple reflections on mountainous areas, anisotropy of radiation reflected by snow and ice, and albedo spectral variations with surface physical properties. The method is applied to visible and near-infrared terrestrial photographs (spatial resolution 10 m) and MODIS data (spatial resolution 250 m). The accuracy of the method is evaluated at ±10% on the retrieved albedo value using concurrent field measurements at theSaint Sorlin Glacier (Grandes Rousses, France) during the summers of 2008 and 2009. The method is used to retrieve albedo data for this glacier from 2000 to 2009. Results indicate that the albedo of the ablation area of the Saint Sorlin Glacier has not shown any decreasing trend over this decade, in opposition to results presented for the Morteratsch Glacier (Switzerland). In addition, the minimal value over the summer period of the whole glacier averaged albedo is highly correlated to the specific annual mass-balance.Albedo data from MODIS and terrestrial photographs are then assimilated into the snow model CROCUS. This assimilation allows for an estimation of the spatialized mass-balance of the Saint Sorlin Glacier over the five studied hydrological years. Root mean square error is evaluated to 0.5 m w.e. For this study, we have used mid-scale meteorological data from SAFRAN. A brief analysis of the contribution from the atmospheric fluxes to the surface energy balance shows that, for the time period considered in this study, the shortwave radiation budget is the main process determining the surface energy balance. Furthermore, variability in shortwave radiation budget explains the major part of the daily variability in surface energy balance.The methods developed in this work are readily applicable to other temperate glaciers. They allows spatialized mass-balance reconstruction on a decadal scale and lead to improved quantification of the physical processes controlling mass-balance in temperate glaciers

L’océan Arctique est marqué par une forte saisonnalité qui se manifeste par la présence d’une banquise permanente dont l’extension varie entre 6 et 15 millions de kilomètres carré. Interface plus ou moins perméable, la banquise limite les échanges atmosphère - océan et affecte le budget énergétique global en réfléchissant une part importante du rayonnement incident. Le manteau neigeux qui se forme à sa surface est un élément essentiel notamment parce qu’il contribue fortement aux propriétés optiques de la banquise. D’une part par son albédo, proche de l’unité dans le visible, qui retarde sensiblement la fonte estivale de la glace. Et d’autre part, il est majoritairement responsable de l’extinction verticale de l’éclairement dans la banquise. Or, la faible intensité lumineuse transmise à la colonne d’eau constitue un facteur limitant important à l’accumulation de biomasse des producteurs primaires souvent des micro-algues, à la base des réseaux trophiques. Le manteau neigeux en surface, par ces propriétés physiques et leurs évolutions temporelles, joue donc un rôle essentiel en impactant directement l’initiation et l’amplitude de la floraison phytoplanctonique printanière. Dans le cadre du réchauffement climatique actuel, les mutations que subit la banquise : amincissement, réduction de son extension estivale et variations des épaisseurs du manteau neigeux bouleversent d’ores et déjà la production primaire arctique à l’échelle globale et régionale.Cette thèse vise à mieux comprendre la contribution du manteau neigeux au transfert radiatif global de la banquise, afin de mieux estimer son impact sur la production primaire arctique. Elle s’appuie sur un jeu de données collecté lors de deux campagnes de mesures sur la banquise en période de fonte. Les propriétés physiques de la neige, SSA et densité, permettent une modélisation précise du transfert radiatif de la neige qui est validée, ensuite, par les propriétés optiques comprenant : albédo, profils verticaux d’éclairement dans le manteau neigeux et transmittance à travers la banquise.Au printemps, la neige marine, marquée par une importante hétérogénéité spatiale, évolue suivant quatre phases distinctes. La fonte, d’abord surfacique puis étendue à toute l’épaisseur du manteau, se caractérise par une baisse de la SSA de 25-60 m2kg-1 à moins de 3 m2kg-1 provoquant une diminution de l’albédo dans le proche infrarouge puis à toute longueur d’onde ainsi qu'une augmentation de l’éclairement transmis à la colonne d’eau. Cette période est chaotique, et marquée par une forte variabilité temporelle des propriétés optiques causées par la succession d’épisodes de fonte et de chutes de neige. Les propriétés physiques de la neige sont utilisées par un modèle de transfert radiatif afin de simuler les profils verticaux d'éclairement, l’albédo et la transmittance de la banquise. La comparaison entre ces simulations et les profils d’éclairement mesurés met en évidence la présence d’impuretés dans la neige dont leurs natures et leurs concentrations sont estimées. En moyenne, la neige échantillonnée contenait 600 ngg-1 de poussières minérales et 10 nng-1 de suies qui réduisaient par deux l’éclairement transmis à la colonne d’eau. Enfin, la modélisation de l’éclairement à toute profondeur de la banquise, représentée de manière innovante par des isolumes, est mise en relation avec l’évolution temporelle de la biomasse dans la glace. Il apparaît que la croissance des algues de glace est systématiquement corrélée avec une augmentation de l’éclairement, et ce, jusqu’à des niveaux d’intensité de l’ordre de 0.4 uEm-2s-2. Ces variations d’éclairement sont causées par le métamorphisme et la fonte de la neige en surface. / The Arctic ocean shows a very strong seasonality trough the permanent presence of sea ice whose extent varies from 6 to 15 millions km2. As an interface, sea ice limits ocean - atmosphere interactions and impacts the global energy budget by reflecting most of the short-wave incoming radiations. The snow cover, at the surface, is a key element contributing to the optical properties of sea ice. Snow enhances further the surface albedo and thus delays the onset of the ice melt. In addition, snow is the main responsible for the vertical light extinction in sea ice. However, after the polar night, this low light transmitted to the water column is a limiting factor for primary production at the base of the oceanic food web. The snow cover, through the temporal evolution of its physical properties, plays a key role controlling the magnitude and the timing of the phytoplanktonic bloom. In the actual global warming context, sea ice undergoes radical changes including summer extent reduction, thinning and shifts in snow thickness, all of which already alter Arctic primary production on a regional and global scale.This PhD thesis aims to better constrain the snow cover contributions to the radiative transfer of sea ice and its impact on Arctic primary production. It is based on a dataset collected during two sampling campaigns on landfast sea ice. Physical properties of snow such as snow specific surface area (SSA) and density allow a precise modeling of the radiative transfer which is then validated by optical measurements including albedo, transmittance through sea ice and vertical profiles of irradiance in the snow.During the melt season, marine snow which shows strong spatial heterogeneity evolves fol- lowing four distinctive phases. The melting, which first appears at the surface and gradually propagates to the entire snowpack, is characterized by a decrease in SSA from 25-60 m2kg-1 to less than 3 m2kg-1 resulting in a decrease in albedo and an increase in sea ice transmittance. This is a chaotic period, where optical properties show a very strong temporal variability induced by alternative episodes of surface melting and snowfalls. The physical properties of snow are used in a radiative transfer model in order to calculate albedo, transmittance through sea ice and vertical profiles of irradiance at all depths. The comparison between these simulations and measured vertical profiles of irradiance in snow highlights the presence of snow absorbing impurities which were subsequently qualitatively and quantitatively studied. In average, impurities were composed of 660 ngg-1 of mineral dust and 10 ngg-1 of black carbon. They were responsible for a two-fold reduction in light transmitted through sea ice. The light extinction, calculated at all depths in sea ice, and represented by isolums, was compared to the temporal evolution of ice algae biomass. The results show that every significant growth in ice algae population is related to an increase of light in the ice. These growths were observed even at very low light intensities of 0.4 uEm-2s-2. Light variations in the ice were linked by snow metamorphism and snow melting at the surface.

O principal objetivo deste estudo foi avaliar a refletância e sua influência no comportamento térmico de tintas refletivas e tintas convencionais aplicadas em telhas de fibrocimento para cobertura de habitações brasileiras. Foram realizados ensaios em laboratório de determinação de cor e de brilho por medida instrumental e determinação da refletância por análise espectrofotométrica em películas. Para o estudo do comportamento térmico foram realizados ensaios de simulação em laboratório com corpos-de-prova expostos à radiação infravermelha emitida por lâmpadas e de exposição à radiação solar em campo através de protótipos com monitorização da temperatura durante as exposições. Os resultados dos ensaios de determinação de cor e de brilho mostraram que as pinturas refletivas e convencionais realmente apresentaram cores correspondentes. Os resultados de refletância mostraram que as pinturas refletivas apresentaram valores de refletância superiores em relação às tintas convencionais, o que foi comprovado pela temperatura medida nos ensaios de exposição à radiação infravermelha e radiação solar. A conclusão do estudo é que as tintas refletivas têm potencial para redução da temperatura superficial da telha de fibrocimento e que é necessária uma continuidade do estudo de durabilidade e do desempenho térmico de tintas refletivas coloridas. / The main purpose of this study was to investigate the effect of reflective colored paints and conventional colored paints applied on fiber cement corrugated roofing sheets, proving whether both type of paints can present different reflection characteristics in the infrared solar radiation and high thermal performance. Color and gloss were measured by instrumental methods and reflectivity (reflection coefficient) was measured using spectrophotometers equipped with integrating spheres in free paint films. In order to investigate the thermal performance of reflective and conventional paints, simulation tests were performed in laboratory by IR lamps using fiber cement specimens and in field by exposure solar radiation using prototypes with temperature monitoring. The results showed that the reflective paints present higher reflectivity and better thermal performance than the conventional paint, independently of the color. The results showed that the reflective paints present potential to reduce superficial temperature of fiber cement corrugated roofing sheets. It is necessary to continue the reflective colored paints study on durability and thermal performance by exposure tests.

Made available in DSpace on 2017-07-21T18:53:02Z (GMT). No. of bitstreams: 1 Flavia Roberta Marenda.pdf: 1506229 bytes, checksum: 7e85c48845e1fc15cca9fa308082955b (MD5) Previous issue date: 2015-02-03 / Conselho Nacional de Desenvolvimento Científico e Tecnológico / The passion fruit industrial use reach only 25% of the total fruit and passion fruit peel, representing 50% of the total, are discarded, but can be used in the extraction of pectin. Recent studies indicate that pectin, modified so as native, has antitumor activity. This study aimed to evaluate the cytotoxicity of pectin of passion fruit peel in tumor cell lines. Extraction has been made and the chemical modification of pectin of passion fruit peel, subjected to three different treatments. Both the raw material and pectin were characterized by specific analyzes. The cytotoxicity of untreated pectins, modified autoclaved and autoclaved were evaluated in tumor lines Jurkat, HeLa and HRT-18. The peel of passion fruit represented 54.7% of total fruit. The passion fruit peel flour bleached untreated and shown to be rich in soluble and insoluble fibers. The flour autoclaved pectin showed higher content of phenolic compounds; however, bleached pectin retained more phenolic compounds from the raw material. The modified pectins had a lower degree of methoxylation and lower molecular weight compared to native pectins, confirming the modification process. The best effect Cytotoxicity in Jurkat cells treated with autoclaved pectin modified with IC50 of 2.63 mg mL-1. The calculation of the selectivity index indicated that the modified autoclaved pectin has a low toxicity to healthy cells. In conclusion, the results demonstrate a potential antitumor promising for autoclaved modified pectin, that needs to be further exploited. / O aproveitamento industrial do maracujá atinge apenas 25% do total do fruto e as cascas do maracujá, que representam 50% desse total, são descartadas, mas podem ser utilizadas na extração de pectina. Estudos recentes indicam que a pectina, tanto nativa quanto modificada, apresenta atividade antitumoral. Assim, este trabalho teve por objetivo avaliar a citotoxicidade de pectinas do albedo do maracujá em linhagens tumorais. Foi feita a extração e a modificação química da pectina do albedo de maracujá, submetido a três diferentes tratamentos. Tanto a matéria-prima quanto a pectina foram caracterizadas por análises específicas. A citotoxicidade das pectinas sem tratamento, autoclavada e autoclavada modificada, foram avaliadas em linhagens tumorais Jurkat, HeLa e HRT-18. A casca do maracujá representou 54,7% do total do fruto. As farinhas do albedo do maracujá sem tratamento e branqueada mostraram-se ricas em fibras solúveis e insolúveis. A farinha e a pectina autoclavada apresentaram maior teor de compostos fenólicos; no entanto, a pectina branqueada reteve mais compostos fenólicos provenientes da matéria prima. As pectinas modificadas apresentaram menor grau de metoxilação e menor massa molar, comparada às pectinas nativas, confirmando o processo de modificação. O melhor efeito de citotoxicidade foi obtido em células Jurkat tratadas com pectina autoclavada modificada, com IC50 de 2,63 mg mL-1. O cálculo do Índice de Seletividade (IS) indicou que que a pectina autoclavada modificada apresenta baixa toxicidade para células saudáveis. Em conclusão, os resultados demonstram promissor potencial antitumoral para a pectina autoclavada modificada, que precisa ser melhor explorado.

Les forêts ont un impact sur le climat mais cet effet est incertain, notamment dans les régions soumises à un climat tempéré. En effet, les processus biogéochimiques et biophysiques caractéristiques des forêts tempérées peuvent avoir un effet soit de refroidissement soit de réchauffement du climat. Une première étape dans l'amélioration de l'évaluation de l'effet climatique des forêts est d'avancer dans la modélisation de l'ensemble de leurs processus biogéochimiques et biophysiques dans les LSM (" Land Surface Model "), utilisés dans les modèles atmosphériques de prévision du temps et du climat. L'albédo de surface est identifié comme une variable clé pour l'étude de l'impact des forêts en termes de forçage radiatif. Pourtant, elle est représentée de façon très simplifiée dans la plupart des LSM, où elle est bien souvent non évolutive. Dans ce contexte, l'objectif de cette thèse est de contribuer à l'amélioration de la représentation de l'albédo de surface dans les LSM. Il s'est agi en particulier d'identifier à partir d'observations satellitaires les variables biophysiques qui pilotent l'albédo de surface des forêts dans l'espace et dans le temps. Un modèle prédictif de l'albédo des forêts aux échelles spatiales considérées par les LSM a été développé. La France métropolitaine a été choisie comme région d'étude et la période allant de 2001 à 2013 a été considérée. Il a été mis en évidence que, sur cette période, 94.4% de la surface occupée par les forêts présente un cycle saisonnier de l'albédo relativement stable d'une année à l'autre. Parmi les 5.6% restants, les changements ont été induits par des modifications soudaines du couvert végétal mais également par un "verdissement" de certaines forêts. Dans le but d'identifier les variables qui pilotent les variations saisonnières de l'albédo de surface des forêts, une nouvelle méthode permettant de désagréger les albédos de surface satellitaires, en albédo du sol nu et de la végétation, a été développée. Les albédos du sol obtenus présentent une dynamique temporelle inter- et intra-annuelle qui est corrélée avec celle de l'humidité superficielle du sol. La variabilité temporelle de l'albédo du sol moyen peut être caractérisée par son écart type, qui est de 0.016. La valeur obtenue par des méthodes pré-existantes est de 0 à 0.004. D'autre part, le cycle saisonnier de l'albédo du sol est cohérent avec le régime des pluies : les valeurs mensuelles moyennes maximales correspondent aux mois les moins pluvieux. C'est vrai dans 68 % des cas, contre 32 % pour l'albédo de surface. Les valeurs moyennes de l'albédo de la végétation (sol) ont été estimées avec une incertitude de 2 % (10 %). Ces albédos désagrégés dynamiques ont permis de construire des cycles annuels moyens. Ces derniers sont utilisés pour forcer le modèle prédictif de l'albédo des forêts fondé sur des variables pouvant être simulées par les LSM. Une validation par rapport à l'albédo de surface satellitaire MODIS a mis en évidence une erreur moyenne de 12% et 8 %, respectivement dans le VIS et dans le NIR (R de 0.63 dans le VIS), soit une amélioration par rapport aux autres méthodes (R de 0.45 dans le VIS). Cette désagrégation de l'albédo de surface a permis de mettre en évidence que l'effet des forêts tempérées sur le bilan d'énergie dépend de la saison, du type de forêt et du type de sol. Il est montré qu'en France métropolitaine, 77.3 % des forêts présentent un bilan radiatif pouvant entraîner un effet de réchauffement durant l'été. Si le verdissement de certaines forêts constaté dans cette thèse devait se généraliser, l'impact radiatif moyen durant l'été pourrait être de 0.187±0.04 W.m-2. La méthode de désagrégation développée durant cette thèse est en cours d'implémentation dans la chaîne opérationnelle du service LSA-SAF d'EUMETSAT. Elle pourra à terme permettre de développer une paramétrisation de ces albédos désagrégés dans les LSM. Cela permettra l'assimilation d'observations de l'albédo de surface dans les LSM. / The forests impact the climate but their effect is uncertain, in particular in the areas with temperate climate. In temperate forests, biogeochemical and biophysical processes can present either a cooling or a warming effect on climate. A first step to improve the evaluation of the climatic effect of forests is to go forward with the modeling of all biogeochemical and biophysical processes in LSMs ("Land Surface Models") used in the atmospheric models used for numerical weather forecast and climate predictions. Surface albedo is identified as a key variable of the impact of forests in terms of radiative forcing. However, surface albedo is represented in a simplified way in LSMs and is, more often than not, non-evolutive. In this context, the objective of this PhD work is to contribute to the improvement of surface albedo modeling in LSMs. A step forward was to identify the biophysical variables which drive the surface albedo of forests in space and time, using satellite observations. A predictive model of the forest albedo was developed considering the spatial resolution used in LSMs. Mainland France was selected as a study area from 2001 to 2013. It was shown that over this period, 94.4% of the forest area presented a relatively stable seasonal albedo cycle, from one year to another. Among the remaining 5.6%, changes in albedo were induced by sudden changes in the vegetation cover, but also in some forests by an increase in greenness. With the aim of identifying the variables which drive the seasonal variations of the surface albedo of forests, a new method was developed to split satellite-derived surface albedo into soil and vegetation albedo values. Soil albedo showed inter- and intra-annual temporal dynamics which are correlated with top soil moisture. The temporal variability of the average soil albedo can be described by its standard deviation, which is of 0.016. In comparison, the values obtained with preexisting methods range from 0 to 0.004. In addition, the seasonal cycle of soil albedo is consistent with the rainfall regime: the yearly maximum average monthly albedo matches the months with less precipitation. This was the case for 68% of forest pixels, against 32% using surface albedo instead of soil albedo. The median values of the vegetation (soil) albedo were estimated with an uncertainty of 2% (10%). These disaggregated albedo values (soil and vegetation) were used to produce average annual cycles. The latter are used to force the predictive model of the forest albedo which is based on LSMs' simulated variables. The validation was conducted using MODIS satellite-derived surface albedo observations. Average error values of 12% and 8% were obtained in the VIS and the NIR spectral domains, respectively (R of 0.63 in the VIS). This is an improvement with respect to pre-existing methods (R of 0.45 in the VIS). Disaggregating surface albedo showed that the effect of temperate forests on the radiative budget depends on season, forest type and soil type. Over mainland France, 77.3% of the forests present a radiative impact which can lead to a warming effect during the summer. If the increase in greenness detected in some forests were to spread to all French forests, the average radiative impact during the summer could be as large as 0.187± 0.04 W.m-2. The disaggregation method developed during this PhD work is under implementation in the operational chain of the EUMETSAT LSA-SAF service. Thanks to this implementation it could be eventually possible to parameterize disaggregated albedo values in LSMs. This will allow the assimilation of surface albedo observations in LSMs.

Atmospheric particulate matter (PM) is linked to various adverse environmental and health impacts. PM in the atmosphere reduces visibility, alters precipitation patterns by acting as cloud condensation nuclei (CCN), and changes the Earth’s radiative balance by absorbing or scattering solar radiation in the atmosphere. The long-range transport of pollutants leads to increase in PM concentrations even in remote locations such as polar regions and mountain ranges. One significant effect of PM on the earth’s climate occurs while light absorbing PM, such as Black Carbon (BC), deposits over snow. In the Arctic, BC deposition on highly reflective surfaces (e.g. glaciers and sea ices) has very intense effects, causing snow to melt more quickly. Thus, characterizing PM sources, identifying long-range transport pathways, and quantifying the climate impacts of PM are crucial in order to inform emission abatement policies for reducing both health and environmental impacts of PM. Chemical transport models provide mathematical tools for better understanding atmospheric system including chemical and particle transport, pollution diffusion, and deposition. The technological and computational advances in the past decades allow higher resolution air quality and weather forecast simulations with more accurate representations of physical and chemical mechanisms of the atmosphere. Due to the significant role of air pollutants on public health and environment, several countries and cities perform air quality forecasts for warning the population about the future air pollution events and taking local preventive measures such as traffic regulations to minimize the impacts of the forecasted episode. However, the costs associated with the complex air quality forecast models especially for simulations with higher resolution simulations make “forecasting” a challenge. This dissertation also focuses on applications, performance analysis, and optimization of meteorology and air quality modeling forecasting models. This dissertation presents several modeling studies with various scales to better understand transport of aerosols from different geographical sources and economic sectors (i.e. transportation, residential, industry, biomass burning, and power) and quantify their climate impacts. The simulations are evaluated using various observations including ground site measurements, field campaigns, and satellite data. The sector-based modeling studies elucidated the importance of various economical sector and geographical regions on global air quality and the climatic impacts associated with BC. This dissertation provides the policy makers with some implications to inform emission mitigation policies in order to target source sectors and regions with highest impacts. Furthermore, advances were made to better understand the impacts of light absorbing particles on climate and surface albedo. Finally, for improving the modeling speed, the performances of the models are analyzed, and optimizations were proposed for improving the computational efficiencies of the models. Theses optimizations show a significant improvement in the performance of Weather Research and Forecasting (WRF) and WRF-Chem models. The modified codes were validated and incorporated back into the WRF source code to benefit all WRF users. Although weather and air quality models are shown to be an excellent means for forecasting applications both for local and hemispheric scale, further studies are needed to optimize the models and improve the performance of the simulations.

Diese Dissertation ist innerhalb eines Teilprojekts des Schwerpunktprogramms SPP1233 ”Megacities Megachallenge - Informal Dynamics of Global Change“ entstanden. Thema der vorliegenden Arbeit ist die Untersuchung der heterogenen Reflexion der Sonnenstrahlung an urbanen Bodenoberflächen, sowie deren Einfluss auf die Bestimmung der optischen Dicke von Aerosolpartikeln aus Satellitendaten. Zu diesem Zweck wurden flugzeuggetragene Messungen der spektral aufgelösten, reflektierten solaren Strahlung durchgeführt. In dieser Arbeit werden Messungen mit dem SMART-Albedometer (Spectral Modular Airborne Radiation measurement sysTem) präsentiert, die im Rahmen zweier Messkampagnen in Leipzig im September 2007 und in Zhongshan, China im Dezember 2009 erfasst wurden. Die spektrale Bodenreflektivität und Bodenalbedo wurden aus den spektralen Messungen der aufwärtsgerichteten Stahldichte (Radianz) und Strahlungsflussdichte (Irradianz) bestimmt. Dazu wurden eindimensionale Strahlungsübertragungsrechnungen durchgeführt. Der Einfluss der Flughöhe auf die Bodenreflektivität und Bodenalbedo wird anhand eines Messbeispiels, sowie einer Modellstudie mit ein- und dreidimensionalen Strahlungsübertragungsrechnungen diskutiert. Für beide Untersuchungsgebiete, Leipzig und Zhongshan, wird die Heterogenität der Reflexion solarer Strahlung an urbanen Oberflächen gezeigt. Der Einfluss der im operationellen Aerosolalgorithmus des satellitengetragenen Instrumentes MODIS (MODerate resolution Imaging Spectroradiometer) getroffenen Annahmen zur Bodenreflektivität auf die optische Dicke von Aerosolpartikeln, wurde mittels der gemessenen spektralen Bodenreflektivität und einer auf Strahlungsübertragungsrechnungen basierenden Modellstudie quantifiziert. Ein linearer Zusammenhang zwischen Bodenreflektivität und optischer Dicke von Aerosolpartikeln wird für beide Fallbeispiele gezeigt. Mittels der Messungen in Zhongshan kann bestätigt werden, dass die Bodenreflektivität für urbane Oberflächen im Aerosolalgorithmus unterschätzt wird. Im Rahmen der Modellstudie wird die Sensitivität des Aerosolalgorithmus auf die programminternen Annahmen zur Bodenreflektivität quantifiziert.

Uncertainty of predicted change in precipitation frequency and intensity motivates the scientific community to better understand, quantify, and model the possible outcome of dryland ecosystems. In pulse dependent ecosystems (i.e. monsoon driven) soil moisture is tightly linked to atmospheric processes. Here, I analyze three overarching questions; Q1) How does soil moisture presence or absence in a shallow or deep layer influence the surface energy budget and planetary boundary layer characteristics?, Q2) What is the role of vegetation on ecosystem albedo in the presence or absence of deep soil moisture?, Q3) Can we develop empirical relationships between soil moisture and the planetary boundary layer height to help evaluate the role of future precipitation changes in land surface atmosphere interactions?. To address these questions I use a conceptual framework based on the presence or absence of soil moisture in a shallow or deep layer. I define these layers by using root profiles and establish soil moisture thresholds for each layer using four years of observations from the Santa Rita Creosote Ameriflux site. Soil moisture drydown curves were used to establish the shallow layer threshold in the shallow layer, while NEE (Net Ecosystem Exchange of carbon dioxide) was used to define the deep soil moisture threshold. Four cases were generated using these thresholds: Case 1, dry shallow layer and dry deep layer; Case 2, wet shallow layer and dry deep layer; Case 3, wet shallow layer and wet deep layer, and Case 4 dry shallow and wet deep layer. Using this framework, I related data from the Ameriflux site SRC (Santa Rita Creosote) from 2008 to 2012 and from atmospheric soundings from the nearby Tucson Airport; conducted field campaigns during 2011 and 2012 to measure albedo from individual bare and canopy patches that were then evaluated in a grid to estimate the influence of deep moisture on albedo via vegetation cover change; and evaluated the potential of using a two-layer bucket model and empirical relationships to evaluate the link between deep soil moisture and the planetary boundary layer height under changing precipitation regime. My results indicate that (1) the presence or absence of water in two layers plays a role in surface energy dynamics, (2) soil moisture presence in the deep layer is linked with decreased ecosystem albedo and planetary boundary layer height, (3) deep moisture sustains vegetation greenness and decreases albedo, and (4) empirical relationships are useful in modeling planetary boundary layer height from dryland ecosystems. Based on these results we argue that deep soil moisture plays an important role in land surface-atmosphere interactions.