Recently, commercial softwares for PV system simulation released bifacial extensions. While research laboratories have developed their own simulation tools, in both cases it is imperative to display their applicability, as well as continuously assess their accuracy and/or limitations in practice, i.e. for different bifacial PV systems and field conditions. This paper presents a design and energy yield simulation study of two bifacial PV systems installed and operating in Nordic climate conditions, i.e. in Vestby, Norway ( System 1) and in Halmstad, Sweden (System 2). The aim of this study is: • To validate and compare the accuracy of two bifacial PV simulation tools newly featured in the software platforms of PVsyst and Polysun respectively, against real-field energy yield data. Each investigated system is modeled and analyzed with both simulation tools, resulting in four individual case stu dies. Further details on the systems’ monitoring set-up, the data input, modeling steps, and the involved uncertainties are presented in this paper. The results of the four case studies show higher percent deviations (both monthly and hourly data) between simulated energy results and real energy results during winter periods compared to summer periods. System 1 had a lower bifacial gain (around 2%) than System 2 which ranges from 2% in summer periods to 25% during winter. The collected field data had too high of an uncertainty to determine whether the bifacial PV simulation extensions are accurate within a certain tolerance. The reason for higher simulation inaccuracy in the winter is due to: lower production, higher uncertainty in albedo, and more diffuse irradiation. It is recommended for the bifacial PV simulation extensions include options for considering a variable albedo. The bifacial gain in System 2 was higher in the winter because of the higher albedo value given whereas in System 1, the albedo value was kept constant. Further parametric studies should be conducted on the bifacial gain using vertical mounted bifacial PV modules oriented east and west for Nordic climate conditions.

L'objectif de la thèse est de développer un albédo de surface journalier pronostique dans les modèles météorologiques et d’évaluer son impact pour le bilan d'énergie et l'hydrologie dans la plate-forme de modélisation SURFEX sur le domaine France. En premier lieu, un albédo climatologique est à ce jour considéré dans SURFEX. Il est analysé dans cette étude par rapport aux albédos quotidiens de SEVIRI et MODIS dont ce dernier est obtenu à partir d'une méthode originale que l'on valide. Ensuite, une méthode est développée pour obtenir des albédos du sol et de la végétation de façon séparée à la fois statiquement, donc sur une base climatologique, puis dynamiquement en s'appuyant sur plusieurs années de données du satellite MODIS. Une fois réglé l'albédo du sol journalier, il est recherché une calibration avec l'humidité du sol nu à l'aide des données du réseau de stations sol SMOSMANIA du sud-ouest de la France. Il est montré que l'on peut prédire l'évolution de l'albédo de surface, par comparaison avec les observations spatiales avec l'humidité seule dans la limite d'une végétation faiblement couvrante. Cet albédo simulé est complété par celui de la végétation seule à partir d'une paramétrisation simplifiée du code de transfert radiatif PROSAIL. L'approche théorique est validée avec les données du site de Majadas pour lequel on montre que l'on sait simuler le cycle d'évolution de l'albédo total avec prise en compte de la chlorophylle au niveau de la feuille. En dernier lieu, il a été réalisé une étude d'impact du nouveau albédo évolutif sur le bilan d'énergie et l'hydrologie dans SURFEX sur la France. Il est aussi mis en place une assimilation de l'albédo conjointement avec l'indice foliaire et l'humidité superficielle, ce qui a des effets positifs pour le cas des végétations qui ne sont pas trop denses. / The main objective of the thesis is to develop a prognostic surface albedo of the visible spectrum and near infrared and assess its impact on the energy balance and hydrology in the modelling platform of SURFEX. First, a statistical approach has generated a global climate albedo product at 0.05 ° for bare soil and vegetation using multiple years 8 -day MODIS onboard TERRA and AQUA satellites heliosynchronous data. Then, an original method has been developed to reduce temporal resolution of MODIS 500m albedo to daily. The result is validated against in situ measurements as well as daily albedo from geostationary satellite MSG / SEVIRI Land SAF project after projection of MODIS. Then a method of separating albedo of bare soil and vegetation is applied to the datasets of the two satellite systems. Using a threshold of vegetation cover, a calibration of the albedo bare soil with measured soil moisture is derived from 2007 to 2010 for 12 SMOSMANIA stations over southwestern France. We derived a parameterization of the albedo of bare soil with moisture to make the climate changing albedo. The albedo and simulated happens to be very well correlated with observations from space, which helps to explain the albedo variations at very short notice. To change seasonally albedo, a simple parameterization of canopy albedo derived from detailed radiative transfer code PROSAIL is used. The variables are the albedo of the sheet, canopy geometry and chlorophyll content. In order to be sensitive to chlorophyll, the study is based on an albedo at 560 nm. The theoretical approach is validated with MODIS satellite data for the site Majadas (Spain). The next step is to conduct an impact study of this new predictive albedo on the energy balance and hydrology within SURFEX over France and highlighting effects on temperature. More preliminary restricted to a SMOSMANIA station, an assimilation scheme is developed for surface albedo together with the leaf area index LAI and surface moisture. This effects an improvement in the prescribed LAI at the beginning of crop growth.

The Pliocene, a geologic epoch spanning ~2.6-5.3 million years ago (Ma), was a period in Earth’s history where temperatures were several degrees warmer than today and atmospheric CO2 was close to modern levels, making it an analogue for future climate change. Following this interval, the planet’s climate shifted to the familiar glacial-interglacial cycles of the Pleistocene (~0-2.6 Ma), beginning with the development of extensive Northern Hemisphere ice sheets at ~2.7 Ma. In response to these changes through the Plio-Pleistocene, several components of the Earth System, particularly related to East Asia and the North Pacific Ocean, varied both temporally and spatially, further modifying regional and global climate through various feedbacks. In this thesis, I utilize a combination of geochemical proxies derived from North Pacific marine sediments as well as a regional climate model to better understand the evolution of the westerly winds, North Pacific Ocean circulation, and East Asian desert landscapes, across the last five million years. In Chapter 1, I reconstruct Pliocene dust fluxes at two different sites in the North Pacific using the constant flux proxy extraterrestrial 3He (3HeET), the first of such records in the Pliocene. Along with 3HeET-derived export productivity fluxes and sea surface temperatures from the westernmost core, I show that the Northern Hemisphere westerly winds, were shifted poleward and weaker during much of the warm Pliocene. Coinciding with the intensification of Northern Hemisphere Glaciation, the westerlies shifted equatorward and strengthened at ~2.7 Ma, and during subsequent glacial periods thereafter. Combining my dust flux record with others from different ocean basin, I find that these changes in the westerly winds were globally synchronous. Chapter 2, entitled “Pliocene Variability of Active Pacific Meridional Overturning Circulation: Reevaluating North Pacific Productivity and Redox Conditions from ~2.5-6 Ma”, presents additional 3HeET-based export productivity flux data, as well as redox element concentrations, from the central subarctic North Pacific through the Pliocene. The new records suggest elevated North Pacific export production during the interval spanning ~4-5.5 Ma, followed by a decrease in the mid-Pliocene (~3.5-4 Ma). Combining this new data with previously published records and modeling output, I provide additional evidence for an active Pacific meridional overturning circulation during the warmer-than-present Pliocene, and add constraints on its variability under various climatic conditions. In Chapter 3, I bring together two constant flux proxy-derived dust flux datasets from the same core in the western North Pacific Ocean to provide novel insight into Quaternary dust dynamics in East Asia. By utilizing constant flux proxies, and accounting for inputs of volcanic material, I show for the first time that dust input to the North Pacific decreased over the last ~2.7 Myr, particularly during glacial periods. While quite different from other previously published dust datasets, this finding is consistent with our current understanding of East Asian dust production mechanisms, and acts as a strong impetus to perform more comprehensive studies of dust fluxes to the North Pacific and other depositional areas downwind of arid regions. Chapter 4 transitions to a terrestrial setting, in which I investigate the impacts of shifting arid region surface albedo on the atmospheric boundary layer using the Hami Basin, China, as a test location. Combining new simulations from the Weather Research and Forecasting base model and available geologic data, I report a previously undescribed “wind-albedo-wind” feedback process. Specifically, I propose that wind erosion, in conjunction with surficial sediments of various albedos, leads to altered wind speeds, and eventually fluctuations in erosion itself. In Chapter 5, I expand upon the work in the preceding chapter by coupling the Weather Research and Forecasting model with a chemistry component to simulate dust emissions. In addition, along with albedo, I characterize previously interpreted surface changes through time to reflect shifts in erodibility and surface roughness. I conclude that although albedo does ultimately influence near-surface wind speeds and dust emissions as predicted in my earlier study, the effects of variable surface roughness and erodibility dominate. Integrating these results with an updated interpretation of the geologic evolution of the Hami Basin, we find that during various periods of the last ~700 ky, the Hami Basin, and likely the greater stony Gobi Desert, could have been much more important dust sources than today.

Antropogen inverkan på växthuseffekten är en bidragande faktor i den globala uppvärmningen, som i sin tur kommer att förstärka värmeböljor och den urbana värmeöeffekten. Kombinationen av dessa fenomen kan ha förödande konsekvenser. Höga temperaturer medför en minskad komfort för städers invånare och risken för värmerelaterad sjukdom och dödlighet ökar. Geoengineering som höjer det urbana albedot är en möjlig metod för att motverka allt mer intensiva värmeböljor, vilket i denna studie appliceras på Uppsala stad i form av vita tak. Den totala arean av mörka tak i Uppsala uppgår till 2,8 · 106 m2, vilket utgör mer än en tredjedel av Uppsalas totala takyta. Denna studie visar att implementeringen av vit plåt på mörka tak kan öka takets albedo med 0,42 vilket innebär att det finns en stor potential att öka det urbana albedot i Uppsala. Tidigare forskning tyder på ett samband mellan en ökning av det urbana albedot och en minskad medeltemperatur i städer. Det är därför rimligt att anta att en storskalig implementering av denna typ av geoengineering i Uppsala skulle kunna lindra effekterna av framtida värmeböljor.

This study aims to develop a simulation and optimisation tool for bifacial photovoltaic (PV) modules based on the open-source code OptiCE and evaluate dynamic and static albedo impact on a bifacial PV system. Further, a review of the market price development of bifacial PVs' and an optimisation to maximise energy output was conducted. Two case studies with bifacial PV modules, a single-axis tracker in Denver, USA, and a vertical and a tilted system installed at a farm outside Västerås, Sweden, were analysed in this study. The results showed that an hourly dynamic albedo value could provide more accurate simulation results of the rear side irradiance for the bifacial single-axis tracker than a static albedo value. The developed model showed an R2 accuracy of 93% and 91% for the front and rear sides, respectively, when simulated with an hourly albedo value for the bifacial single-axis tracker system. The optimisation was based on weather data from 2020. The results showed that the tilted reference system could increase its energy output by 8.5% by adjusting its tilt from 30° to 54° and its azimuth angle from 0 to -39°. In contrast, the vertical system would increase its energy output by 2.1% by rotating the azimuth angle from -90° to -66°. Conclusions that could be drawn are that bifacial PV price has closed in on the high-performance monofacial PV price the last five years and may continue to decrease in the coming years. Further, it was concluded that detailed dynamic albedo values lead to more accurate simulations of the ground-reflected irradiance. The availability of measured albedo data at the location is essential when the ground-reflected irradiance stands for a significant share of the irradiance. It was determined that during 2020 the optimal configurations of a vertical and tilted bifacial PV system in Västerås would save 11 300 SEK by consuming self-produced electricity and earn 11 600 SEK from selling the surplus of electricity for the farm outside Västerås.

The amount of light an exoplanet reflects and emits towards an observer waxes and wanes as the planet orbits through its phases. The amplitude and profile of reflection phase curves constrain the albedo of planetary surfaces and atmospheres, while the thermal amplitude and profile reveal temperature distributions and heat transport efficiencies, all providing valuable insight into the nature of exoplanet surfaces and atmospheres. In this dissertation I highlight the usefulness of utilizing full orbital phase curves in addition to occultation measurements, which provides a higher sensitivity to planetary photons at the expense of a more challenging data reduction. In the first few chapters of this dissertation, I introduce a novel non-parametric algorithm to produce clean, robust exoplanet phase curves, and apply it to separate ensembles of 115 Neptunian and 50 Terran exoplanets observed by the Kepler satellite to measure an upper limit on the average albedo of Kepler’s Neptunian planets, and make the first constraint on the average albedo of Terran worlds. In the fourth chapter, I present the full orbital phase curve and occultation of the ultra-hot Jupiter WASP-100b observed by the Transiting Exoplanet Survey Satellite (TESS), and with the use of Bayesian methods, present the first measurement of a phase shift of the thermal maximum among the phase curves observed by TESS, the degree of which challenges the predicted efficiency of heat transport in the atmospheres of ultra-hot Jupiters. In the final chapter, I present an example of how the NASA ROCKE-3D general circulation model can be used to explore the physical mechanisms that influence the habitability of terrestrial exoplanets, and then show how I generated phase curves from the 3-dimensional models to study the signals produced by simulated TRAPPIST-1 habitable-zone worlds. The work in this dissertation contributes valuable new information to the astronomical literature and provides avenues for further research on the nature of short-period exoplanets.

Spectral reflectivity and albedo are obtained from airborne measurements of spectral irradiance and radiance during two field campaigns in Leipzig, Germany and Zhongshan, China. The data measured above urban and rural areas have been investigated with respect to the heterogeneity and anisotropy of the surface. Furthermore the spectral albedo and reflectivity measured above the same surface but at different flight altitudes have been analyzed. These data is used to estimate the impact of multiple scattering processes by aerosol particles and gas molecules.

The Arctic climate has changed significantly in the last decades, experiencing a dramatic loss of sea ice and stronger than global warming. The Arctic surface temperature and the growth or melt of sea ice is determined by the local surface energy budget. In this context, clouds are of essential importance as they strongly interact with the radiative fluxes and modulate the surface energy budget depending on their properties, the surface types, and atmospheric thermodynamics. For the quantification of changes in the radiative energy budget (REB) associated with the presence or absence of clouds, the concept of cloud radiative forcing (CRF) is commonly used. This concept is defined as the differences between the REB in cloudy and cloud-free conditions, two atmospheric states which can not be observed at the same location and time. Consequently, either radiative transfer simulations or observations in both states have to be related, both of which complicate the derivation of CRF. A review of available studies and their approaches to derive the CRF reveals conceptual differences as well as deficiencies in the handling of radiative processes related to the surface albedo. These findings call into question the current state of CRF assessment in the Arctic based on the few available studies, but also their comparability. By combining atmospheric radiative transfer simulations with a snow albedo model, two processes that control the surface albedo during the transition from cloud-free to cloudy conditions and their role in the derivation of CRF are discussed. The broadband surface albedo of snow surfaces typically increases in the presence of clouds due to a spectral weighting of downward irradiance toward shorter wavelengths. For more absorbing surface types such as white ice and melt ponds, which are common in summer, there is a strong shift between the albedo of direct and diffuse illuminated surface, which diminishes the surface albedo depending on the cloud optical thickness and solar zenith angle. In this thesis, a hypothesis on the impact of those surface-albedo--cloud interactions on the annual cycle of shortwave CRF is discussed, but an application to inner Arctic conditions remains an open issue. An improved method to derive the shortwave CRF is proposed and an application to two airborne campaigns in the marginal sea ice zone northwest of Svalbard (Norway) illustrates the role of surface-albedo--cloud interactions in the Arctic in spring and early summer. For the longwave CRF, conceptual differences and the general interpretation of the different CRF estimates are discussed and illustrated for a case study. Radiative transfer simulations of a rarely observed annual cycle of thermodynamic profiles in the inner Arctic are used to study both longwave CRF approaches and the impact of thermodynamic profiles on the longwave CRF. Making use of airborne low-level flights in the MIZ and other available datasets, common seasonal radiative states on sea ice and case studies of warm air intrusions and cold air outbreaks are illustrated. The CRF is analyzed as a function of the observed cloud/surface regime, which is extended by radiative transfer simulations characterizing the conditions in this region and seasons.

The surface albedo significantly modulates the atmospheric energy budget and, thus, vertical radiation, energy, and mass fluxes. Therefore, it regulates the local and regional effects of climate warming. Over a forest canopy, the surface albedo mainly depends on the seasonal leaf state. Furthermore, for certain surface types, such as snow, it has been shown that the surface albedo changes as a function of cloudiness. A similar effect is expected over forest surfaces, leading to complex feedback loops between forest surfaces and climate. To investigate these processes, a pilot study was performed at the Leipzig floodplain crane to observe the forest canopy albedo under different atmospheric conditions in 2021. First analyses revealed a dependency of the forest albedo from the cloud state, which is slightly stronger in the near-infrared wavelength range compared to the visible wavelength range. / Der atmosphärische Strahlungshaushalt und damit auch die vertikale Strahlungsverteilung, Energie- und Massenflüsse werden signifikant durch die Bodenalbedo gesteuert. Diese regulieren somit lokale und regionale Effekte der Klimaerwärmung. Über einem Wald hängt die Bodenalbedo hauptsächlich vom saisonalen Blattstatus ab. Zudem wurde für bestimmte Bodentypen wie Schneeoberflächen gezeigt, dass die Bodenalbedo eine Funktion der Bewölkung ist. Ähnlicher Effekte werden für Waldoberflächen erwartet, welche zu komplexen Rückkopplungseffekten zwischenWaldoberflächen und dem Klima führen. Um diese Prozesse zu untersuchen wurde im Jahr 2021 eine Vorstudie am Leipziger Auwaldkran durchgeführt, um die Waldalbedo unter verschiedenen atmosphärischen Bedingungen zu beobachten. Erste Analysen zeigen, dass auch die Albedo des Waldes von den Bewölkungsbedingungen abhängt. Der Effekt ist dabei etwas stärker im nah-infrarotem als im sichtbaren Wellenlängenbereich zu beobachten.

Mars is a potentially habitable planet given the appropriate planetary engineering efforts. In order to create a habitable environment, the planet must be terraformed, creating quasi-Earth conditions. Benchmarks for minimum acceptable survivable human conditions were set by observing atmospheric pressures and temperatures here on Earth that humans are known to exist in. By observing a positive feedback reaction, it is shown how the sublimation of the volatile southern polar ice cap on Mars can increase global temperatures and pressures to the benchmarks set for minimum acceptable survivable human conditions. Given the degree of uncertainty, utilization of pressure scale heights and the Martin extreme terrain were used to show how less than desirable conditions can still produce results where these benchmarks can be met. Methods for obtaining enough energy to sublimate the southern polar ice cap were reviewed in detail. A new method of using dark, carbonaceous Martian moon material to alter the overall average albedo of the polar ice cap is proposed. Such a method would increase Martian energy efficiency. It is shown that by covering roughly 10% of the Martian polar ice cap with dark carbonaceous material, this required energy can be obtained. Overall contributions include utilization of pressure scale heights at various suggested settlement sites, as well as polar albedo altering as a method of planetary engineering. This project serves as a foundational work for long term solar system exploration and settlement.