1,720,957 research outputs found
Direct measurements of light absorbing particles impacts and ice nucleation activity in Svítnafelljökull
No full textMeasurements of black carbon and its impact over Vatnajökull Ice Cap in southeast Iceland on 2018
No full textSurface snow measurements of black carbon (BC) were carried out in the spring of 2018 at Svínafelljökull, an outlet glacier of the Vatnajökull Ice Cap (VIC) in southeast Iceland. The average annual rate of mass change of VIC (-1.34± 0.12 m w.e. a−1), during the period of 2002-2010, is among the highest mass loss rates globally in the 21st century. The Svínafelljökull has retreated 800m and lost 30% of its 1890 volume. Light-absorbing particles, such as black carbon (BC), dust and brown carbon (BrC), alter the snow melt and optical properties. This impact on snow reflectivity decline can be a major contributor to the regional accelerated melting seen in recent years. Current atmospheric models potentially underestimate the presence of light absorbing aerosols (LAA) in the Arctic region. Direct measurements of LAA, specifically BC, are very scarce. Three surface sites were selected for collecting snow surface samples and mobile albedo measurements. Our focus is to investigate how much of the observed change in snowmelt in southeast Iceland can be attributed to the deposition of LAA, such as BC, using the Snow, Ice, and Aerosol Radiative (SNICAR) model. Results from BC mass concentration distribution using the Single Particle Soot Photometer (SP2) will be discussed
Light absorbing particles in the cryosphere: occurrence, impacts, and participatory decision-making
No full textThe cryosphere consists of the frozen water and permafrost in the earth system. As a result of the current climate crisis, the cryosphere is undergoing major changes. The Arctic, containing important features of the cryosphere, is the fastest warming region in the world. Arctic glaciers and the Greenland Ice Sheet have started to experience an increase in mass loss rates leading to enhanced sea level rise contribution. Continued sea level rise through the 21st century will have wide-reaching impacts on the livelihoods of millions of people, especially those living in low-lying coastal areas. Understanding the different drivers of physical change in the Arctic is therefore important to accurately predict future climate conditions and identify effective climate justice policies. The Arctic mass loss is driven by temperature, albedo perturbations, and cloud cover and feedbacks. Some of the Arctic albedo change drivers are light absorbing particles (LAP), which include black carbon (BC), brown carbon (BrC), mineral dust, volcanic ash, and snow algae. However, observations of occurrence, sources, and magnitude of impacts of LAP across the cryosphere system remain scarce. Additionally, understanding the way LAP drive albedo changes is also underdeveloped. LAP radiative forcing is controlled by complex interactions and feedbacks over the Earth system that affect snow and cloud microphysics. This thesis expands the understanding of the LAP feedbacks and interactions in the cryosphere. The first part of this thesis characterizes LAP occurrence and its influence on snow albedo through the combined effect of surface darkening and snow metamorphism. Here, I find that LAP snow-aging feedback results in albedo reductions 3-8 times larger than previous studies associated with LAP alone have shown. In the second part, this thesis evaluates the connection between LAP and total particulate ability to enable the formation of ice crystals in clouds, or ice nucleation activity (INA). Although the glaciation in mixed-phase clouds, which represent more than half of Arctic clouds, are influenced by various parameters (temperature, updraft velocity, etc.) ice nuclei play a critical role in enabling their formation. As each particle has different INA, mixed-phased clouds are influenced both by particle availability and characteristics of the aerosol. As dust is believed to be the most important type of ice nuclei and Iceland is the main source of high latitudes dust transport, we investigate LAP INA in Iceland. I find that methanol-soluble organic aerosols have a more important role in INA than BC or high latitude dust. Furthermore, BC and dust, can potentially inhibit methanol-soluble organic aerosol INA and therefor impact precipitation patterns. This also means methanol-soluble organic aerosol internal snow mixing must also be quantified and further characterized to fully constrain LAP effects on snow albedo. The third part of this thesis focuses on LAP trends in the Arctic and their potential sources by analyzing LAP, major ions, and trace elements over the past 25 years. I analyze the snow chemistry observed in Greenland using both snow measurements and analysis of a shallow ice core. My results indicate dust and long-range transport are important aerosol sources in the Arctic. The combination of these three studies in this thesis contribute to our understanding of LAP impacts over the Arctic, specifically the Greenland ice sheet and Iceland glaciers. These studies can help improve climate models regional projections by providing better parameterizations of LAP feedbacks and snow chemistry. Understanding the impacts and some of the potential sources of LAP can pave the way for establishing mitigation policies for Short lived climate forcers (SLCF), which includes LAP. However, we must ensure that those policies are transformational and just. To this end, this dissertation provides a framework for participatory decision-making to better equip those tasked with designing and implementing climate public policy. Transformative and just mitigation policies depend on informed and active citizenship, this is the spirit of Action for Climate Empowerment (ACE), Art 12 of the Paris Agreement. Here, we developed and proved a novel approach, combining backcasting and Talanoa dialogue, to facilitate widespread buy-in from key stakeholders while fostering justice in climate change policy making. National ACE strategies that ensures informed participation in decision making, underpins all climate action will enable and catalyze climate action on all fronts – everything, everywhere all at once.Ph.D.Includes bibliographical reference
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
- …
