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Isotopic composition of the atmospheric water vapor during the austral summer at Concordia Station, Dome C, East Antarctica (December 2023 – February 2024)
No full textThe dataset provides a 2.5-month record (December 6th 2023 – February 14th 2024) of the atmospheric water vapor isotopic composition at Concordia Station (Dome C), East Antarctica (-75.10°N, 123.35°E, 3233 m a.s.l.). The atmospheric water vapor isotopic composition is measured by two different laser spectrometers: a L2130-i analyser, manufactured by PICARRO Inc. (CRDS measurement technique) and a prototype version of the ProCeas H2O analyser, manufactured by AP2E Inc. (OF-CEAS measurement technique). The inlet of the instrumental set-up is sampling the atmosphere from 50 cm above the snow surface. The dataset provides the hourly-averaged calibrated measurements from both laser spectrometers. The datetime column is in UTC (UTC+8 for local datetime). The timestamp represents the start of the hourly-averaged period. The humidity (mixing ratio) data has been calibrated against an independent humidity measurement and is reported in ppmv. The isotope data has been calibrated for the isotope-humidity dependency and against the VSMOW-SLAP scale and is reported in delta-notation (in ‰)
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe 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
Get PDF“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
Get PDFWe 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
Get PDFWe 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
Impact of Surface Processes on the Antarctic Water Isotope Climate Signal
No full textStabile vannisotopregistre i polare iskjernene gir unik informasjon om tidligere klimavariasjoner. Deres nøyaktige tolkning avhenger imidlertid av forståelsen av prosessene som danner isotopsignalet i snøen, som senere blir omdannet til is. Det ble tidligere antatt at nedbørssignalet, som bærer integrert klimainformasjon om vannets kretsløp, ble bevart etter snøfall, men nyere studier har vist at overflateprosesser er viktige for dannelsen av isotopsignalet. Denne avhandlingen undersøker virkningen av disse prosessene på det sesongmessige til flerårige isotopsignalet ved Dome C, et lavakkumulasjonssted på den antarktiske iskappen.
Artikkel I fokuserer på hvordan post-deposisjonsprosesser påvirker isotopsignalet til snøoverflaten. Ved å bruke parallelle in-situ observasjoner av snøen og nedbøren kvantifiserer vi den gjennomsnittlige endringen av snøens isotopsammensetning. Vi viser at snøoverflaten i gjennomsnitt er beriket i δ18O og δD og sammen med en lavere andreordensparameter deuterium-excess (d-excess) sammenlignet med nedbøren. Ved å estimere flukser av overflatefuktighet fra meteorologiske observasjoner, viser vi en sterk sesongvariasjon i flukser, hvor sublimering dominerer om sommeren og kondensasjon om vinteren er minimal. Dette resulterer i et netto årlig massetap, som indikerer at damputveksling må bidra betydelig til den gjennomsnittlige endringen av isotopsignalet. Disse funnene gir den første observasjonsbaserte kvantifiseringen av den gjennomsnittlige endringen av snøens isotopsignal ved overflateprosesser på årlige tidsskalaer.
Artikkel II presenterer nye observasjoner av isotopsammensetningen til vanndamp i atmosfæren, en avgjørende parameter for isotoputvekslingen mellom snøoverflaten og atmosfæren. Ved å bruke to uavhengige laserspektrometre installert parallelt ved Dome C,
en veletablert Picarro-analysator og en prototype av et nytt laserspektrometer utviklet for lavfuktighetsmiljøer, dokumenterer vi den atmosfæriske vanndampens δ18O, δD og d-excess over en hel 2,5-måneders sommersesong. Verdiene fra de to instrumentene stemmer godt overens, som gir tillit til nøyaktigheten og påliteligheten av målingene. Disse observasjonene er verdifulle for å evaluere og forbedre isotopaktiverte generelle sirkulasjonsmodeller, som demonstrert av vår vurdering av LMDZisos evne til å registrere gjennomsnittet og døgnsyklusen av isotopsammensetningen til vanndamp i atmosfæren.
Artikkel III integrerer kunnskapen og observasjonsdatasettene fra de to foregående studiene i en modelleringsstudie for å undersøke virkningen av overflateprosesser på isotopsignalet over forskjellige tidsskalaer. Ved å bruke en tilpasset versjon av SNOWISOmodellen for lavakkumulasjonssteder identifiserer vi først at sesongvariasjonen i isotopsignalet observert i snøoverflaten kan forklares ved den kombinerte effekten av isotopfraksjonering under damputveksling og den kontinuerlige blandingen av fersk nedbør med eldre snø. Inkludering av isotopisk fraksjonering under damputveksling forbedrer også betydelig representasjonen av den observerte sesongamplituden og den månedlige gjennomsnittsvariabiliteten i snøoverflatens isotopsammensetning. Vi viser videre at damputveksling endrer både gjennomsnittet og variasjonen av flerårige isotopregistre ved å berikegjennomsnittet av δ18O mens det reduserer den årlige variasjonen og reduserer gjennomsnittet av d-excess mens det øker den årlige variasjonen. Ved å teste forskjellige nedbørskonfigurasjoner, viser vi at nedbørens intermittens påvirker størrelsen på effekten av isotopisk damputveksling på de isotopiske registreringene.
Til sammen bidrar de tre artiklene med en omfattende og kvantitativ analyse av overflateprosesser som påvirker isotopsignalene i snøoverflaten og dypere i snøpakken ved Dome C. Funnene i denne avhandlingen fremmer forståelsen av isotopsignaldannelsen ved iskjernens overflate, noe som vil bidra til å forbedre den tolkningen av iskjerneregistre.Stable water isotope records in polar ice cores provide unique information on past climatic variations. However, their accurate interpretation relies on understanding the processes forming the isotopic signal in the snow, later transformed into ice. It was previously assumed that the precipitation signal, carrying integrated climatic information of the hydrological cycle, was preserved after snowfall. Yet, recent studies have highlighted the importance of surface processes for the isotopic signal’s formation. This thesis investigates the impact of these processes on the seasonal to multi-decadal isotopic signal at Dome C, a low-accumulation site on the Antarctic ice sheet.
Paper I focuses on how post-depositional processes impact the isotopic signal of the snow surface. Using parallel in-situ observations of the snow and the precipitation, we quantify the average alteration of the snow isotopic composition and show that, the snow surface is enriched in δ18O and δD, together with a lower second order parameter deuterium-excess (d-excess), compared to precipitation. By estimating surface moisture fluxes from meteorological observations, we show a strong seasonality of fluxes, where sublimation dominates in summer while condensation during the winter is minimal. This results in a net annual mass loss, and indicates that isotopic fractionation during vapor exchange must significantly contribute to the mean alteration of the isotopic signal. These findings provide the first observational quantification of the mean alteration of the snow isotopic signal by surface processes on annual time scales.
Paper II provides novel observations of the atmospheric water vapor isotopic composition, a crucial parameter for the isotopic exchange between the snow surface and the atmosphere. Using two independent laser spectrometers installed in parallel at Dome C, a well-established Picarro analyzer and a prototype of a new laser spectrometer developed for low-humidity environments, we document the atmospheric water vapor δ18O, δD, and d-excess over an entire 2.5-month summer season. The good agreement between the two instruments gives confidence in the accuracy and reliability of the measurements. These observations are valuable data to evaluate and improve isotope-enabled general circulation models, as demonstrated by our assessment of LMDZiso’s ability to capture the mean and diurnal cycle of the atmospheric water vapor isotopic composition.
Paper III integrates the knowledge and observational datasets from the two previous studies into a modeling approach to investigate the impact of surface processes on the isotopic signal across different time scales. Using an adapted version of the SNOWISO model for low-accumulation sites, we first identify that the seasonal isotopic signal observed in the snow surface can be explained by the combined effect of isotopic fractionation during vapor exchange and the continuous mixing of fresh precipitation with deposited snow. Including isotopic fractionation during vapor exchange also significantly improves the representation of the observed seasonal amplitude and monthly mean variability of the snow surface isotopic composition. We further show that vapor exchange affects the mean and variability of multi-decadal isotopic records. Specifically, isotopic fractionation during vapor exchange enriches the mean δ18O while reducing its inter-annual variability and decreases the mean d-excess while increasing its inter-annual variability. By testing different precipitation configurations, we show that precipitation intermittency influences the magnitude of the impact of isotopic vapor exchange on the isotopic records.
The three papers together offer a comprehensive and quantitative analysis of surface processes affecting the isotopic signals in the snow surface and deeper in the snowpack at Dome C. The findings of this thesis advance the understanding of isotopic signal formation at the ice sheet’s surface, which will contribute to refining the interpretation of ice core records.Doktorgradsavhandlin
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
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