1,720,980 research outputs found
Diagnosing the Beating Heart of Our Atmosphere: A Puzzle for Future Generations
Get PDFAs concerns and debates grow over global climate change, scientists forge ahead toward grasping a better understanding of climate variability. In the atmosphere (an integral component of our climate system), research efforts are unraveling its fundamental global pattern that accounts for much of the changing wintertime meteorological conditions. As the heart of our atmosphere, this pattern beats in time but becomes arrhythmic in association with unusual atmospheric occurrences 30,000 feet above ground. To date, our limited knowledge of the atmosphere at these lofty heights and computational constraints make the diagnosis of this heart condition difficult and uncertain. With rapid development in technology that will allow us to better observe and simulate the atmosphere, this difficulty, which clouds our ability to assess future climate change, may be overcome by future generations.https://digitalcommons.coastal.edu/dtsls/1004/thumbnail.jp
Tropical dynamics near the stratospause: the two-day wave and its relatives
No full textThesis (Ph.D.) University of Washington, 1998The two-day wave is observed in the Upper Atmosphere Research Satellite (UARS) Microwave Limb Sounder (MLS) temperature and water vapor data. During a 3-year period (Dec. 1991-Sep. 1994), the wave signature is prominent semiannually after each solstice and is comprised of a zonal wavenumber 3 component with -day period and a wavenumber 4 component with -day period. Intra-annually, the wavenumber 3 amplitude during the austral summer is nearly twice as strong as during the boreal summer. The wavenumber 4 component however can be equally strong in both summers. The wave-number 3 signal tends to be dominant during the austral summer while the wave 4 component is dominant during the boreal summer. The derived zonal wind structure suggests that the Charney-Stern inflection instability mechanism is responsible for generating the two-day wave whose amplitude resides mainly on the equatorward flank of the summer easterly jet.In some seasons, momentum redistribution by inertial instability appears to destabilize the easterly jet from which the barotropically unstable two-day wave grows. In these instances, an independent study using the UARS Cryogenic Limb Array Etalon Spectrometer (CLAES) temperature (Hayashi et al., 1998) coincidently identifies "pancake" structures associated with inertial instability. A possible connection between inertial instability and the two-day wave has been discussed by Hitchman (1985) and Orsolini et al. (1997).The National Center for Atmospheric Research (NCAR) Community Climate Model version 2 (CCM2) mechanistic model is used to simulate this connection. Model experiments show that, for a prescribed initial wind condition with strong horizontal wind shear in the tropics, inertial instability can trigger the two-day wave. An increase in easterly wind curvature fostered by inertial instability circulation destabilizes the jet in low summer latitudes and allows first the growth of the wavenumber 4 then the wavenumber 3 component of the two-day wave. Near the stratopause, the two-day wave energy propagation is directed equatorward away from the wave's critical line source and westerly momentum is fluxed into the easterly jet core by the wave. While much of the wavenumber 4 activity is confined near the stratopause, the wavenumber 3 energy can propagate upward well into the mesosphere where strong Rayleigh damping is imposed. The simulated waves' spatial and spectral characteristics are fairly realistic
Dynamics of Annular Variability (Extended Abstract)
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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
Eastward-Propagating Planetary Waves Prior to the January 2009 Sudden Stratospheric Warming
No full textEastward-propagating planetary waves (EPWs) were investigated prior to the boreal January 2009 major sudden stratospheric warming (SSW) event simulated by the National Center for Atmospheric Research's Whole Atmosphere Community Climate Model with specified dynamics. About 22 days before SSW onset, a background flow with jet maxima around the upper polar stratosphere and subtropical mesosphere developed due to the net forcing by gravity and planetary waves. The mesospheric wind structure was largely unstable and supported a wave geometry conducive to overreflection. With a zonal phase speed of ∼10 m s−1, EPWs appeared near their turning and critical layers as wavenumber-2 perturbations in the stratosphere and mesosphere. Accompanied by upward EPW activity from the lower stratosphere, EPW growth exhibited characteristics of wave instability and overreflection
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
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