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Climate, clouds, and convection on Earth and Titan
Get PDFThe planets and moons in the solar system present a unique opportunity for enriching our understanding of Earth. The remarkable diversity of atmospheric compositions, dynamics, and weather patterns requires us to move beyond Earth-centric paradigms and search for more general theories that can explain the similarities and differences between them. In this work, Saturn's moon Titan is chosen as the point of comparison with Earth for its compositional similarity, active hydrological cycle, and distinct atmospheric dynamics. We investigate the governing physics of climate, clouds, and convection on both bodies with the goal of learning general truths that broadly apply to most, if not all, moist planetary atmospheres. We focus, in particular, on the effects of low to high moisture concentration in the atmosphere. First, it is found that Earth's climate is remarkably stable to significant changes in atmospheric moisture content. In Earth-like climate states, the vapor pressure path at the anvil cloud level is fixed due to spectroscopic properties of water vapor. The largest changes in Earth's climate occur at tipping points that involve transitions from multi-layered to single-layered convective clouds. Second, we demonstrate that the height of congestus cloud-top formation in the tropics is driven by a mid-tropospheric decline in the water vapor emissivity in clear-sky regions, which causes clouds to detrain preferentially between 5-6 km. This clear-sky theory of cloud formation is derived from basic assumptions of mass and energy balance and so should generalize well to other locations on Earth or to other planets and different atmospheric compositions. Third, we show that the transition from steady, quasi-equilibrium (QE) precipitation on Earth to non-steady, relaxed oscillator (RO) precipitation on Titan is predicted by the breakdown of a heat engine model of convection with increasing surface temperature and/or atmospheric moisture content. The breakdown of quasi-equilibrium dynamics occurs due to an imbalance between the work performed by the convective heat engine and the heat of condensation released by the convective motions themselves. The heat engine perspective offers a robust point of comparison between the atmospheres of Earth and Titan based on the first and second laws of thermodynamics, which are system invariant. The heat engine model is, in fact, agnostic of the working fluid and the condensing substance and, arguably, is the best framework to explain why dynamical similarities between present day Titan and a much warmer Earth exist
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
Data for Spaulding-Astudillo and Mitchell (2024a), "A simple model for the emergence of relaxation-oscillator convection"
No full text<p>Data for Spaulding-Astudillo and Mitchell (2024a), "A simple model for the emergence of relaxation-oscillator convection"</p>
<p>The main directories have a common nomenclature: e.g., minimal_1p1S_FSC_335K_N7200, where 1p1S indicates a solar constant 1.1 times the present day (1360), FSC indicates that it is a full-sky radiation run, 335 K is the surface temperature (fixed), and N7200 refers to the relaxation timescale of 7200 seconds for CAPE in the quasi-equilibrium closure to the convection scheme. </p>
<p>In every directory, each .nc file contains 5 years of model output. There are 5 types of .nc files, which correspond to different output streams of ECHAM6. The main output stream is ..._echam.nc, which has daily-averaged output.</p>
<p>The tendencies for gross deposition (gdep_ls) and gross condensation (gcnd_ls; both with units of kg/m2/s) from the large-scale scheme are in ..._g1am.nc. This is the mean-value stream, which records daily-averaged values. </p>
<p>The tendencies for gross condensation in convective updrafts are stored in the variable "ddf13" in ..._debugs.nc (units of kg/m2/s). This is another output stream, which records hourly values usually for debugging purposes. The total pressure as a function of height (units of Pa) is stored in the variable "ddf8". Also, the implied surface heat source/sink in the surface energy budget that keeps the surface temperature fixed in time is tracked in the variable "zdf8" (units of W/m2). </p>
<p>The experimental range of surface temperatures is 290-360 K, which remain fixed as a function of time in the simulations through the use of an artificial heat sink. The simulations are from the ECHAM6 climate model, which we ran in single-column mode. </p>
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
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