1,720,979 research outputs found
Identification and Analysis of Collisional Breakup in Natural Rain
No full textNumerous laboratory and numerical studies have been dedicated to understanding collisional breakup as
one of the most important processes in rain formation. The present study aims to identify when, in natural
rain, collisional breakup is dominant and thus able to modify the shape of the raindrop size distribution
(DSD), up to the equilibrium DSD. To this end, an automated objective algorithm has been developed and
applied to a total of more than 6000 two-minute-averaged DSDs. Since breakup is mostly observed in heavy
precipitation, the method was applied to the DSDs where rain rate was above 5mm/h. The selected breakup
DSDs had good agreement with those predicted to be the equilibrium DSD by different theoretical models.
The equilibrium DSD was found in a variable fraction of the total samples (0%–7%), confirming that the
onset of equilibriumis a rare event in natural rain. The occurrence of aDSDin which breakup is dominant and
modifies the DSD but the equilibrium DSD is not reached is higher (15%–47%). The gamma distribution,
which has been widely used in the parameterization of observed size spectra, had a poor fitting in breakupinduced
DSD, especially in the 1.0–2.6-mm-diameter interval. This can impact applications for which the
parameterization of DSD is needed, such as in the retrieval of a DSD integral parameter (such as rain rate)
from active remote sensor data
Evaluation of Gamma Raindrop Size Distribution Assumption through Comparison of Rain Rates of Measured and Radar-Equivalent Gamma DSD
No full textTo date, one of the most widely used parametric forms for modeling raindrop size distribution (DSD) is the
three-parameter gamma. The aim of this paper is to analyze the error of assuming such parametric form to
model the natural DSDs. To achieve this goal, a methodology is set up to compare the rain rate obtained from
a disdrometer-measured drop size distribution with the rain rate of a gamma drop size distribution that
produces the same triplets of dual-polarization radar measurements, namely reflectivity factor, differential
reflectivity, and specific differential phase shift. In such a way, any differences between the values of the two
rain rates will provide information about how well the gamma distribution fits the measured precipitation. The
difference between rain rates is analyzed in terms of normalized standard error and normalized bias using
different radar frequencies, drop shape–size relations, and disdrometer integration time. The study is performed
using four datasets of DSDs collected by two-dimensional video disdrometers deployed in Huntsville (Alabama)
and in three different prelaunch campaigns of the NASA–Japan Aerospace Exploration Agency
(JAXA) Global Precipitation Measurement (GPM) ground validation program including the Hydrological
Cycle inMediterraneanExperiment (HyMeX) special observation period (SOP) 1 field campaign inRome. The
results show that differences in rain rates of the disdrometer DSD and the gamma DSD determining the same
dual-polarization radar measurements exist and exceed those related to the methodology itself and to the disdrometer
sampling error, supporting the finding that there is an error associatedwith the gammaDSDassumption
Comparison of GPM-CO and Ground-Based Radar Retrieval of Mass-Weighted Mean Rain Drop Diameter at Mid-Latitude
No full textOne of the main goals of the National Aeronautics and Space Administration (NASA) Global Precipitation Measurement (GPM) mission is to retrieve parameters of the raindrop size distribution (DSD) globally. As a standard product of the dual-frequency Precipitation Radar (DPR) on board GPM Core Satellite, the mass-weighted mean diameter, Dm, and the normalized intercept parameter, Nw, are estimated in three dimensions at the resolution of the radar. These are two parameters of the three-parameter gamma model DSD adopted by the GPM algorithms.
This study investigates the accuracy of the Dm retrieval through a comparative study of C-band ground radars (GR) and GPM products over Italy. The reliability of ground reference is tested by using two different approaches to estimate Dm. The results show good agreement between the ground based and space-borne derived Dm with an absolute bias being generally lower than 0.5 mm over land in stratiform precipitation for the DPR algorithm, and the combined DPR-GMI (GPM Microwave Imager) algorithm. For the DPR-GMI algorithm, the good agreement extends to convective precipitation as well. Estimates of Dm from the DPR High Sensitivity Ka-band (HS) data show slightly worse results.
A sensitivity study indicates that the accuracy of the Dm estimation is independent of the height above surface (not shown) and the distance from the ground radar. On the other hand, a non-uniform precipitation pattern (interpreted both as high variability and as a patchy spatial distribution) within the DPR footprint is usually associated with a significant error in the DPR-derived estimate of Dm
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
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