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Paul A. Hwang - One of the best experts on this subject based on the ideXlab platform.
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Surface wave Spectral properties of centimeter to decameter wavelengths: variable Spectral Slope and non-equilibrium spectrum
Ocean Dynamics, 2020Co-Authors: Paul A. HwangAbstract:Understanding the wave properties in centimeter to decameter (cmDm) wavelength range is of great interest to ocean remote sensing and air-sea interaction. For more than six decades, cmDm waves are generally considered to be in the equilibrium range, and its Spectral function has a constant Slope: − 5 or − 4 in the 1D frequency spectrum and − 3 or − 2.5 in the 1D wavenumber spectrum. Some variations of the equilibrium spectrum model include varying the frequency Spectral Slope from − 4 to − 5 at some multiple of the Spectral peak frequency, or incorporating a threshold velocity in the reference wind speed. Extensive efforts are then devoted to quantifying the Spectral coefficient of the equilibrium spectrum function. This paper emphasizes that the observed wave Spectral Slope in the ocean is mostly non-constant. Therefore, the wave properties in field observations are significantly different from those inferred from assuming a constant Spectral Slope. The variable Spectral Slope is indicative of a non-equilibrium nature of ocean surface waves. Furthermore, from signal-to-noise consideration, surface Slope is much more suited than elevation for evaluating the Spectral Slope and for quantifying the cmDm wave properties. Microwave sensors are excellent instruments for providing the ocean surface Slope measurements. Several large datasets of lowpass-filtered mean square Slope (LPMSS) have been reported recently. Combining the LPMSS observations with a spectrum function that accommodates a variable Spectral Slope, several quantitative results on the variable Spectral Slope and cmDm wave properties are presented.
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Variable Spectral Slope and Nonequilibrium Surface Wave Spectrum
arXiv: Atmospheric and Oceanic Physics, 2019Co-Authors: Paul A. HwangAbstract:The wave Spectral properties in the centimeter to decameter (cmDm) wavelength range is of great interest to ocean remote sensing and studies of ocean surface processes including the surface roughness, air-sea energy and momentum exchanges, wave breaking, and whitecap coverage. For more than six decades, the cmDm wave components are generally considered to be in the equilibrium range, and its Spectral function has a constant Slope: -5 or -4 in the 1D frequency spectrum, and -3 or -2.5 in the 1D wavenumber spectrum. Some variations of the equilibrium spectrum models include varying the frequency Spectral Slope from 4 to 5 at some multiple of the Spectral peak frequency, or incorporating a threshold velocity in the reference wind speed. Extensive efforts are then devoted to quantifying the Spectral coefficient of the equilibrium spectrum function. The observed wind wave Spectral Slopes in the ocean environment, however, are rarely constant. The variable Spectral Slope is indicative of the nonequilibrium nature of surface wind waves in the field. As a result the wave properties in field observations are significantly different from those inferred from assuming a constant Spectral Slope. From signal-to-noise consideration the surface Slope measurements are much more sensitive than the elevation data for the study of cmDm waves. Recently, several large datasets of low-pass-filtered mean square Slope (LPMSS) have been reported in support of the Global Navigation Satellite System Reflectometry (GNSSR) tropical cyclone wind sensing effort. Combining the LPMSS observations with a spectrum model that accommodates a variable Spectral Slope, this paper seeks to quantify the connection between the variable Spectral Slope and the Spectral properties of cmDm waves.
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Airborne Measurements of the Wavenumber Spectra of Ocean Surface Waves. Part I: Spectral Slope and Dimensionless Spectral Coefficient*
Journal of Physical Oceanography, 2000Co-Authors: Paul A. Hwang, David W. Wang, Edward J. Walsh, William B. Krabill, Robert N. SwiftAbstract:An airborne scanning lidar system acquires 3D spatial topography of ocean surface waves. From the spatial data, wavenumber spectra are computed directly. The Spectral analyses of two distinctively different wave fields are presented. The first one is a quasi-steady wave field under active wind generation, and the second one is a decaying wave field following a slackening of the wind field. Subtle differences in different representations of the one-dimensional spectrum (omnidirectional, marginal, and traverse) are illustrated. The Spectral properties in terms of the dimensionless Spectral coefficient and Spectral Slope in the equilibrium range are investigated using the wavenumber spectra directly computed from the 3D topography of the ocean surface. The results are in excellent agreement with existing data. The rapid data acquisition afforded by an airborne system provides an enhanced capability for studying the spatial variation of a wave field with minimal temporal changes in the environmental forcing conditions. The data of the 3D surface topography are also ideal for the quantitative investigation of the directional properties of a random wave field.
M Elvis - One of the best experts on this subject based on the ideXlab platform.
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the sloan digital sky survey xmm newton quasar survey correlation between x ray Spectral Slope and eddington ratio
The Astrophysical Journal, 2009Co-Authors: G Risaliti, M Young, M ElvisAbstract:We present a correlation between the 2-10 keV Spectral Slope {gamma} {sub X} and the Eddington ratio L/L{sub EDD} in a sample of {approx}400 Sloan Digital Sky Survey (SDSS) quasars with available hard X-ray spectra from XMM-Newton serendipitous observations. We find that the {gamma} {sub X}-L/L {sub EDD} correlation is strongest in objects with black hole (BH) masses determined from the H{beta} line, and weaker (but still present) for those based on Mg II. An empirical nonlinear correction of the Mg II-based masses, obtained by comparing the mass estimates in SDSS quasars having both H{beta} and Mg II measurements, significantly increases the strength of the correlation. No correlation is found among objects with BH masses derived from C IV, confirming that this line is not a reliable indicator of the BH mass. No significant correlation is found with the bolometric luminosity, while a {gamma} {sub X}-M {sub BH} relation is present, though with a lower statistical significance than between {gamma} {sub X} and L/L {sub EDD}. Our results imply a physical link between the accretion efficiency in the (cold) accretion disk of active galactic nuclei and the physical status of the (hot) corona responsible for the X-ray emission.
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THE SLOAN DIGITAL SKY SURVEY/XMM-NEWTON QUASAR SURVEY: CORRELATION BETWEEN X-RAY Spectral Slope AND EDDINGTON RATIO
The Astrophysical Journal, 2009Co-Authors: G Risaliti, M Young, M ElvisAbstract:We present a correlation between the 2-10 keV Spectral Slope {gamma} {sub X} and the Eddington ratio L/L{sub EDD} in a sample of {approx}400 Sloan Digital Sky Survey (SDSS) quasars with available hard X-ray spectra from XMM-Newton serendipitous observations. We find that the {gamma} {sub X}-L/L {sub EDD} correlation is strongest in objects with black hole (BH) masses determined from the H{beta} line, and weaker (but still present) for those based on Mg II. An empirical nonlinear correction of the Mg II-based masses, obtained by comparing the mass estimates in SDSS quasars having both H{beta} and Mg II measurements, significantly increases the strength of the correlation. No correlation is found among objects with BH masses derived from C IV, confirming that this line is not a reliable indicator of the BH mass. No significant correlation is found with the bolometric luminosity, while a {gamma} {sub X}-M {sub BH} relation is present, though with a lower statistical significance than between {gamma} {sub X} and L/L {sub EDD}. Our results imply a physical link between the accretion efficiency in the (cold) accretion disk of active galactic nuclei and the physical status of the (hot) corona responsible for the X-ray emission.
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the sdss xmm newton quasar survey correlation between x ray Spectral Slope and eddington ratio
arXiv: Cosmology and Nongalactic Astrophysics, 2009Co-Authors: G Risaliti, M Young, M ElvisAbstract:We present a correlation between the 2-10 keV Spectral Slope Gamma and the Eddington ratio L/L_{EDD} in a sample of ~400 Sloan Digital Sky Survey quasars with available hard X-ray spectra from XMM-Newton serendipitous observations. We find that the Gamma-L/L_{EDD} correlation is strongest in objects with black hole (BH) masses determined from the Hbeta line, and weaker (but still present) for those based on Mg II. An empirical non-linear correction of the Mg II-based masses, obtained by comparing the mass estimates in SDSS quasars having both Hbeta and Mg II measurements, significantly increases the strength of the correlation. No correlation is found among objects with BH masses derived from C IV, confirming that this line is not a reliable indicator of the BH mass. No significant correlation is found with the bolometric luminosity, while a Gamma-M_BH relation is present, though with a lower statistical significance than between Gamma and L/L_{EDD}. Our results imply a physical link between the accretion efficiency in the (cold) accretion disc of AGNs and the physical status of the (hot) corona responsible for the X-ray emission.
G Risaliti - One of the best experts on this subject based on the ideXlab platform.
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the sloan digital sky survey xmm newton quasar survey correlation between x ray Spectral Slope and eddington ratio
The Astrophysical Journal, 2009Co-Authors: G Risaliti, M Young, M ElvisAbstract:We present a correlation between the 2-10 keV Spectral Slope {gamma} {sub X} and the Eddington ratio L/L{sub EDD} in a sample of {approx}400 Sloan Digital Sky Survey (SDSS) quasars with available hard X-ray spectra from XMM-Newton serendipitous observations. We find that the {gamma} {sub X}-L/L {sub EDD} correlation is strongest in objects with black hole (BH) masses determined from the H{beta} line, and weaker (but still present) for those based on Mg II. An empirical nonlinear correction of the Mg II-based masses, obtained by comparing the mass estimates in SDSS quasars having both H{beta} and Mg II measurements, significantly increases the strength of the correlation. No correlation is found among objects with BH masses derived from C IV, confirming that this line is not a reliable indicator of the BH mass. No significant correlation is found with the bolometric luminosity, while a {gamma} {sub X}-M {sub BH} relation is present, though with a lower statistical significance than between {gamma} {sub X} and L/L {sub EDD}. Our results imply a physical link between the accretion efficiency in the (cold) accretion disk of active galactic nuclei and the physical status of the (hot) corona responsible for the X-ray emission.
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THE SLOAN DIGITAL SKY SURVEY/XMM-NEWTON QUASAR SURVEY: CORRELATION BETWEEN X-RAY Spectral Slope AND EDDINGTON RATIO
The Astrophysical Journal, 2009Co-Authors: G Risaliti, M Young, M ElvisAbstract:We present a correlation between the 2-10 keV Spectral Slope {gamma} {sub X} and the Eddington ratio L/L{sub EDD} in a sample of {approx}400 Sloan Digital Sky Survey (SDSS) quasars with available hard X-ray spectra from XMM-Newton serendipitous observations. We find that the {gamma} {sub X}-L/L {sub EDD} correlation is strongest in objects with black hole (BH) masses determined from the H{beta} line, and weaker (but still present) for those based on Mg II. An empirical nonlinear correction of the Mg II-based masses, obtained by comparing the mass estimates in SDSS quasars having both H{beta} and Mg II measurements, significantly increases the strength of the correlation. No correlation is found among objects with BH masses derived from C IV, confirming that this line is not a reliable indicator of the BH mass. No significant correlation is found with the bolometric luminosity, while a {gamma} {sub X}-M {sub BH} relation is present, though with a lower statistical significance than between {gamma} {sub X} and L/L {sub EDD}. Our results imply a physical link between the accretion efficiency in the (cold) accretion disk of active galactic nuclei and the physical status of the (hot) corona responsible for the X-ray emission.
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the sdss xmm newton quasar survey correlation between x ray Spectral Slope and eddington ratio
arXiv: Cosmology and Nongalactic Astrophysics, 2009Co-Authors: G Risaliti, M Young, M ElvisAbstract:We present a correlation between the 2-10 keV Spectral Slope Gamma and the Eddington ratio L/L_{EDD} in a sample of ~400 Sloan Digital Sky Survey quasars with available hard X-ray spectra from XMM-Newton serendipitous observations. We find that the Gamma-L/L_{EDD} correlation is strongest in objects with black hole (BH) masses determined from the Hbeta line, and weaker (but still present) for those based on Mg II. An empirical non-linear correction of the Mg II-based masses, obtained by comparing the mass estimates in SDSS quasars having both Hbeta and Mg II measurements, significantly increases the strength of the correlation. No correlation is found among objects with BH masses derived from C IV, confirming that this line is not a reliable indicator of the BH mass. No significant correlation is found with the bolometric luminosity, while a Gamma-M_BH relation is present, though with a lower statistical significance than between Gamma and L/L_{EDD}. Our results imply a physical link between the accretion efficiency in the (cold) accretion disc of AGNs and the physical status of the (hot) corona responsible for the X-ray emission.
Ronald Benner - One of the best experts on this subject based on the ideXlab platform.
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the Spectral Slope coefficient of chromophoric dissolved organic matter s275 295 as a tracer of terrigenous dissolved organic carbon in river influenced ocean margins
Limnology and Oceanography, 2012Co-Authors: Cédric G. Fichot, Ronald BennerAbstract:The present study demonstrates that the Spectral Slope coefficient of chromophoric dissolved organic matter (CDOM) between 275 nm and 295 nm (S275–295) can be used as a tracer of the percent terrigenous dissolved organic carbon (%tDOC) in river-influenced ocean margins, where rivers exert an important control on carbon dynamics and CO2 fluxes. Absorption coefficients of CDOM and concentrations of dissolved organic carbon (DOC) and dissolved lignin were measured on a seasonal basis in the Mississippi and Atchafalaya rivers and in surface waters of the northern Gulf of Mexico (NGoM). A strong, linear relationship between lignin concentrations and CDOM absorption coefficients indicated lignin is an important chromophore in this environment. The dual nature of lignin as an important chromophore in CDOM and as a terrigenous component of DOC facilitated development of the tracer. The applicability of the tracer relies on the existence of a strong, nonlinear relationship between S275–295 and the DOC-normalized lignin yield in rivers and along the freshwater– marine continuum in the NGoM. Physical mixing and the effects of photodegradation on S275–295 and dissolved lignin were largely responsible for maintaining this relationship, suggesting the tracer is applicable to surface waters of most river-influenced ocean margins. The Spectral Slope coefficient (S275–295) provides new capabilities to trace tDOC on synoptic scales of relevance to ocean margins and represents an important tool for improving ocean carbon budgets. The key processes controlling carbon transformations in ocean margins remain poorly quantified, thereby limiting our understanding of how the coastal ocean affects the ocean carbon cycle and atmospheric CO2. Ocean margins account for , 10% of the global ocean surface area but
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The Spectral Slope coefficient of chromophoric dissolved organic matter (S275–295) as a tracer of terrigenous dissolved organic carbon in river‐influenced ocean margins
Limnology and Oceanography, 2012Co-Authors: Cédric G. Fichot, Ronald BennerAbstract:The present study demonstrates that the Spectral Slope coefficient of chromophoric dissolved organic matter (CDOM) between 275 nm and 295 nm (S275–295) can be used as a tracer of the percent terrigenous dissolved organic carbon (%tDOC) in river-influenced ocean margins, where rivers exert an important control on carbon dynamics and CO2 fluxes. Absorption coefficients of CDOM and concentrations of dissolved organic carbon (DOC) and dissolved lignin were measured on a seasonal basis in the Mississippi and Atchafalaya rivers and in surface waters of the northern Gulf of Mexico (NGoM). A strong, linear relationship between lignin concentrations and CDOM absorption coefficients indicated lignin is an important chromophore in this environment. The dual nature of lignin as an important chromophore in CDOM and as a terrigenous component of DOC facilitated development of the tracer. The applicability of the tracer relies on the existence of a strong, nonlinear relationship between S275–295 and the DOC-normalized lignin yield in rivers and along the freshwater– marine continuum in the NGoM. Physical mixing and the effects of photodegradation on S275–295 and dissolved lignin were largely responsible for maintaining this relationship, suggesting the tracer is applicable to surface waters of most river-influenced ocean margins. The Spectral Slope coefficient (S275–295) provides new capabilities to trace tDOC on synoptic scales of relevance to ocean margins and represents an important tool for improving ocean carbon budgets. The key processes controlling carbon transformations in ocean margins remain poorly quantified, thereby limiting our understanding of how the coastal ocean affects the ocean carbon cycle and atmospheric CO2. Ocean margins account for , 10% of the global ocean surface area but
M Young - One of the best experts on this subject based on the ideXlab platform.
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the sloan digital sky survey xmm newton quasar survey correlation between x ray Spectral Slope and eddington ratio
The Astrophysical Journal, 2009Co-Authors: G Risaliti, M Young, M ElvisAbstract:We present a correlation between the 2-10 keV Spectral Slope {gamma} {sub X} and the Eddington ratio L/L{sub EDD} in a sample of {approx}400 Sloan Digital Sky Survey (SDSS) quasars with available hard X-ray spectra from XMM-Newton serendipitous observations. We find that the {gamma} {sub X}-L/L {sub EDD} correlation is strongest in objects with black hole (BH) masses determined from the H{beta} line, and weaker (but still present) for those based on Mg II. An empirical nonlinear correction of the Mg II-based masses, obtained by comparing the mass estimates in SDSS quasars having both H{beta} and Mg II measurements, significantly increases the strength of the correlation. No correlation is found among objects with BH masses derived from C IV, confirming that this line is not a reliable indicator of the BH mass. No significant correlation is found with the bolometric luminosity, while a {gamma} {sub X}-M {sub BH} relation is present, though with a lower statistical significance than between {gamma} {sub X} and L/L {sub EDD}. Our results imply a physical link between the accretion efficiency in the (cold) accretion disk of active galactic nuclei and the physical status of the (hot) corona responsible for the X-ray emission.
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THE SLOAN DIGITAL SKY SURVEY/XMM-NEWTON QUASAR SURVEY: CORRELATION BETWEEN X-RAY Spectral Slope AND EDDINGTON RATIO
The Astrophysical Journal, 2009Co-Authors: G Risaliti, M Young, M ElvisAbstract:We present a correlation between the 2-10 keV Spectral Slope {gamma} {sub X} and the Eddington ratio L/L{sub EDD} in a sample of {approx}400 Sloan Digital Sky Survey (SDSS) quasars with available hard X-ray spectra from XMM-Newton serendipitous observations. We find that the {gamma} {sub X}-L/L {sub EDD} correlation is strongest in objects with black hole (BH) masses determined from the H{beta} line, and weaker (but still present) for those based on Mg II. An empirical nonlinear correction of the Mg II-based masses, obtained by comparing the mass estimates in SDSS quasars having both H{beta} and Mg II measurements, significantly increases the strength of the correlation. No correlation is found among objects with BH masses derived from C IV, confirming that this line is not a reliable indicator of the BH mass. No significant correlation is found with the bolometric luminosity, while a {gamma} {sub X}-M {sub BH} relation is present, though with a lower statistical significance than between {gamma} {sub X} and L/L {sub EDD}. Our results imply a physical link between the accretion efficiency in the (cold) accretion disk of active galactic nuclei and the physical status of the (hot) corona responsible for the X-ray emission.
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the sdss xmm newton quasar survey correlation between x ray Spectral Slope and eddington ratio
arXiv: Cosmology and Nongalactic Astrophysics, 2009Co-Authors: G Risaliti, M Young, M ElvisAbstract:We present a correlation between the 2-10 keV Spectral Slope Gamma and the Eddington ratio L/L_{EDD} in a sample of ~400 Sloan Digital Sky Survey quasars with available hard X-ray spectra from XMM-Newton serendipitous observations. We find that the Gamma-L/L_{EDD} correlation is strongest in objects with black hole (BH) masses determined from the Hbeta line, and weaker (but still present) for those based on Mg II. An empirical non-linear correction of the Mg II-based masses, obtained by comparing the mass estimates in SDSS quasars having both Hbeta and Mg II measurements, significantly increases the strength of the correlation. No correlation is found among objects with BH masses derived from C IV, confirming that this line is not a reliable indicator of the BH mass. No significant correlation is found with the bolometric luminosity, while a Gamma-M_BH relation is present, though with a lower statistical significance than between Gamma and L/L_{EDD}. Our results imply a physical link between the accretion efficiency in the (cold) accretion disc of AGNs and the physical status of the (hot) corona responsible for the X-ray emission.
