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Hund-der Yeh - One of the best experts on this subject based on the ideXlab platform.

  • stochastic modeling of variations in stream flow discharge induced by random spatiotemporal fluctuations in lateral Inflow Rate
    Stochastic Environmental Research and Risk Assessment, 2016
    Co-Authors: Ching Min Chang, Hund-der Yeh
    Abstract:

    Due to natural heterogeneity in runoff processes, the analysis of response of stream channels to the variation of lateral Inflow is therefore viewed in terms of stochastic spatiotemporal processes. Based on the representation theorem, a closed-form expression is derived to describe the spectral response characteristic of stream subject to spatiotemporal fluctuations in lateral Inflow. It provides a basis for evaluating the induced discharge variability in stream channels. It is found that the evolutionary power spectrum of the stream flow discharge process and therefore the variance is increased with the distance from the upstream boundary and the characteristic length scale of the lateral Inflow process. Flow discharge prediction in the downstream region has a high degree of uncertainty by solving the deterministic partial differential equation.

  • Variability of flow discharge in lateral Inflow-dominated stream channels
    Hydrology and Earth System Sciences, 2015
    Co-Authors: Ching Min Chang, Hund-der Yeh
    Abstract:

    The influence of the temporal changes in lateral Inflow Rate on the discharge variability in stream channels is explored through the analysis of the diffusion wave equation (i.e. the linearized Saint-Venant equation). To account for variability and uncertainty, the lateral Inflow Rate is regarded as a temporal random function. On the basis of the spectral representation theory, analytical expressions for the covariance function and evolutionary power spectral density of the random discharge perturbation process are derived to quantify variability in stream flow discharge induced by the temporal changes in lateral Inflow Rate. The treatment of the discharge variance (square root of the variance) gives us a quantitative estimate of uncertainty in predictions from the deterministic model. It is found that the discharge variability of stream flow is very large in the downstream reach, indicating large uncertainty anticipated from the use of the deterministic model. A larger temporal correlation scale of Inflow Rate fluctuations, representing more temporal consistency of fluctuations in Inflow Rate around the mean, introduces a higher variability in stream flow discharge.

  • Technical Note: Variability of flow discharge in lateral Inflow-dominated stream channels
    Hydrology and Earth System Sciences Discussions, 2015
    Co-Authors: Ching Min Chang, Hund-der Yeh
    Abstract:

    Abstract. The influence of the temporal changes in lateral Inflow Rate on the discharge variability in stream channels is explored through the analysis of diffusion wave equation (the linearized St. Venant equations). To account for variability and uncertainty, the lateral Inflow Rate is regarded as a temporal random function. Based on the spectral representation theory, analytical expressions for the covariance function and evolutionary power spectral density of the random discharge perturbation process are derived to quantify variability in stream flow discharge induced by the temporal changes in lateral Inflow Rate. Upon evaluating the closed-form expressions, it is found that the variability in stream flow discharge increases with distance from the upstream boundary of the channel and time as well. The temporal correlation scale of Inflow Rate fluctuations plays a positive role in enhancing the variability of the flow discharge in channels. The treatment of the discharge variance gives us a quantitative estimate of uncertainty from the use of the deterministic model.

  • Variability of stream flow discharge in response to self-similar random fields of temporal fluctuations in lateral Inflow Rate
    Journal of Hydrology, 2014
    Co-Authors: Ching Min Chang, Hund-der Yeh
    Abstract:

    Summary This article presents the use of stochastic methodology for quantitative analysis of variability in stream flow discharge in response to fluctuations in lateral Inflow Rate, where the lateral Inflow Rate is considered to be the difference between rainfall and infiltration Rates. In this work, we focus on the case where the temporal correlation structure of the fluctuations in the lateral Inflow Rate can be characterized by the statistics of random fractals. A closed-form expression quantifying the stream flow variability is therefore developed to investigate the influence of the fractal dimension of lateral Inflow process and the size of time domain. It is found that the stream flow discharge variability increases with the time domain size, while the fractal dimension of lateral Inflow process plays a role in the smoothness of fluctuations in stream flow discharge around the mean.

Ching Min Chang - One of the best experts on this subject based on the ideXlab platform.

  • stochastic modeling of variations in stream flow discharge induced by random spatiotemporal fluctuations in lateral Inflow Rate
    Stochastic Environmental Research and Risk Assessment, 2016
    Co-Authors: Ching Min Chang, Hund-der Yeh
    Abstract:

    Due to natural heterogeneity in runoff processes, the analysis of response of stream channels to the variation of lateral Inflow is therefore viewed in terms of stochastic spatiotemporal processes. Based on the representation theorem, a closed-form expression is derived to describe the spectral response characteristic of stream subject to spatiotemporal fluctuations in lateral Inflow. It provides a basis for evaluating the induced discharge variability in stream channels. It is found that the evolutionary power spectrum of the stream flow discharge process and therefore the variance is increased with the distance from the upstream boundary and the characteristic length scale of the lateral Inflow process. Flow discharge prediction in the downstream region has a high degree of uncertainty by solving the deterministic partial differential equation.

  • Variability of flow discharge in lateral Inflow-dominated stream channels
    Hydrology and Earth System Sciences, 2015
    Co-Authors: Ching Min Chang, Hund-der Yeh
    Abstract:

    The influence of the temporal changes in lateral Inflow Rate on the discharge variability in stream channels is explored through the analysis of the diffusion wave equation (i.e. the linearized Saint-Venant equation). To account for variability and uncertainty, the lateral Inflow Rate is regarded as a temporal random function. On the basis of the spectral representation theory, analytical expressions for the covariance function and evolutionary power spectral density of the random discharge perturbation process are derived to quantify variability in stream flow discharge induced by the temporal changes in lateral Inflow Rate. The treatment of the discharge variance (square root of the variance) gives us a quantitative estimate of uncertainty in predictions from the deterministic model. It is found that the discharge variability of stream flow is very large in the downstream reach, indicating large uncertainty anticipated from the use of the deterministic model. A larger temporal correlation scale of Inflow Rate fluctuations, representing more temporal consistency of fluctuations in Inflow Rate around the mean, introduces a higher variability in stream flow discharge.

  • Technical Note: Variability of flow discharge in lateral Inflow-dominated stream channels
    Hydrology and Earth System Sciences Discussions, 2015
    Co-Authors: Ching Min Chang, Hund-der Yeh
    Abstract:

    Abstract. The influence of the temporal changes in lateral Inflow Rate on the discharge variability in stream channels is explored through the analysis of diffusion wave equation (the linearized St. Venant equations). To account for variability and uncertainty, the lateral Inflow Rate is regarded as a temporal random function. Based on the spectral representation theory, analytical expressions for the covariance function and evolutionary power spectral density of the random discharge perturbation process are derived to quantify variability in stream flow discharge induced by the temporal changes in lateral Inflow Rate. Upon evaluating the closed-form expressions, it is found that the variability in stream flow discharge increases with distance from the upstream boundary of the channel and time as well. The temporal correlation scale of Inflow Rate fluctuations plays a positive role in enhancing the variability of the flow discharge in channels. The treatment of the discharge variance gives us a quantitative estimate of uncertainty from the use of the deterministic model.

  • Variability of stream flow discharge in response to self-similar random fields of temporal fluctuations in lateral Inflow Rate
    Journal of Hydrology, 2014
    Co-Authors: Ching Min Chang, Hund-der Yeh
    Abstract:

    Summary This article presents the use of stochastic methodology for quantitative analysis of variability in stream flow discharge in response to fluctuations in lateral Inflow Rate, where the lateral Inflow Rate is considered to be the difference between rainfall and infiltration Rates. In this work, we focus on the case where the temporal correlation structure of the fluctuations in the lateral Inflow Rate can be characterized by the statistics of random fractals. A closed-form expression quantifying the stream flow variability is therefore developed to investigate the influence of the fractal dimension of lateral Inflow process and the size of time domain. It is found that the stream flow discharge variability increases with the time domain size, while the fractal dimension of lateral Inflow process plays a role in the smoothness of fluctuations in stream flow discharge around the mean.

Tobias Westmeier - One of the best experts on this subject based on the ideXlab platform.

  • The COS/UVES absorption survey of the Magellanic stream. III. ionization, total mass, and Inflow Rate onto the Milky Way
    The Astrophysical Journal, 2014
    Co-Authors: Andrew J. Fox, Bart P. Wakker, Kathleen A. Barger, Audra K. Hernandez, Philipp Richter, Nicolas Lehner, Joss Bland-hawthorn, Jane C. Charlton, Tobias Westmeier, Christopher Thom
    Abstract:

    Dynamic interactions between the two Magellanic Clouds have flung large quantities of gas into the halo of the Milky Way. The result is a spectacular arrangement of gaseous structures, including the Magellanic Stream, the Magellanic Bridge, and the Leading Arm (collectively referred to as the Magellanic System). In this third paper of a series studying the Magellanic gas in absorption, we analyze the gas ionization level using a sample of 69 Hubble Space Telescope/Cosmic Origins Spectrograph sightlines that pass through or within 30° of the 21 cm emitting regions. We find that 81% (56/69) of the sightlines show UV absorption at Magellanic velocities, indicating that the total cross-section of the Magellanic System is ≈11,000 deg{sup 2}, or around one-quarter of the entire sky. Using observations of the Si III/Si II ratio together with Cloudy photoionization modeling, we calculate the total gas mass (atomic plus ionized) of the Magellanic System to be ≈2.0 × 10{sup 9} M {sub ☉} (d/55 kpc){sup 2}, with the ionized gas contributing around three times as much mass as the atomic gas. This is larger than the current-day interstellar H I mass of both Magellanic Clouds combined, indicating that they have lost most of their initialmore » gas mass. If the gas in the Magellanic System survives to reach the Galactic disk over its Inflow time of ∼0.5-1.0 Gyr, it will represent an average Inflow Rate of ∼3.7-6.7 M {sub ☉} yr{sup –1}, potentially raising the Galactic star formation Rate. However, multiple signs of an evaporative interaction with the hot Galactic corona indicate that the Magellanic gas may not survive its journey to the disk fully intact and will instead add material to (and cool) the corona.« less

  • the cos uves absorption survey of the magellanic stream iii ionization total mass and Inflow Rate onto the milky way
    The Astrophysical Journal, 2014
    Co-Authors: Andrew J. Fox, Bart P. Wakker, Kathleen A. Barger, Audra K. Hernandez, Philipp Richter, Nicolas Lehner, Jane C. Charlton, Joss Blandhawthorn, Tobias Westmeier
    Abstract:

    Dynamic interactions between the two Magellanic Clouds have flung large quantities of gas into the halo of the Milky Way. The result is a spectacular arrangement of gaseous structures, including the Magellanic Stream, the Magellanic Bridge, and the Leading Arm (collectively referred to as the Magellanic System). In this third paper of a series studying the Magellanic gas in absorption, we analyze the gas ionization level using a sample of 69 Hubble Space Telescope/Cosmic Origins Spectrograph sightlines that pass through or within 30° of the 21 cm emitting regions. We find that 81% (56/69) of the sightlines show UV absorption at Magellanic velocities, indicating that the total cross-section of the Magellanic System is ≈11,000 deg{sup 2}, or around one-quarter of the entire sky. Using observations of the Si III/Si II ratio together with Cloudy photoionization modeling, we calculate the total gas mass (atomic plus ionized) of the Magellanic System to be ≈2.0 × 10{sup 9} M {sub ☉} (d/55 kpc){sup 2}, with the ionized gas contributing around three times as much mass as the atomic gas. This is larger than the current-day interstellar H I mass of both Magellanic Clouds combined, indicating that they have lost most of their initialmore » gas mass. If the gas in the Magellanic System survives to reach the Galactic disk over its Inflow time of ∼0.5-1.0 Gyr, it will represent an average Inflow Rate of ∼3.7-6.7 M {sub ☉} yr{sup –1}, potentially raising the Galactic star formation Rate. However, multiple signs of an evaporative interaction with the hot Galactic corona indicate that the Magellanic gas may not survive its journey to the disk fully intact and will instead add material to (and cool) the corona.« less

Kathleen A. Barger - One of the best experts on this subject based on the ideXlab platform.

  • The COS/UVES absorption survey of the Magellanic stream. III. ionization, total mass, and Inflow Rate onto the Milky Way
    The Astrophysical Journal, 2014
    Co-Authors: Andrew J. Fox, Bart P. Wakker, Kathleen A. Barger, Audra K. Hernandez, Philipp Richter, Nicolas Lehner, Joss Bland-hawthorn, Jane C. Charlton, Tobias Westmeier, Christopher Thom
    Abstract:

    Dynamic interactions between the two Magellanic Clouds have flung large quantities of gas into the halo of the Milky Way. The result is a spectacular arrangement of gaseous structures, including the Magellanic Stream, the Magellanic Bridge, and the Leading Arm (collectively referred to as the Magellanic System). In this third paper of a series studying the Magellanic gas in absorption, we analyze the gas ionization level using a sample of 69 Hubble Space Telescope/Cosmic Origins Spectrograph sightlines that pass through or within 30° of the 21 cm emitting regions. We find that 81% (56/69) of the sightlines show UV absorption at Magellanic velocities, indicating that the total cross-section of the Magellanic System is ≈11,000 deg{sup 2}, or around one-quarter of the entire sky. Using observations of the Si III/Si II ratio together with Cloudy photoionization modeling, we calculate the total gas mass (atomic plus ionized) of the Magellanic System to be ≈2.0 × 10{sup 9} M {sub ☉} (d/55 kpc){sup 2}, with the ionized gas contributing around three times as much mass as the atomic gas. This is larger than the current-day interstellar H I mass of both Magellanic Clouds combined, indicating that they have lost most of their initialmore » gas mass. If the gas in the Magellanic System survives to reach the Galactic disk over its Inflow time of ∼0.5-1.0 Gyr, it will represent an average Inflow Rate of ∼3.7-6.7 M {sub ☉} yr{sup –1}, potentially raising the Galactic star formation Rate. However, multiple signs of an evaporative interaction with the hot Galactic corona indicate that the Magellanic gas may not survive its journey to the disk fully intact and will instead add material to (and cool) the corona.« less

  • the cos uves absorption survey of the magellanic stream iii ionization total mass and Inflow Rate onto the milky way
    The Astrophysical Journal, 2014
    Co-Authors: Andrew J. Fox, Bart P. Wakker, Kathleen A. Barger, Audra K. Hernandez, Philipp Richter, Nicolas Lehner, Jane C. Charlton, Joss Blandhawthorn, Tobias Westmeier
    Abstract:

    Dynamic interactions between the two Magellanic Clouds have flung large quantities of gas into the halo of the Milky Way. The result is a spectacular arrangement of gaseous structures, including the Magellanic Stream, the Magellanic Bridge, and the Leading Arm (collectively referred to as the Magellanic System). In this third paper of a series studying the Magellanic gas in absorption, we analyze the gas ionization level using a sample of 69 Hubble Space Telescope/Cosmic Origins Spectrograph sightlines that pass through or within 30° of the 21 cm emitting regions. We find that 81% (56/69) of the sightlines show UV absorption at Magellanic velocities, indicating that the total cross-section of the Magellanic System is ≈11,000 deg{sup 2}, or around one-quarter of the entire sky. Using observations of the Si III/Si II ratio together with Cloudy photoionization modeling, we calculate the total gas mass (atomic plus ionized) of the Magellanic System to be ≈2.0 × 10{sup 9} M {sub ☉} (d/55 kpc){sup 2}, with the ionized gas contributing around three times as much mass as the atomic gas. This is larger than the current-day interstellar H I mass of both Magellanic Clouds combined, indicating that they have lost most of their initialmore » gas mass. If the gas in the Magellanic System survives to reach the Galactic disk over its Inflow time of ∼0.5-1.0 Gyr, it will represent an average Inflow Rate of ∼3.7-6.7 M {sub ☉} yr{sup –1}, potentially raising the Galactic star formation Rate. However, multiple signs of an evaporative interaction with the hot Galactic corona indicate that the Magellanic gas may not survive its journey to the disk fully intact and will instead add material to (and cool) the corona.« less

Andrew J. Fox - One of the best experts on this subject based on the ideXlab platform.

  • The COS/UVES absorption survey of the Magellanic stream. III. ionization, total mass, and Inflow Rate onto the Milky Way
    The Astrophysical Journal, 2014
    Co-Authors: Andrew J. Fox, Bart P. Wakker, Kathleen A. Barger, Audra K. Hernandez, Philipp Richter, Nicolas Lehner, Joss Bland-hawthorn, Jane C. Charlton, Tobias Westmeier, Christopher Thom
    Abstract:

    Dynamic interactions between the two Magellanic Clouds have flung large quantities of gas into the halo of the Milky Way. The result is a spectacular arrangement of gaseous structures, including the Magellanic Stream, the Magellanic Bridge, and the Leading Arm (collectively referred to as the Magellanic System). In this third paper of a series studying the Magellanic gas in absorption, we analyze the gas ionization level using a sample of 69 Hubble Space Telescope/Cosmic Origins Spectrograph sightlines that pass through or within 30° of the 21 cm emitting regions. We find that 81% (56/69) of the sightlines show UV absorption at Magellanic velocities, indicating that the total cross-section of the Magellanic System is ≈11,000 deg{sup 2}, or around one-quarter of the entire sky. Using observations of the Si III/Si II ratio together with Cloudy photoionization modeling, we calculate the total gas mass (atomic plus ionized) of the Magellanic System to be ≈2.0 × 10{sup 9} M {sub ☉} (d/55 kpc){sup 2}, with the ionized gas contributing around three times as much mass as the atomic gas. This is larger than the current-day interstellar H I mass of both Magellanic Clouds combined, indicating that they have lost most of their initialmore » gas mass. If the gas in the Magellanic System survives to reach the Galactic disk over its Inflow time of ∼0.5-1.0 Gyr, it will represent an average Inflow Rate of ∼3.7-6.7 M {sub ☉} yr{sup –1}, potentially raising the Galactic star formation Rate. However, multiple signs of an evaporative interaction with the hot Galactic corona indicate that the Magellanic gas may not survive its journey to the disk fully intact and will instead add material to (and cool) the corona.« less

  • the cos uves absorption survey of the magellanic stream iii ionization total mass and Inflow Rate onto the milky way
    The Astrophysical Journal, 2014
    Co-Authors: Andrew J. Fox, Bart P. Wakker, Kathleen A. Barger, Audra K. Hernandez, Philipp Richter, Nicolas Lehner, Jane C. Charlton, Joss Blandhawthorn, Tobias Westmeier
    Abstract:

    Dynamic interactions between the two Magellanic Clouds have flung large quantities of gas into the halo of the Milky Way. The result is a spectacular arrangement of gaseous structures, including the Magellanic Stream, the Magellanic Bridge, and the Leading Arm (collectively referred to as the Magellanic System). In this third paper of a series studying the Magellanic gas in absorption, we analyze the gas ionization level using a sample of 69 Hubble Space Telescope/Cosmic Origins Spectrograph sightlines that pass through or within 30° of the 21 cm emitting regions. We find that 81% (56/69) of the sightlines show UV absorption at Magellanic velocities, indicating that the total cross-section of the Magellanic System is ≈11,000 deg{sup 2}, or around one-quarter of the entire sky. Using observations of the Si III/Si II ratio together with Cloudy photoionization modeling, we calculate the total gas mass (atomic plus ionized) of the Magellanic System to be ≈2.0 × 10{sup 9} M {sub ☉} (d/55 kpc){sup 2}, with the ionized gas contributing around three times as much mass as the atomic gas. This is larger than the current-day interstellar H I mass of both Magellanic Clouds combined, indicating that they have lost most of their initialmore » gas mass. If the gas in the Magellanic System survives to reach the Galactic disk over its Inflow time of ∼0.5-1.0 Gyr, it will represent an average Inflow Rate of ∼3.7-6.7 M {sub ☉} yr{sup –1}, potentially raising the Galactic star formation Rate. However, multiple signs of an evaporative interaction with the hot Galactic corona indicate that the Magellanic gas may not survive its journey to the disk fully intact and will instead add material to (and cool) the corona.« less