Radar Observer

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D Schertzer - One of the best experts on this subject based on the ideXlab platform.

  • scalar multifractal Radar Observer s problem
    Journal of Geophysical Research, 1996
    Co-Authors: S Lovejoy, M R Duncan, D Schertzer
    Abstract:

    The classical Radar Observer's problem in rain is to interpret the fluctuating Radar echo from precipitation. Contrary to the usual homogeneity assumption involving Poisson statistics and incoherent scattering, we make a (scaling) heterogeneity assumption involving multifractal statistics and (some) coherent scattering. We consider the simplest problem, which is to relate the liquid water (σ) statistics to the (measured) effective Radar reflectivity statistics (Ze) and to the (theoretical) Radar reflectivity factor (Z; Ze =Z for incoherent scattering). We ignore polarization effects (that is, we use the scalar wave approximation), and denote the pulse length l, wavelength λw, the inner (homogeneity) scale of the rain field (η), and the outer (largest) scale of rain (L). For the simplest (conservative) multifractal σ the two main effects are 1) as in the standard theory, Z ≈ σ2; however, because of the strong subpulse volume gradients, there is a bias of (l/λww)Kσ(2);(Kσ(2) is the scaling exponent of σ2); 2) because of partial coherence, there is an enhancement: Ze/Z ≈ (λw/η(D-Kσ(2) where D is the (effective) dimension of space. For nonconservative multifractals (parametrized by H) we obtain the overall bias in the means: / ≈ (λw/η)D-Kσ(2)(L/λw)−2H. Using available data, we estimated this as typically ≈10−3 which is ≪1; Z should therefore not be used as a proxy for Ze. New theories relating Radar measurements to rain must therefore be developed. Finally, we show that Radar “speckle” (the drop “rearrangement” problem) is a general consequence of multifractal liquid water/ drop correlations.

S Lovejoy - One of the best experts on this subject based on the ideXlab platform.

  • scalar multifractal Radar Observer s problem
    Journal of Geophysical Research, 1996
    Co-Authors: S Lovejoy, M R Duncan, D Schertzer
    Abstract:

    The classical Radar Observer's problem in rain is to interpret the fluctuating Radar echo from precipitation. Contrary to the usual homogeneity assumption involving Poisson statistics and incoherent scattering, we make a (scaling) heterogeneity assumption involving multifractal statistics and (some) coherent scattering. We consider the simplest problem, which is to relate the liquid water (σ) statistics to the (measured) effective Radar reflectivity statistics (Ze) and to the (theoretical) Radar reflectivity factor (Z; Ze =Z for incoherent scattering). We ignore polarization effects (that is, we use the scalar wave approximation), and denote the pulse length l, wavelength λw, the inner (homogeneity) scale of the rain field (η), and the outer (largest) scale of rain (L). For the simplest (conservative) multifractal σ the two main effects are 1) as in the standard theory, Z ≈ σ2; however, because of the strong subpulse volume gradients, there is a bias of (l/λww)Kσ(2);(Kσ(2) is the scaling exponent of σ2); 2) because of partial coherence, there is an enhancement: Ze/Z ≈ (λw/η(D-Kσ(2) where D is the (effective) dimension of space. For nonconservative multifractals (parametrized by H) we obtain the overall bias in the means: / ≈ (λw/η)D-Kσ(2)(L/λw)−2H. Using available data, we estimated this as typically ≈10−3 which is ≪1; Z should therefore not be used as a proxy for Ze. New theories relating Radar measurements to rain must therefore be developed. Finally, we show that Radar “speckle” (the drop “rearrangement” problem) is a general consequence of multifractal liquid water/ drop correlations.

M R Duncan - One of the best experts on this subject based on the ideXlab platform.

  • scalar multifractal Radar Observer s problem
    Journal of Geophysical Research, 1996
    Co-Authors: S Lovejoy, M R Duncan, D Schertzer
    Abstract:

    The classical Radar Observer's problem in rain is to interpret the fluctuating Radar echo from precipitation. Contrary to the usual homogeneity assumption involving Poisson statistics and incoherent scattering, we make a (scaling) heterogeneity assumption involving multifractal statistics and (some) coherent scattering. We consider the simplest problem, which is to relate the liquid water (σ) statistics to the (measured) effective Radar reflectivity statistics (Ze) and to the (theoretical) Radar reflectivity factor (Z; Ze =Z for incoherent scattering). We ignore polarization effects (that is, we use the scalar wave approximation), and denote the pulse length l, wavelength λw, the inner (homogeneity) scale of the rain field (η), and the outer (largest) scale of rain (L). For the simplest (conservative) multifractal σ the two main effects are 1) as in the standard theory, Z ≈ σ2; however, because of the strong subpulse volume gradients, there is a bias of (l/λww)Kσ(2);(Kσ(2) is the scaling exponent of σ2); 2) because of partial coherence, there is an enhancement: Ze/Z ≈ (λw/η(D-Kσ(2) where D is the (effective) dimension of space. For nonconservative multifractals (parametrized by H) we obtain the overall bias in the means: / ≈ (λw/η)D-Kσ(2)(L/λw)−2H. Using available data, we estimated this as typically ≈10−3 which is ≪1; Z should therefore not be used as a proxy for Ze. New theories relating Radar measurements to rain must therefore be developed. Finally, we show that Radar “speckle” (the drop “rearrangement” problem) is a general consequence of multifractal liquid water/ drop correlations.

Nicholas C. Everhart - One of the best experts on this subject based on the ideXlab platform.

  • Information Flow and Development of Coordination in Distributed Supervisory Control Teams
    International Journal of Human-computer Interaction, 1998
    Co-Authors: Barrett S. Caldwell, Nicholas C. Everhart
    Abstract:

    This article presents results of a study to examine the flow of information between members of a new task team conducting a distributed supervisory control task. The emphasis of this project was on the effects of information presentation and message transmission delays on the development of effective information flow among human operators. The project focused on the earliest stages of team performance to explore how teams begin to refine distributed task coordination. The task simulation used in this project was a distributed navigation task based on a commercially available computer game (Spectre VRTM). Teams of three ("out the window" [OTW] Observer, "long-range Radar" Observer, and a driver without direct visual information) were required to navigate a vehicle in a dynamic and potentially hostile environment containing obstacles and moving hazards. The goal of the task was to accumulate points through capturing flags. Information presentation was manipulated through standard game selections of wirefram...

Barrett S. Caldwell - One of the best experts on this subject based on the ideXlab platform.

  • Information Flow and Development of Coordination in Distributed Supervisory Control Teams
    International Journal of Human-computer Interaction, 1998
    Co-Authors: Barrett S. Caldwell, Nicholas C. Everhart
    Abstract:

    This article presents results of a study to examine the flow of information between members of a new task team conducting a distributed supervisory control task. The emphasis of this project was on the effects of information presentation and message transmission delays on the development of effective information flow among human operators. The project focused on the earliest stages of team performance to explore how teams begin to refine distributed task coordination. The task simulation used in this project was a distributed navigation task based on a commercially available computer game (Spectre VRTM). Teams of three ("out the window" [OTW] Observer, "long-range Radar" Observer, and a driver without direct visual information) were required to navigate a vehicle in a dynamic and potentially hostile environment containing obstacles and moving hazards. The goal of the task was to accumulate points through capturing flags. Information presentation was manipulated through standard game selections of wirefram...