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  • 1985-1989  (5)
  • 1
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    A two-scale Bragg scattering model for microwave backscatter from wind generated waves (1986)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: A model for the wavenumber spectrum for fully developed seas is derived as a function of the mean wind gradient. The high wavenumber part of the spectrum, which defines the Bragg wavenumbers, is an equilibrium spectrum in balance by a wind forcing term determined by viscous dissipation, which is a strong function of water temperature, and dissipation by breaking and microbreaking. The low wavenumber spectrum, constructed from surface elevation observations of gravity waves, is merged with the high wavenumber spectrum. Parameters are adjusted to fit circle flight data for Ku-band. The full spectrum is used in the two-scale Bragg scattering theory, plus specular reflection, to compute backscatter as a function of wind speed, direction, incidence angle, and water temperature (which determines viscosity) for Ku-band.
    Keywords: OCEANOGRAPHY
    Type: ESA Proceedings of the 1986 International Geoscience and Remote Sensing Symposium (IGARSS '86) on Remote Sensing: Today's Solutions for Tomorrow's Information Needs, Volume 1; p 291-296
    Format: text
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    NASA TECHNICAL REPORTS
  • 2
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    Verification results for a two-scale model of microwave backscatter from the sea surface (1986)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: The backscatter model of Donelan and Pierson (1986) was adjusted to fit Ku-Band at 13.9 GHz. Data from L to Ka-band are used to test the model. In general, there is no power law. When the wind drops below certain threshold speeds there may be no detectable Bragg backscatter. Saturation may occur at high winds. Results from the Seasat-SASS are used to substantiate the predictions of the model. Suggestions for experiments for determining the overall validity of the model are made.
    Keywords: OCEANOGRAPHY
    Type: ESA Proceedings of the 1986 International Geoscience and Remote Sensing Symposium (IGARSS '86) on Remote Sensing: Today's Solutions for Tomorrow's Information Needs, Volume 1; p 297-302
    Format: text
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  • 3
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    Oceanographic and meteorological research based on the data products of SEASAT (1985)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: Reservations were expressed concerning the sum of squares wind recovery algorithm and the power law model function. The SAS sum of squares (SOS) method for recovering winds from backscatter data leads to inconsistent results when V pol and H pol winds are compared. A model function that does not use a power law and that accounts for sea surface temperature is needed and is under study both theoretically and by means of the SASS mode 4 data. Aspects of the determination of winds by means of scatterometry and of the utilization of vector wind data for meteorological forecasts are elaborated. The operational aspect of an intermittent assimilation scheme currently utilized for the specification of the initial value field is considered with focus on quantifying the absolute 12-hour linear displacement error of the movement of low centers.
    Keywords: EARTH RESOURCES AND REMOTE SENSING
    Type: E85-10091 , NASA-CR-175526 , NAS 1.26:175526
    Format: application/pdf
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  • 4
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    The closure problem for turbulence in meteorology and oceanography (1985)
    In:  Other Sources
    Details
    Publication Date: 2019-07-12
    Description: The dependent variables used for computer based meteorological predictions and in plans for oceanographic predictions are wave number and frequency filtered values that retain only scales resolvable by the model. Scales unresolvable by the grid in use become 'turbulence'. Whether or not properly processed data are used for initial values is important, especially for sparce data. Fickian diffusion with a constant eddy diffusion is used as a closure for many of the present models. A physically realistic closure based on more modern turbulence concepts, especially one with a reverse cascade at the right times and places, could help improve predictions.
    Keywords: GEOSCIENCES (GENERAL)
    Type: PCH/PhysicoChemical Hydrodynamics (ISSN 0191-9059); 6; 5-6
    Format: text
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  • 5
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    Aspects of the determination of winds by means of scatterometry and of the utilization of vector wind data for meteorological forecasts (1986)
    In:  Other Sources
    Details
    Publication Date: 2019-07-12
    Description: The present paper provides a description of four aspects of scatterometer winds and their uses. The theory of wave generation by the wind is considered along with an analysis of the properties of superobservations, and studies of intermittent versus continuous data assimilation methods for numerical weather predictions which use remotely sensed data. A comparison of the sum of squares versus the maximum likelihood method for recovering the vector winds is also conducted. Questions regarding wind speed, friction velocity, or normal stress are discussed and synoptic scale fields from Seasat-SASS data are examined.
    Keywords: METEOROLOGY AND CLIMATOLOGY
    Type: Journal of Geophysical Research (ISSN 0148-0227); 91; 2263-227
    Format: text
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