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  • 1
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    Does the scatterometer see wind speed or friction velocity? (1984)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: Studies of radar backscatter from the sea surface are referred either to the wind speed, U, or friction velocity, u(sub *). Bragg scattering theory suggests that these variations in backscatter are directly related to the height of the capillary-gravity waves modulated by the larger waves in tilt and by straining of the short wave field. The question then arises as to what characteristic of the wind field is most probably correlated with the wave number spectrum of the capillary-gravity waves. The justification for selecting U as the appropriate meteorological parameter to be associated with backscatter from L-band to Ku-band are reviewed. Both theoretical reasons and experimental evidence are used to demonstrate that the dominant parameter is U/C(lambda) where U is the wind speed at a height of about lambda/2 for waves having a phase speed of C(lambda).
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA. Marshall Space Flight Center Frontiers of Remote Sensing of the Oceans and Troposphere from Air and Space Platforms; p 75-87
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 2
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    Synoptic scale wind field properties from the SEASAT SASS (1984)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: Dealiased SEASAT SEASAT A Scatterometer System SASS vector winds obtained during the Gulf Of Alaska SEASAT Experiment GOASEX program are processed to obtain superobservations centered on a one degree by one degree grid. The grid. The results provide values for the combined effects of mesoscale variability and communication noise on the individual SASS winds. These superobservations winds are then processed further to obtain estimates of synoptic scale vector winds stress fields, the horizontal divergence of the wind, the curl of the wind stress and the vertical velocity at 200 m above the sea surface, each with appropriate standard deviations of the estimates for each grid point value. They also explain the concentration of water vapor, liquid water and precipitation found by means of the SMMR Scanning Multichannel Microwave Radiometer at fronts and occlusions in terms of strong warm, moist air advection in the warm air sector accompanied by convergence in the friction layer. Their quality is far superior to that of analyses based on conventional data, which are shown to yield many inconsistencies.
    Keywords: EARTH RESOURCES AND REMOTE SENSING
    Type: E84-10169 , NASA-CR-3810 , NAS 1.26:3810
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 3
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    Vector wind, horizontal divergence, wind stress and wind stress curl from SEASAT-SASS at one degree resolution (1984)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: Conventional data obtained in 1983 are contrasted with SEASAT-A scatterometer and scanning multichannel microwave radiometer (SMMR) data to show how observations at a single station can be extended to an area of about 150,000 square km by means of remotely sensed data obtained in nine minutes. Superobservations at a one degree resolution for the vector winds were estimated along with their standard deviations. From these superobservations, the horizontal divergence, vector wind stress, and the curl of the wind stress can be found. Weather forecasting theory is discussed and meteorological charts of the North Pacific Ocean are presented. Synoptic meteorology as a technique is examined.
    Keywords: METEOROLOGY AND CLIMATOLOGY
    Type: NASA. Marshall Space Flight Center Frontiers of Remote Sensing of the Oceans and Troposphere from Air and Space Platforms; p 557-566
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 4
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    A Monte Carlo comparison of the recovery of winds near upwind and downwind from the SASS-1 model function by means of the sum of squares algorithm and a maximum likelihood estimator (1984)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: Backscatter measurements at upwind and crosswind are simulated for five incidence angles by means of the SASS-1 model function. The effects of communication noise and attitude errors are simulated by Monte Carlo methods, and the winds are recovered by both the Sum of Square (SOS) algorithm and a Maximum Likelihood Estimater (MLE). The SOS algorithm is shown to fail for light enough winds at all incidence angles and to fail to show areas of calm because backscatter estimates that were negative or that produced incorrect values of K sub p greater than one were discarded. The MLE performs well for all input backscatter estimates and returns calm when both are negative. The use of the SOS algorithm is shown to have introduced errors in the SASS-1 model function that, in part, cancel out the errors that result from using it, but that also cause disagreement with other data sources such as the AAFE circle flight data at light winds. Implications for future scatterometer systems are given.
    Keywords: EARTH RESOURCES AND REMOTE SENSING
    Type: NASA-CR-3839 , NAS 1.26:3839
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 5
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    The measurement of the synoptic scale wind over the ocean (1983)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: The effects of mesoscale and microscale fluctuations of the winds on the determination of the synoptic scale wind are studied in order to show the effects of mesoscale variability on the verification of wind forecasts and on the comparison of remotely sensed and anemometer-averaged winds, and to show how to measure the synoptic wind scale more accurately. The frequencies involved correspond to periods longer than one hour and extend to the microscale. Nondimensional spectra that span both the mesoscale and the microscale are derived. Both conventional anemometer averages and remotely sensed winds contain a random component of the mesoscale wind in their values. These components are differences and not errors when winds are compared, and quantitative values for these differences are given. Ways of improving the measurement of the synoptic scale wind by transient ships, data buoys, and scatterometers on future spacecraft are described.
    Keywords: METEOROLOGY AND CLIMATOLOGY
    Type: Journal of Geophysical Research; 88; Feb. 28
    Format: text
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    NASA TECHNICAL REPORTS
  • 6
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    Highlights of the SEASAT-SASS program - A review (1983)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: Some important concepts of the SEASAT-SASS program are described and some of the decisions made during the program as to methods for relating wind to backscatter are discussed. The radar scatterometer design is analyzed along with the model function, which is an empirical relationship between the backscatter value and the wind speed, wind direction, and incidence angle of the radar beam with the sea surface. The results of Monte Carlo studies of mesoscale turbulence and of studies of wind stress on the sea surface involving SASS are reviewed.
    Keywords: SPACECRAFT INSTRUMENTATION
    Format: text
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