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  • 1
    Publication Date: 2011-08-17
    Description: The measured time between the transmission and rzturn of 13.9 GHz radar pulses from the GEOS 3 satellite (at a mean altitude of 844.5 km and an inclination of 114 deg 52 min) is used to determine the thickness of the Greenland ice cap, with an accuracy in surface elevation on the order of 2 m. Attention is given to changes in ice thickness as an indicator of climatic change in general, and change in mean sea level in particular. Each elevation data point obtained by the satellite represents an average along 0.67 km of ground track, and three-dimensional maps are presented to illustrate the data.
    Keywords: EARTH RESOURCES AND REMOTE SENSING
    Type: Nature; 274; Aug. 10
    Format: text
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  • 2
    Publication Date: 2019-01-25
    Description: The rate of net accumulation at the surface and its distribution in ice sheet areas bounded by the dry snow line may be approximated by a determination of either firn external emissivity or various other emissivity terms. A compilation of mean annual brightness temperature for the Greenland ice sheet based on Nimbus-5 Electrically Scanning Microwave Radiometer (19 GHz) data is used to approximate the distribution of the accumulation rate in the area bounded by the dry snow line, applying a simple conversion involving a polynomial function. This is compared with a compilation produced elsewhere using Nimbus-6 SCAMS (31 GHz) data, applying a complex conversion involving the temperature dependence of the absorption coefficient, and with the latest compilation based on surface measurements of the accumulation rate. The findings indicate that in Greenland, the use of polynomial functions to convert for net surface accumulation is a reliable and simple method for estimating both the rate of accumulation and its distribution in areas where there is no melting at the surface.
    Keywords: EARTH RESOURCES AND REMOTE SENSING
    Type: Calgary Univ., Proceedings of the 14th Canadian Symposium on Remote Sensing; p 502-507
    Format: text
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  • 3
    Publication Date: 2019-06-28
    Description: A field of measured anomalies of some physical variable relative to their time averages, is partitioned in either the space domain or the time domain. Eigenvectors and corresponding principal components of the smaller dimensioned covariance matrices associated with the partitioned data sets are calculated independently, then joined to approximate the eigenstructure of the larger covariance matrix associated with the unpartitioned data set. The accuracy of the approximation (fraction of the total variance in the field) and the magnitudes of the largest eigenvalues from the partitioned covariance matrices together determine the number of local EOF's and principal components to be joined by any particular level. The space-time distribution of Nimbus-5 ESMR sea ice measurement is analyzed.
    Keywords: EARTH RESOURCES AND REMOTE SENSING
    Type: NASA-TM-83916 , NAS 1.15:83916
    Format: application/pdf
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  • 4
    Publication Date: 2019-06-28
    Description: Temporal variations of the brightness temperature of selected regions representing ocean, sea ice, and ice sheets were studied. Shifts that could not be ascribed to geophysical effects were found to occur during the same periods in the various regions. The procedures employed to correct for these shifts are described.
    Keywords: EARTH RESOURCES AND REMOTE SENSING
    Type: NASA-TM-82055
    Format: application/pdf
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  • 5
    Publication Date: 2019-06-28
    Description: A summary data set concerning 4 years of Antarctic sea-ice conditions was created and is available on magnetic tape. The data were derived from electrically scanning microwave radiometer brightness temperatures and were mapped into a polar stereographic grid enclosing the 50 deg S latitude circle. The grid size varies from about 32 by 32 sq km at the poles to about 28 by 28 sq km at 50 deg S. The microwave brightness temperatures of Antarctic sea ice are predominantly characteristic of first-year ice with an emissivity of 0.92 at 19 GHz frequency. Sea ice concentrations were calculated from the brightness temperature data for each grid element with an algorithm that uses an emissivity value of 0.92 and an ice physical temperature estimate from climatological surface air temperatures. Monthly, multiyear monthly, and yearly maps of brightness temperatures and sea ice concentrations were created for the 4 years, except for 7 months for which useable data were insufficient.
    Keywords: EARTH RESOURCES AND REMOTE SENSING
    Type: NASA-TM-83812
    Format: application/pdf
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  • 6
    Publication Date: 2019-06-27
    Description: The microwave brightness temperature for snow fields was studied assuming that the snow cover consists of closely packed scattering spheres which do not interact coherently. The Mie scattering theory was used to compute the volume scattering albedo. It is shown that in the wavelength range from 0.8 to 2.8 cm, most of the micro-radiation emanates from a layer 10 meters or less in thickness. It is concluded that it is possible to determine snow accumulation rates as well as near-surface temperature.
    Keywords: EARTH RESOURCES AND REMOTE SENSING
    Type: NASA-TM-X-70871 , X-910-75-36
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  • 7
    Publication Date: 2019-07-13
    Description: Glaciological applications of a satellite laser altimeter system with a range precision of approximately 10 cm and a footprint diameter of 70 m are discussed. Available data on ice-sheet dynamics are reviewed, and the measurement errors associated with the laser altimeter are examined. It is shown that information collected with the system could make it possible to detect changes in average elevation (i.e., in average ice thickness) of less than 15 cm for areas of hundreds of sq km to a few thousand sq km. Other possible applications of the system are briefly considered, including the mapping of the positions of ice-sheet margins, the mapping of the junction between a grounded ice sheet and a floating ice shelf, and the estimation of iceberg calving rates.
    Keywords: EARTH RESOURCES AND REMOTE SENSING
    Type: International Geoscience and Remote Sensing Symposium; Jun 08, 1981 - Jun 10, 1981; Washington, DC
    Format: text
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