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  • 1
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    The detectability of sea-ice leads in satellite data as a function of atmospheric conditions and measurement scale (1993)
    Cambridge University Press
    Details
    Publication Date: 1993-01-01
    Description: The release of heat from sea-ice leads is an important component of the heat budget in the Arctic, but the impact of leads on regional scale climate is difficult to assess without information on their distribution in both space and time. Remote sensing of leads using satellite data, specifically AVHRR thermal and Landsat visible imagery, is examined with respect to one lead parameter: lead width. Atmospheric effects are illustrated through the concept of thermal contrast transmittance, where the brightness temperature contrast between leads of various ice thicknesses and the surrounding multi-year ice is simulated using a radiative transfer model. Calculations are made as a function of aerosol, ice crystal precipitation, and cirrus cloud optical depths. For example, at ice crystal optical depths of more than about 1.5 under mean January conditions in the central Arctic, the brightness temperature differences between 2 m and 5 cm thick ice are similar to the ice temperature variability so that there would be insufficient contrast to distinguish a lead from the surrounding ice. The geometrical aspects of the sensor are also simulated by degrading Landsat data so that the effect of sensor field-of-view on retrieved lead width statistics can be assessed. Large leads tend to “grow” with increased pixel size while small leads disappear. Changes in lead width and orientation distributions can readily be seen.
    Print ISSN: 0260-3055
    Electronic ISSN: 1727-5644
    Topics: Geography , Geosciences
    Published by Cambridge University Press on behalf of International Glaciological Society.
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  • 2
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    Comparison and integration of ice-pack temperatures derived from AVHRR and passive microwave imagery (1993)
    Cambridge University Press
    Details
    Publication Date: 1993-01-01
    Description: Co-located sets of AVHRR and SSM/I passive microwave imagery are used to estimate ice surface temperatures and to infer cloud cover in the Arctic. Physical temperatures are determined from the AVHRR data by modeling atmospheric and surface conditions. The resulting field-of-view temperatures are converted to ice surface skin temperatures by adjusting for ice concentration calculated using the SSM/I data. By selecting AVHRR-derived temperatures for clear sky conditions, “effective” emissivities of first-year and multi-year ice are calculated. Given these emissivities, microwave brightness temperatures, and proportions of first-year and multi-year ice as estimated using the NASA Team Algorithm, physical temperatures of the sea ice/snow surface are calculated that are, in theory, relatively independent of cloud conditions. The resulting ice temperatures are used to delineate a portion of the cloud cover in the AVHRR data. The advantages of this approach are that only a fairly small amount of AVHRR data are needed to calibrate the SSM/I imagery that can then be used to calculate a time-series of temperatures on a large scale.
    Print ISSN: 0260-3055
    Electronic ISSN: 1727-5644
    Topics: Geography , Geosciences
    Published by Cambridge University Press on behalf of International Glaciological Society.
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  • 3
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    Snow and ice applications of AVHRR in polar regions: report of a workshop held in Boulder, Colorado, 20 May 1992 (1993)
    Cambridge University Press
    Details
    Publication Date: 1993-01-01
    Description: The third symposium on Remote Sensing of Snow and Ice, organized by the International Glaciological Society, took place in Boulder, Colorado, 17–22 May 1992. As part of this meeting a total of 21 papers was presented on snow and ice applications of Advanced Very High Resolution Radiometer (AVHRR) satellite data in polar regions. Also during this meeting a NASA sponsored Workshop was held to review the status of polar surface measurements from AVHRR. In the following we have summarized the ideas and recommendations from the workshop, and the conclusions of relevant papers given during the regular symposium sessions. The seven topics discussed include cloud masking, ice surface temperature, narrow-band albedo, ice concentration, lead statistics, sea-ice motion and ice-sheet studies with specifics on applications, algorithms and accuracy, following recommendations for future improvements. In general, we can affirm the strong potential of AVHRR for studying sea ice and snow covered surfaces, and we highly recommend this satellite data set for long-term monitoring of polar process studies. However, progress is needed to reduce the uncertainty of the retrieved parameters for all of the above mentioned topics to make this data set useful for direct climate applications such as heat balance studies and others. Further, the acquisition and processing of polar AVHRR data must become better coordinated between receiving stations, data centers and funding agencies to guarantee a long-term commitment to the collection and distribution of high quality data.
    Print ISSN: 0260-3055
    Electronic ISSN: 1727-5644
    Topics: Geography , Geosciences
    Published by Cambridge University Press on behalf of International Glaciological Society.
    Location Call Number Expected Availability
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    PAPER CURRENT
  • 4
    facet.materialart.
    Unknown
    Comparison and integration of ice-pack temperatures derived from AVHRR and passive microwave imagery (1993)
    Cambridge University Press
    Details
    Publication Date: 1993-01-01
    Description: Co-located sets of AVHRR and SSM/I passive microwave imagery are used to estimate ice surface temperatures and to infer cloud cover in the Arctic. Physical temperatures are determined from the AVHRR data by modeling atmospheric and surface conditions. The resulting field-of-view temperatures are converted to ice surface skin temperatures by adjusting for ice concentration calculated using the SSM/I data. By selecting AVHRR-derived temperatures for clear sky conditions, “effective” emissivities of first-year and multi-year ice are calculated. Given these emissivities, microwave brightness temperatures, and proportions of first-year and multi-year ice as estimated using the NASA Team Algorithm, physical temperatures of the sea ice/snow surface are calculated that are, in theory, relatively independent of cloud conditions. The resulting ice temperatures are used to delineate a portion of the cloud cover in the AVHRR data. The advantages of this approach are that only a fairly small amount of AVHRR data are needed to calibrate the SSM/I imagery that can then be used to calculate a time-series of temperatures on a large scale.
    Print ISSN: 0260-3055
    Electronic ISSN: 1727-5644
    Topics: Geography , Geosciences
    Published by Cambridge University Press on behalf of International Glaciological Society.
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    PAPER CURRENT
  • 5
    facet.materialart.
    Unknown
    The detectability of sea-ice leads in satellite data as a function of atmospheric conditions and measurement scale (1993)
    Cambridge University Press
    Details
    Publication Date: 1993-01-01
    Description: The release of heat from sea-ice leads is an important component of the heat budget in the Arctic, but the impact of leads on regional scale climate is difficult to assess without information on their distribution in both space and time. Remote sensing of leads using satellite data, specifically AVHRR thermal and Landsat visible imagery, is examined with respect to one lead parameter: lead width. Atmospheric effects are illustrated through the concept of thermal contrast transmittance, where the brightness temperature contrast between leads of various ice thicknesses and the surrounding multi-year ice is simulated using a radiative transfer model. Calculations are made as a function of aerosol, ice crystal precipitation, and cirrus cloud optical depths. For example, at ice crystal optical depths of more than about 1.5 under mean January conditions in the central Arctic, the brightness temperature differences between 2 m and 5 cm thick ice are similar to the ice temperature variability so that there would be insufficient contrast to distinguish a lead from the surrounding ice. The geometrical aspects of the sensor are also simulated by degrading Landsat data so that the effect of sensor field-of-view on retrieved lead width statistics can be assessed. Large leads tend to “grow” with increased pixel size while small leads disappear. Changes in lead width and orientation distributions can readily be seen.
    Print ISSN: 0260-3055
    Electronic ISSN: 1727-5644
    Topics: Geography , Geosciences
    Published by Cambridge University Press on behalf of International Glaciological Society.
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    PAPER CURRENT
  • 6
    facet.materialart.
    Unknown
    Snow and ice applications of AVHRR in polar regions: report of a workshop held in Boulder, Colorado, 20 May 1992 (1993)
    Cambridge University Press
    Details
    Publication Date: 1993-01-01
    Description: The third symposium on Remote Sensing of Snow and Ice, organized by the International Glaciological Society, took place in Boulder, Colorado, 17–22 May 1992. As part of this meeting a total of 21 papers was presented on snow and ice applications of Advanced Very High Resolution Radiometer (AVHRR) satellite data in polar regions. Also during this meeting a NASA sponsored Workshop was held to review the status of polar surface measurements from AVHRR. In the following we have summarized the ideas and recommendations from the workshop, and the conclusions of relevant papers given during the regular symposium sessions. The seven topics discussed include cloud masking, ice surface temperature, narrow-band albedo, ice concentration, lead statistics, sea-ice motion and ice-sheet studies with specifics on applications, algorithms and accuracy, following recommendations for future improvements. In general, we can affirm the strong potential of AVHRR for studying sea ice and snow covered surfaces, and we highly recommend this satellite data set for long-term monitoring of polar process studies. However, progress is needed to reduce the uncertainty of the retrieved parameters for all of the above mentioned topics to make this data set useful for direct climate applications such as heat balance studies and others. Further, the acquisition and processing of polar AVHRR data must become better coordinated between receiving stations, data centers and funding agencies to guarantee a long-term commitment to the collection and distribution of high quality data.
    Print ISSN: 0260-3055
    Electronic ISSN: 1727-5644
    Topics: Geography , Geosciences
    Published by Cambridge University Press on behalf of International Glaciological Society.
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    PAPER CURRENT
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