Caractérisation de la neige, du névé et de la glace par traitement d'images.
It is now recognized that human activities , by the extent they have achieved since the industrial era, are likely to alter the Earth's climate (IPCC, 1996). Paleo climate and the climate change models show that the polar caps are particularly sensitive to global climate change. They are more l...
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| Other Authors: | , , , , , , |
| Format: | Doctoral or Postdoctoral Thesis |
| Language: | French |
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HAL CCSD
1999
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| Subjects: | |
| Online Access: | https://theses.hal.science/tel-00930144 https://theses.hal.science/tel-00930144/document https://theses.hal.science/tel-00930144/file/1999_Michel_Gay_Th.pdf |
| Summary: | It is now recognized that human activities , by the extent they have achieved since the industrial era, are likely to alter the Earth's climate (IPCC, 1996). Paleo climate and the climate change models show that the polar caps are particularly sensitive to global climate change. They are more likely to play an important role but unknown on the sea level. The positive term of mass balance of polar ice sheets is the accumulation of snow, whereas the negative term is formed by the flow of ice into the oceans . The size of the polar ice caps and their hostile environment limit the amount of available field data . Only satellite remote sensing is able to provide information on geographical scales as large as Antarctica or the Arctic and allows regular monitoring over time. But to be easily interpreted, in order to deduce the snowpack characteristics observed from space (size, shape of grains, surface roughness . ), satellite data should be validated and inverted using simplified parameters . Prior to the establishment of these relations, it is necessary to develop a snow reflectance model ( thesis C. Leroux 1996) taking into account the physical and optical characteristics of the snow, and a microwave emissivity model (thesis Surdyck S. 1993) that provide volume information on the morphology of the snowpack. The snowpack is characterized by several physical parameters that depend on the depth: temperature, density , size and shape of grains mainly . It is therefore essential to establish a robust and simple parameterization of the size and shape of snow grains from their observation. Image processing allows to establish these relationships and allows automatic processing of a large number of data independent of the observer. Another glaciological problem of firn is the interpretation of data obtained from the analysis of trapped air bubbles in the gas . This study implies, in particular , the dating of the ice in the firn at the close off, is necessary to determine the age of gas with respect to the ice age. Dating ... |
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