Science Service System

Summary of Proposal HYD0998

TitleEvaluation of snow characteristics in a subarctic region using multi-polarizated and multi-frequency SAR data
Investigator Bernier, Monique - INRS, Eau, Terre et Environnement
Team Member
Mr. Duguay, Yannick - Institut national de la recherche scientifique (INRS), Centre Eau Terre Environnement (ETE)
Prof. Ludwig, Ralf - Ludwig-Maximilians University (LMU), Geography
Mrs. May, Inga - Ludwig-Maximilians University (LMU), Geography
SummaryThis project is part of an international research collaboration between INRS in Quebec city, LMU in Munich and Université Laval in Quebec city. The aim of this collaboration is to develop a monitoring system based on remote sensing data and GIS-based data analysis to model the permafrost dynamics in a context of climate changes. It has been demonstrated that snow cover plays an important role on the freeze up and thawing cycle of the permafrost's active layer [1]. The mapping of snow characteristics therefore becomes an important part of any attempts to model permafrost dynamics. In-situ measurements for the purpose of snow mapping are tedious and can be expensive, especially in northern regions. Previous studies have shown the potential of multi-polarized and multi-frequency SAR data to estimate snow cover parameters [2, 3]. The objective of this study is to measure snow cover characteristics (depth, density, Snow Water Equivalent) using polarimetric C-band SAR data as well as multi-polarized X-band data. The recent availability of platforms operating in X and C bands and offering multiple polarizations opens up new possibilities for snow characteristics retrieval. The C-band, with its longer wavelength, is almost unaffected by dry snow and can measure the effect of the snowpack on the underlying soil electromagnetic scattering. The shorter wavelength of TerraSAR-X will provide information on the volume scattering of the snow cover. The study area situated in the vicinity of the Umiujaq village in northern Quebec, Canada (56.55° N, 76.55° O). TerraSAR-X data acquisitions would be performed during the 2011 and 2012 winters and reference images will be needed in the fall of 2011 to compare the signal between the winter data and snow-free conditions. These acquisitions would be in coordination with RADARSAT-2 acquisitions for the 2011 winter. Field campaigns are to be carried out during the data acquisitions to measure snow density and depths over selected sample sites covering various terrain types. The winter acquisitions are needed during the months of March and April, when the snow cover reaches its maximum depth and is relatively dry. Two series of dual-polarized (VV-VH) images are to be acquired at different incidence angle. At low incidence angles, the backscattered signal from a dry snow covered surface is dominated by surface scattering, while at higher incidence angles the signal becomes more sensitive to the volume scattering from the snowpack. The combination of the co-polarized and cross-polarized signals can bring further information on the volume scattering through parameters such as the depolarization factor (VH/VV). Information on vegetation and soil characteristics will also be used to take their effect into account in the final algorithm. The final algorithm will integrate a multi-temporal approach comparing the snow-free conditions of the fall with the winter conditions. A discrimination of different vegetation and soil types will also be integrated to consider snow accumulation patterns on various environments. The final product will be an algorithm to retrieve snow characteristics using multifrequency and multipolarized SAR data combined with soil and vegetation information. References: [1] L. E. Goodrich, "The influence of snow cover on the ground thermal regime," Canadian Geotechnical Journal, vol. 19, pp. 421-432, November 1982 1982. [2] J. C. Shi and J. Dozier, "Estimation of snow water equivalence using SIR-C/X-SAR, part II: Inferring snow depth and particle size," Ieee Transactions on Geoscience and Remote Sensing, vol. 38, pp. 2475-2488, Nov 2000. [3] J. R. Kendra, K. Sarabandi, and F. T. Ulaby, "Radar measurements of snow: Experiment and analysis," Ieee Transactions on Geoscience and Remote Sensing, vol. 36, pp. 864-879, May 1998.

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