Duguay, Yannick; Bernier, Monique; Dominé, Florent; Lévesque, Esther
(2013).
Monitoring subarctic environments using x- and c-band radar imagery.
In: ArcticNet Annual Scientific meeting - ASM 2013, 9-13 décembre 2013, Halifax, Canada.
Résumé
Subarctic environments are signifi cantly aff ected by
the climate warming observed in recent decades. Th ese
perturbations lead to many environmental changes such as
permafrost thawing and expansion of shrub vegetation cover.
Snow, with its insulating properties, also plays an important
role in these processes maintaining relatively warm ground
temperatures during the winter while protecting the vegetation
from the cold and wind. Th e presence of shrubs may, in turn,
trap wind blown snow and creates a positive feedback favoring
the expansion of shrub vegetation at the expense of the tundra.
Th e objective of this study is to develop methods for monitoring
simultaneous subarctic environments of these two elements to
ensure eff ective monitoring of subarctic environments. Satellite
Synthetic Aperture Radar (SAR) allow, among other things,
provide information on the vertical structure of the observed
objects and are considered here to estimate the height of the
vegetation and snow cover thickness.
Th e study area is a 60 km2
region situated around the
Umiujaq community (56.55° N, 76.55° W) in northern
Quebec, Canada. Th e area can be divided into two distinct
environments: the coastal region to the east and the Lac
Guillaume-Delisle graben to the west. Th e vegetation in the
coastal region is very sporadic and dominated by tundra
vegetation, while the graben vegetation is mainly shrublands
with patches of conifers. A series of polarimetric RADARSAT-2
C-band images (HH, VV, HV, VH polarizations) and dualpolarized
TerraSAR-X X-band images (HH, HV polarizations)
have been acquired over the area between October 2011
and April 2012 during the fall and winter seasons. Field
measurement campaigns where performed during the summer
of 2009 and the winter of 2012 to collect data on the vegetation
and snow characteristics respectively. Temperature and soil
moisture sensors were also installed at 6 selected sampling sites.
In-situ observations have shown that the height of the shrub
vegetation infl uences the depth of the snow cover. Preliminary
results show an increase in the RADARSAT-2 backscattering
with vegetation height while the TerraSAR-X backscattering
seems to saturate with higher vegetation. Th e fall images,
representing the baseline without snow cover, are then compared
with the winter images to evaluate the eff ect of snow cover on
the SAR signal. In the presence of snow, RADARSAT-2 signal
is attenuated while the TerraSAR-X signal increases slightly.
Th e relationship between snow depth and radar parameters
is relatively weak. A fi rst classifi cation with and unsupervised
Wishart method was performed using the polarimetric
RADARSAT-2 data to delineate vegetated areas and allowed
to classify three types of vegetation. Given the correlation
between the heights of vegetation and snow cover, improved
segmentation based on the height of the shrub cover should
allow a better estimation of the snow cover parameters.
Type de document: |
Document issu d'une conférence ou d'un atelier
|
Informations complémentaires: |
Affiche |
Mots-clés libres: |
environnement subarctique; végétation; neige; imagerie radar; surveillance |
Centre: |
Centre Eau Terre Environnement |
Date de dépôt: |
12 nov. 2020 14:59 |
Dernière modification: |
12 nov. 2020 14:59 |
URI: |
http://espace.inrs.ca/id/eprint/4051 |
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