Potential of C and X Band SAR for Shrub Growth Monitoring in Sub-Arctic Environments

Duguay, Yannick; Bernier, Monique; Lévesque, Esther; Tremblay, Benoı̂t

doi:10.3390/rs70709410

Cited by 42 publications

(43 citation statements)

References 40 publications

(32 reference statements)

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Fresh vegetation canopy can increase the fraction of volume scattering and positively affect backscatter intensity [27]. Existing studies on the effect of tundra vegetation on backscatter [23,32,56] do not address the effect of fresh vegetation on previously degraded tundra surfaces. The mixed signals of vegetated and eroding surfaces within the cliff AOIs could explain the higher standard deviations of backscatter in 2015.…”

Section: Backscatter Dynamics Of Tundra and Cliff Surfacesmentioning

confidence: 99%

Monitoring Inter- and Intra-Seasonal Dynamics of Rapidly Degrading Ice-Rich Permafrost Riverbanks in the Lena Delta with TerraSAR-X Time Series

et al. 2017

View full text Add to dashboard Cite

Arctic warming is leading to substantial changes to permafrost including rapid degradation of ice and ice-rich coasts and riverbanks. In this study, we present and evaluate a high spatiotemporal resolution three-year time series of X-Band microwave satellite data from the TerraSAR-X (TSX) satellite to quantify cliff-top erosion (CTE) of an ice-rich permafrost riverbank in the central Lena Delta. We apply a threshold on TSX backscatter images and automatically extract cliff-top lines to derive intra-and inter-annual CTE. In order to examine the drivers of erosion we statistically compare CTE with climatic baseline data using linear mixed models and analysis of variance (ANOVA). Our evaluation of TSX-derived CTE against annual optical-derived CTE and seasonal in situ measurements showed good agreement between all three datasets. We observed continuous erosion from June to September in 2014 and 2015 with no significant seasonality across the thawing season. We found the highest net annual cliff-top erosion of 6.9 m in 2014, in accordance with above-average mean temperatures and thawing degree days as well as low precipitation. We found high net annual erosion and erosion variability in 2015 associated with moderate mean temperatures but above average precipitation. According to linear mixed models, climate parameters alone could not explain intra-seasonal erosional patterns and additional factors such as ground ice content likely drive the observed erosion. Finally, mean backscatter intensity on the cliff surface decreased from −5.29 to −6.69 dB from 2013 to 2015, respectively, likely resulting from changes in surface geometry and properties that could be connected to partial slope stabilization. Overall, we conclude that X-Band backscatter time series can successfully be used to complement optical remote sensing and in situ monitoring of rapid tundra permafrost erosion at riverbanks and coasts by reliably providing information about intra-seasonal dynamics.

show abstract

Section: Backscatter Dynamics Of Tundra and Cliff Surfacesmentioning

confidence: 99%

Monitoring Inter- and Intra-Seasonal Dynamics of Rapidly Degrading Ice-Rich Permafrost Riverbanks in the Lena Delta with TerraSAR-X Time Series

et al. 2017

View full text Add to dashboard Cite

show abstract

“…The study area is a 60-km 2 region situated in the vicinity of the Inuit community of Umiujaq (56.55°N, 76.55°W) on the eastern shore of the Hudson Bay, Nunavik (Northern Quebec, QC, Canada; see Figure 1), it has been used in many studies and described in a prior paper by Duguay et al [26]. It is a discontinuous permafrost zone positioned at the northern tree line, forming a transition between the forest tundra to the south and the shrub tundra to the north.…”

Section: Study Areamentioning

confidence: 99%

“…Classes with shrub coverage tend to retain more snow, as demonstrated in [1,2,12], which causes ground temperatures to be warmer during the winter, enabling a better differentiation from classes with little or no shrub coverage. The volume scattering component from the vegetation is also affected by snow cover, as snow tends to attenuate the scattering from the vegetation due to the lower dielectric contrast between the shrub branches and the snow [26].…”

Section: Class Symbolmentioning

confidence: 99%

“…Previous studies have shown that SAR imagery can be a suitable tool to detect, quantify and map shrub vegetation, but mostly in arid or semi-arid environments [22][23][24][25]. More recently, it has been demonstrated that C-and X-band SAR backscattering is sensitive to shrub height in sub-Arctic environments [26]. In particular, it was shown that C-band SAR backscattering is most sensitive to shrub height when the stands are shorter than one meter and is most sensitive to changes in shrub coverage when it is below 20%.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Land Cover Classification in SubArctic Regions Using Fully Polarimetric RADARSAT-2 Data

et al. 2016

Self Cite

View full text Add to dashboard Cite

Abstract:The expansion of shrub vegetation in Arctic and sub-Arctic environments observed in the past decades can have significant effects on northern ecosystems. There is a need for efficient tools to monitor those changes, not only in terms of the spatial coverage of shrubs, but also their vertical growth. The objective of the current paper is to evaluate the performance of polarimetric C-band SAR datasets for land cover classification in sub-Arctic environments. A series of RADARSAT-2 quad-pol images were acquired between October 2011 and April 2012. The Support Vector Machine (SVM) classification scheme was used on three sets of features: the elements of the polarimetric coherency matrix [T], the parameters extracted from a polarimetric decomposition based on the eigenvalues and eigenvectors of [T] and the parameters extracted from a model-based decomposition. Using a single image, the results show that the best classification accuracies (≈ 75%) are obtained using the [T] matrix with the October images. When adding a second image to the feature set, either from two different dates or two incidence angles, the classification accuracy is improved and reaches 90.1% with two images from October 2011 and April 2012 at 27 • incidence. The results show that C-band polarimetric SAR imagery is an adequate tool to map shrub vegetation in sub-Arctic environments.

show abstract

“…In addition to bare ground and water, previous research has also demonstrated the sensitivity of TSX (VV/HH polarized) data to the presence of Arctic shrubs and vegetation communities in summer [83], as well as in winter under a dry snow cover [84]. Under both conditions, backscatter is expected to increase with higher shrub density because the fraction of volume scattering increases with taller vegetation.…”

Section: Technical Considerations For Using Tsx For Wet Snow Detectionmentioning

confidence: 99%

TerraSAR-X Time Series Fill a Gap in Spaceborne Snowmelt Monitoring of Small Arctic Catchments—A Case Study on Qikiqtaruk (Herschel Island), Canada

et al. 2018

View full text Add to dashboard Cite

Abstract:The timing of snowmelt is an important turning point in the seasonal cycle of small Arctic catchments. The TerraSAR-X (TSX) satellite mission is a synthetic aperture radar system (SAR) with high potential to measure the high spatiotemporal variability of snow cover extent (SCE) and fractional snow cover (FSC) on the small catchment scale. We investigate the performance of multi-polarized and multi-pass TSX X-Band SAR data in monitoring SCE and FSC in small Arctic tundra catchments of Qikiqtaruk (Herschel Island) off the Yukon Coast in the Western Canadian Arctic. We applied a threshold based segmentation on ratio images between TSX images with wet snow and a dry snow reference, and tested the performance of two different thresholds. We quantitatively compared TSX-and Landsat 8-derived SCE maps using confusion matrices and analyzed the spatiotemporal dynamics of snowmelt from 2015 to 2017 using TSX, Landsat 8 and in situ time lapse data. Our data showed that the quality of SCE maps from TSX X-Band data is strongly influenced by polarization and to a lesser degree by incidence angle. VH polarized TSX data performed best in deriving SCE when compared to Landsat 8. TSX derived SCE maps from VH polarization detected late lying snow patches that were not detected by Landsat 8. Results of a local assessment of TSX FSC against the in situ data showed that TSX FSC accurately captured the temporal dynamics of different snow melt regimes that were related to topographic characteristics of the studied catchments. Both in situ and TSX FSC showed a longer snowmelt period in a catchment with higher contributions of steep valleys and a shorter snowmelt period in a catchment with higher contributions of upland terrain. Landsat 8 had fundamental data gaps during the snowmelt period in all 3 years due to cloud cover. The results also revealed that by choosing a positive threshold of 1 dB, detection of ice layers due to diurnal temperature variations resulted in a more accurate estimation of snow cover than a negative threshold that detects wet snow alone. We find that TSX X-Band data in VH polarization performs at a comparable quality to Landsat 8 in deriving SCE maps when a positive threshold is used. We conclude that TSX data polarization can be used to accurately monitor snowmelt events at high temporal and spatial resolution, overcoming limitations of Landsat 8, which due to cloud related data gaps generally only indicated the onset and end of snowmelt.

show abstract

Potential of C and X Band SAR for Shrub Growth Monitoring in Sub-Arctic Environments

Cited by 42 publications

References 40 publications

Monitoring Inter- and Intra-Seasonal Dynamics of Rapidly Degrading Ice-Rich Permafrost Riverbanks in the Lena Delta with TerraSAR-X Time Series

Monitoring Inter- and Intra-Seasonal Dynamics of Rapidly Degrading Ice-Rich Permafrost Riverbanks in the Lena Delta with TerraSAR-X Time Series

Land Cover Classification in SubArctic Regions Using Fully Polarimetric RADARSAT-2 Data

TerraSAR-X Time Series Fill a Gap in Spaceborne Snowmelt Monitoring of Small Arctic Catchments—A Case Study on Qikiqtaruk (Herschel Island), Canada

Contact Info

Product

Resources

About