Evaluating the Sensitivity of C-Band RADARSAT-2 SAR Data to Active Layer Soil Moisture over Arctic Tundra in Trail Valley Creek, NT.
Evaluating the Sensitivity of C-Band RADARSAT-2 SAR Data to Active Layer Soil Moisture over Arctic Tundra in Trail Valley Creek, NT.
Previously Published Material: Preliminary findings of this research were repoted as part of a poster at the Arctic Change 2014 conference in Ottawa (December 8-12, 2014). Only very preliminary analysis was shown and further investigation has revealed new findings, presented here.
Abstract ID#: 33702
English Abstract:
Monitoring soil moisture is very important for understanding hydrological, climatic, and biogeochemical phenomena. However, the measurement of soil moisture over the arctic tundra is challenging due to its inaccessibility and it is important that new techniques are developed. Earth observation satellites utilizing active C-band microwaves have been found to be sensitive to surface soil moisture (top 5 cm) in mineral soils; however less is understood about their sensitivity to organic soils underlain by continual permafrost . The objective of this research is to assess the sensitivity of RADARSAT-2 to surface soil moisture in the arctic tundra. For this research, 5 plots (42 m x 42 m) were established at Trail Valley Creek, NT, where soil moisture measurements in 5 cm and 20 cm depths were sampled every 7 m, coincident to two RADARSAT-2 overpasses (θ = 24°) in July of 2014. Linear backscatter values (σ°HH, σ°HV, σ°VV) extracted from the SAR images were compared to field measured soil moisture at each depth using linear regression. On July 24, the cross-polarization ratio (σ°HV/HH) was found to be most significantly correlated to field measured soil moisture at both depths, with the 20 cm depth sampled soil moisture demonstrating stronger correlation (r2=0.79) to the backscatter response than measurements at the 5 cm sampling depth (r2=0.67). After significant rainfall on July 27th, the 5 cm sampling depth was found to be more correlated to the backscatter variables than the 20 cm sampling depth. These preliminary results provide new insight into the interaction of SAR microwaves with peat soils. Additionally, this demonstrates promise for operational measurements of active layer soil moisture from C-band SAR sensors, such as RADARSAT-2 and the planned RADARSAT-Constellation mission. These measurements will be valuable for understanding and modelling environmental processes, including permafrost thaw patterns and vegetation shifts, which is of utmost importance given the strong influence of climate change in the Arctic.