Airborne SAR and passive microwave measurements over snow covered tundra for CoReH20 retrieval validation and land surface model testing
Principal Investigator: Derksen, Chris (4)
Licence Number: 15237
Organization: Environment Canada
Licenced Year(s): 2013 2012
Issued: May 01, 2013

Objective(s): To retrieve snow water equivalent (SWE) over land at a high spatial resolution (200-500 metres) from X- and Ku-band Synthetic Aperture Radar measurements. This would make available high resolution, satellite derived SWE, for monitoring and modeling applications. The objective of this project is to utilize a sub-Arctic open tundra watershed (Trail Valley Creek north of Inuvik, Northwest Territories, Canada) as a test bed for: (1) the CoReH20 satellite SWE retrieval approach. Because of a lack of standing vegetation, relatively homogeneous background soil moisture and temperature, and spatially variable SWE (due to wind redistribution) this is an ideal environment for the evaluation of SWE retrieval sensitivity, and (2) the potential use of CoReH20 SWE retrievals as observational inputs to various environmental prediction models, including land surface data assimilation systems and distributed hydrological models used at Environment Canada.

Project Description: The proposed European Space Agency Earth Explorer 7 CoReH20 satellite mission has the primary objective of retrieving snow water equivalent (SWE) over land at a high spatial resolution (200-500 metres) from X- and Ku-band Synthetic Aperture Radar measurements. This would make available high resolution, satellite derived SWE, for monitoring and modeling applications. To-date, airborne measurements to test the CoReH20 satellite mission concept have been acquired over mixed forest terrain in Finland, where the vegetation canopy and complex dielectric background from wetlands and bogs make for a challenging retrieval environment.

The objective of this project is to utilize a sub-Arctic open tundra watershed (Trail Valley Creek north of Inuvik, Northwest Territories, Canada) as a test bed for: (1) the CoReH20 satellite SWE retrieval approach. Because of a lack of standing vegetation, relatively homogeneous background soil moisture and temperature, and spatially variable SWE (due to wind redistribution) this is an ideal environment for the evaluation of SWE retrieval sensitivity, and (2) the potential use of CoReH20 SWE retrievals as observational inputs to various environmental prediction models, including land surface data assimilation systems and distributed hydrological models used at Environment Canada.

In order to evaluate the CoReH20 satellite SWE retrieval capability, the research team proposes airborne measurements with the European Space Agency SnowSAR instrument, (a replica of the same instruments that would be placed onboard the CoReH20 satellite platform), over the Trail Valley Creek watershed near Inuvik, Northwest Territories. A previous airborne snow remote sensing campaign was conducted in this region by Environment Canada in 2008. Snow measurements and distributed hydrological modeling activities have been conducted by Environment Canada in Trail Valley Creek since 1995. The current measurement plan includes the acquisition of near-coincident airborne SAR and passive microwave measurements over open canopy forest, tundra, and lake ice in the Trail Valley Creek watershed. Thick permafrost conditions in the region (with a thin summer active layer) increase the likelihood that low-snow, frozen ground measurements can be acquired in December before substantial snow accumulation, while flights in March and April would ensure surveying of close to maximum seasonal snow accumulation. In situ snow measurements will include bulk snow properties (depth, density, SWE) along flight lines. A snow survey sampling strategy will be devised to determine airborne/satellite SWE retrieval sensitivity to observed local scale variability in snow distribution induced by topographic and vegetation influences. The survey design will also address the fundamental issue of scaling these high resolution measurements to match the scale proposed by future satellite missions. A seasonal sampling strategy (December-April) is required to address SWE retrieval sensitivity to within-season changes in snow depth and vertical snowpack complexity (snow grain growth, ice crusts).

Results of this study will be published in academic journals once the analysis of the data is complete. In-addition, the research team is willing to provide a public talk to community members to provide more background information on the type of work that they are doing, and to discuss the research with interested parties.

The fieldwork for this study will be conducted from April 25, 2013 to December 31, 2013.