SnowSAR in Canada: An evaluation of basin scale dual-frequency (17.2 and 9.6 GHz) snow property retrieval in a tundra environment Joshua King and Chris Derksen Climate Research Division Environment Canada Toronto, Ontario, Canada Thanks to: Nick Rutter, Tom Watts and all participants in the field campaign

Motivation Radar as an emerging technology for observation of snow properties ESA Earth Explorer CoReH 2 O Dual frequency 17.2 and 9.6 GHz (Ku- and X-band) synthetic aperture radar (SAR) Few studies have investigated seasonal/spatial Ku- and X-band radar response and no previous study in a tundra environments Ku VV VH

Research Gaps 1.Soil/Vegetation properties Uncertainties related to variation in soil and vegetation dielectrics 2.Snow grain properties Unbiased measurements may allow the role of large depth hoar to be evaluated 3.Scaling of observations Are small scale variations in snow and soil properties influential at the airborne and/or satellite level?

SnowSAR in Canada Airborne radar operating at the proposed CoReH 2 O frequencies 17.2 and 9.6 GHz Dual-polarization (VV, VH) 2 x 2 m spatial resolution Three observation campaigns in Trail Valley Creek near Inuvik, NWT (December 2012, March 2013, April 2013) Trench stratigraphy experiments Improved snow grain characterization (IRIS) Seasonal soil permittivity in multiple locations

Study area and plan

Flight data summary December - 0/27 March – 24/27 April - 23/27 Incidence angles between 38 and 55 degrees Local incidence angles between 26 and 62 degrees Swath generally < 400 m All 4 channels (Ku and X VV, VH) available with all completed flight lines

Snow Measurement Campaign Snow Pit (< 1 m) Snow Trench (5 to 50 m) Snow Transect (> 100 m) Lidar (Basin scale)

Sic Sic Creek Basin

Sic Sic Creek - Snow Pit Locations Upland Tundra River Valley Forest Transition Pit Locations

December March April March Sic Sic Creek - Seasonal Upland Plateau Valley Forest transition Pit Locations

Sic Sic Creek - Backscatter Upland Plateau Valley Forest transition April 2013, 50 m, deg elevation

MEMLS Workflow – Pit MEMLS Active Surface Roughness Snow Pits SSA to P c From IRIS 2-Layer Snowpack Snow Input 1 Wegmüller & Mätzler (1999) Mironov (2010) MET Tower Data Observed Data Derived Data Simulated Data M = 0.05 Q = 0.1 Sccho = 13

Sic Sic Creek - MEMLS Active 10 m average of observed radar backscatter Small range of depth suggest grains may be an important in sic sic creek Can we compare single pits against radar pixels?

Sic Sic Valley - 5 m Trench IR photography completed in 5 to 50 m trench excavations by Watts & Rutter Stratigraphy extracted from stitched IR imagery to create 2D map

Sic Sic Valley - 5 m Trench Topography produces a range of depth over short distances Also tends to drive DH fraction Distribution of grain properties built from snow pits within +-3 days Due to the nature of tundra snow, the slab distribution includes solid facets

MEMLS Workflow – Distribution MEMLS Active Trench Excavation Surface Roughness Stratigraphy Distribution Snow Pits Grain Distribution 2-Layer Snowpack Snow Input 1 Snow Input 2 Snow Input n Wegmüller & Mätzler (1999 Mironov (2010) MET Tower Data Field Data Derived Data Simulated Data

Valley Trench – MEMLS Active

Summary/Moving forward Relating backscatter to physical snow properties is a complex process –Improved understanding of horizontal variation in grain properties and stratigraphy is needed Model advancement and inversion possible but requires community effort to assist in validation –Physically based justification for tuning possible with known distributions Additional uncertainties including soil contribution must be resolved in the near future

Snow texture

Vegetation Backscatter appears influenced by local vegetation Methods needed to decompose contributions from vegetation and snow to develop retrieval

Upland Tundra – Soil Permittivity

Snow Measurement Campaign Snow Pit (< 1 m) Snow Trench (5 to 50 m) Manual Stratigraphy Density (100 cc cutter) Temperature Profile (4 cm) IRIS SSA (5 cm) IR Stratigraphy Multiple snow pits IRIS SSA (5 cm)

Snow pits in local context