High resolution ground-based snow measurements during the NASA CLPX-II campaign, North Slope, Alaska

Transcription

1 High resolution ground-based snow measurements during the NASA CLPX-II campaign, North Slope, Alaska H.P. Marshall1, N. Rutter2, K. Tape3, M. Sturm4, R. Essery5 1 Boise State University, Department of Geosciences 2 University of Sheffield, Department of Geography 3 University of Alaska-Fairbanks, Department of Biology and Wildlife 4 U.S. Army Cold Regions Research and Engineering Laboratory 5 University of Edinburgh, School of Geosciences Fall 2008 AGU, Remote Sensing of the Cryosphere II, C12B-05

2 Acknowledgements x and Water Cycle Sponsored (NEWS) NASA Energy Research / Terrestrial Hydrology Program z Don Cline (NOAA), Kelly Elder (USFS) NERC Post-doctoral Fellowship (N. Rutter) Jon Holmgren, Jerry Johnson (CRREL) Toolik Research Station Crew

3 Cold Land Processes Experiment II Science Objectives Support U.S. and international science objectives in: Hydrology, Global Water Cycle, Cryosphere, and Climate International Polar Year Support snow remote sensing missions in U.S. and Europe NASA Snow and Cold Land Processes Mission (SCLP) ESA Cold Region High-resolution Hydrologic Observatory (CoRe-H2O) Test and develop high-frequency radar (Ku-, X-band) remote sensing techniques for measuring snow water equivalent (SWE) Quantify the radar sensitivity to key snowpack properties Don Cline, Kelly Elder, Test the theoretical basis for the radar measurements Simon Yueh Develop improved measurement capabilities

4 Alaska USA February N, above tree line

5 Kuparuk River study area Study Area #2 Dalton Highway Trans-Alaska Pipeline Toolik Field Station Sagavanirktok River Imnaviat Creek Snow Course (UAF) (courtesy of Don Cline, NOAA) N Landsat ETM+ July 1999 Bands 5,3,2 Projection: UTM Zone 6N Datum: WGS84

6 From point to footprint scales Snowpit Transect Region Cm-meter Meter-km 100 m- 10 km

7 Large variability at 1-10m scale Vegetation Small scale topography Wind Shallow snowpack Snow Depth

8 Trench Scale Sub mm- 10 m Snowpit Cm- m Transect Meter-km [e.g. Sturm and Benson, 2004]

9 A Natural Laboratory Representative of depth, SWE, stratigraphy variability within study site Allowed characterization of snowpack at very high resolution, with a wide range of tools, in wide range of conditions All tools used sensitive to snow structure, which has large effect on airborne/spaceborne passive/active radar

10 Kuparuk River study area Study Area #2 Dalton Highway Trans-Alaska Pipeline Sagavanirktok River Toolik Field Station Imnaviat Creek Snow Course (UAF) (courtesy of Don Cline, NOAA) N Landsat ETM+ July 1999 Bands 5,3,2 Projection: UTM Zone 6N Datum: WGS84

11 Stratigraphy on flat surface

12 Stratigraphy on flat surface

13 Stratigraphy on flat surface

14 Stratigraphy on flat surface

15 Stratigraphy on flat surface

16 Detailed manual stratigraphy 51 layer profiles x 20cm

17 Detailed density measurements 6 density profiles Layer grain size/ grain type x 2m V 100cm3

18 In-situ dielectric measurements Snowfork x 50 cm z 5 cm

19 In-situ dielectric measurements Snowfork x 50 cm z 5 cm

20 Microstructure / harness profiles SnowMicroPenetrometer x 20 cm z mm [Schneebeli & Johnson, 1998; Fall 2008 AGU, Remote Sensing of the Cryosphere II, C12B-05 Johnson & Schneebeli, 1999]

21 Microstructure / harness profiles SnowMicroPenetrometer x 20 cm z mm Lutz et al, C21C-0579, Tues. 8am

22 Near-InfraRed (NIR) photography x 0.2 cm z 0.2 cm Sturm et al, C34A-05, Wed 5:00 Schneebeli, C34A-06, Wed 5:15 Rutter et al, C34A-07, Wed 5:30 Barnola et al, C21C-0560, Tues. 8am [Matzl & Schneebeli, J. Glac., 2007]

23 Stratigraphy / NIR repeated in 3 trenches

24 Broadband Microwave radar x 0.02 cm z 1 cm A 50 cm x 50 cm 2-10 GHz 8-18 GHz high gain GHz dual pol. 0, 35 degrees incidence [e.g. Marshall & Koh, 2008]

25 Broadband Microwave radar Clear surface, ice returns accurate SWE estimates Layer roughness at scale less than footprint causes difficulty in radar stratigraphy interpretation

26 Broadband Microwave radar Clear surface, ice returns accurate SWE estimates Layer roughness at scale less than footprint causes difficulty in radar stratigraphy interpretation

27 Broadband Microwave radar

28 Stratigraphy on rough surface

29 Stratigraphy on rough surface

30 Stratigraphy on rough surface

31 Stratigraphy on rough surface

32 Stratigraphy on rough surface

33 Same layers indentified, km s apart

34 Rough layer surfaces at scale < footprint cause variable scattering

35 Radar backscatter at 35 degrees Significant scattering from rough layer surfaces

36 Conclusions Database of radar backscatter at wide range of parameters (2-18 GHz, dual pol, 0,35 degree collected coincident with CLPX II incidence) z x Measurements cover range of snowpack properties within Kuparuk (0-28 cm SWE) Detailed ground-truth measurements with wide range of high-res. instruments provide accurate characterization of snowpack conditions Provides test-bed for radiative transfer models In shallow snowpacks with large surface roughness, layer roughness can causes significant contribution to total measured backscatter at Ku-band frequencies Measurements at trench scale will be used to interpret ground-based radar profiles at km scale, and compared with airborne radar

37 Conclusions Database of radar backscatter at wide range of parameters (2-18 GHz, dual pol, 0,35 degree collected coincident with CLPX II incidence) z x Measurements cover range of snowpack properties within Kuparuk (0-28 cm SWE) Detailed ground-truth measurements with wide range of high-res. instruments provide accurate characterization of snowpack conditions Provides test-bed for radiative transfer models In shallow snowpacks with large surface roughness, layer roughness can causes significant contribution to total measured backscatter at Ku-band frequencies Measurements at trench scale will be used to interpret ground-based radar profiles at km scale, and compared with airborne radar

38 Conclusions Database of radar backscatter at wide range of parameters (2-18 GHz, dual pol, 0,35 degree collected coincident with CLPX II incidence) z x Measurements cover range of snowpack properties within Kuparuk (0-28 cm SWE) Detailed ground-truth measurements with wide range of high-res. instruments provide accurate characterization of snowpack conditions, Provides test-bed for radiative transfer models In shallow snowpacks with large surface roughness, layer roughness can causes significant contribution to total measured backscatter at Ku-band frequencies Measurements at trench scale will be used to interpret ground-based radar profiles at km scale, and compared with airborne radar

39 Conclusions Database of radar backscatter at wide range of parameters (2-18 GHz, dual pol, 0,35 degree collected coincident with CLPX II incidence) z x Measurements cover range of snowpack properties within Kuparuk (0-28 cm SWE) Detailed ground-truth measurements with wide range of high-res. instruments provide accurate characterization of snowpack conditions Provides test-bed for radiative transfer models In shallow snowpacks with large surface roughness, layer roughness can causes significant contribution to total measured backscatter at Ku-band frequencies Measurements at trench scale will be used to interpret ground-based radar profiles at km scale, and compared with airborne radar

40 Conclusions Database of radar backscatter at wide range of parameters (2-18 GHz, dual pol, 0,35 degree collected coincident with CLPX II incidence) z x Measurements cover range of snowpack properties within Kuparuk (0-28 cm SWE) Detailed ground-truth measurements with wide range of high-res. instruments provide accurate characterization of snowpack conditions Provides test-bed for radiative transfer models In shallow snowpacks with large surface roughness, layer roughness can causes significant contribution to total measured backscatter at Ku-band frequencies Measurements at trench scale will be used to interpret ground-based radar profiles at km scale, and compared with airborne radar