HR: 1340h
AN: H23D-1152    [Abstracts]
TI: Effect of Snow Cover on the Characterization of Seasonal Freeze-Thaw Processes From Spaceborne Radar
AU: * Podest, E
EM: erika.podest@jpl.nasa.gov
AF: Jet Propulsion Laboratory/Caltech, 4800 Oak Grove Dr. Box 300-233, Pasadena, CA 91109 United States
AU: McDonald, K C
EM: kyle.mcdonald@jpl.nasa.gov
AF: Jet Propulsion Laboratory/Caltech, 4800 Oak Grove Dr. Box 300-233, Pasadena, CA 91109 United States
AU: Kimball, J S
EM: johnk@ntsg.umt.edu
AF: University of Montana, Flathead Lake Biological Station 311 Biostation Ln, Polson, MT 59860 United States
AU: Hardy, J P
EM: janet.p.hardy@erdc.usace.army.mil
AF: ERDC Cold Regions Research and Engineering Laboratory, 72 Lyme Road, Hanover, NH 03755 United States
AB: In boreal forests, the seasonal transition between frozen and thawed conditions affects a number of terrestrial processes that cycle between winter dormancy and summer active states. Accurate characterization of these processes can improve regional assessment of seasonal carbon dynamics. Satellite microwave remote sensing is sensitive to landscape freeze/thaw state and has been used for regional assessment and monitoring of this important process at high latitudes and upper elevations. The presence and status of snow cover strongly influences accurate detection and monitoring of freeze/thaw status using microwave sensors. We investigate the effect of snow cover on characterization of landscape freeze-thaw dynamics with spaceborne radars. We examine time series spaceborne Synthetic Aperture Radar (SAR) imagery from ERS (C-band) and JERS (L-band), and scatterometer backscatter from QuikSCAT (Ku-Band) and utilize a radiative transfer backscatter model for interpretation of snow cover effects on the radar signatures. We focus on the interpretation of seasonal thawing relative to snowpack dynamics in a boreal environment. The study sites represent a selection of snow regimes over a range of climatic conditions, from relatively shallow boreal continental snowpacks to deep, wet maritime snowpacks. We employ SNTHERM, a one-dimensional mass and energy balance model, at a stand scale to calculate critical snow properties. SNTHERM is used to infer the snowpack conditions at selected sites and to drive the snow backscatter model. We compare the measured radar backscatter response at each study site to the snow backscatter model and SNTHERM results. We show the radar temporal response to the landscape thaw transition and assess the radar sensitivity to snowpack properties. Finally, we demonstrate how varying snow conditions, characteristic of a boreal landscape, affect freeze-thaw characterization at different wavelengths. This work was performed at the Jet Propulsion Laboratory, California Institute of Technology, at the University of Montana, Missoula, and at the U.S. Army Corps of Engineers Cold Regions Research and Engineering Lab under contract with the National Aeronautics and Space Administration.
DE: 1863 Snow and ice (1827)
SC: Hydrology [H]
MN: 2004 AGU Fall Meeting