An Earth System Data Record for Land Surface Freeze/Thaw State: Quantifying Terrestrial Water Mobility Constraints to Global Ecosystem Processes
John
S
Kimball, Flathead Lake Biological Station and Numerical Terradynamic Simulation Group, University of Montana, Missoula MT., johnk@ntsg.umt.edu
(Presenting)
Kyle
C
McDonald, Jet Propulsion Laboratory, California Institute of Technology, Pasadena CA., kyle.mcdonald@jpl.nasa.gov
The landscape transition between seasonally frozen and non-frozen conditions occurs each year over more than 50 million km2 of the global biosphere, affecting surface hydrology and ecological trace gas dynamics profoundly. Satellite microwave remote sensing can detect large changes in landscape dielectric properties between frozen and non-frozen conditions. We are constructing an Earth System Data Record (ESDR) quantifying freeze/thaw (F/T) dynamics for the global vegetated land surface. The F/T ESDR (F/T-ESDR) involves multi-frequency satellite passive/active microwave remote sensing time series spanning multiple missions and sensors, including SMMR, SSM/I, AMSR-E, and SeaWinds. These records provide a contiguous global time series extending from 1979 onward with some overlap between missions. We employ a temporal change detection analysis of daily backscatter and brightness temperature time series to map F/T changes associated with temporal shifts in landscape dielectric properties between predominantly frozen and non-frozen conditions. We employ empirical methods and radar backscatter and microwave emissions models for merging overlapping sensor time series into well calibrated F/T time series. The F/T state variable provides a surrogate measure of water mobility in the landscape useful for analyzing cold temperature constraints for a range of biological and hydrologic processes, including photosynthesis and vegetation growing seasons, snowmelt and soil thaw, and recent global warming related impacts on these processes. The F/T-ESDR is being used to refine sensor configuration and accuracy requirements for future F/T measurements from the NASA Soil Moisture Active-Passive (SMAP) mission. Initial F/T-ESDR results are available online (http://ntsg.umt.edu) while further processing will continue through 2012.
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