The long-term objective of this project is to enable near-daily satellite monitoring of thickness and water content of the active layer throughout the circumpolar Arctic. The PIs propose to test two hypotheses within the framework of Arctic-CHAMP: 1) Assimilation of plot-scale 1.4 or 6.9 GHz brightness in SVAT/Radiobrightness models will yield reliable histories of thickness and moisture content of the permafrost active layer; and 2) Assimilation of satellite-scale 1.4 or 6.9 GHz brightness in a distributed hydrology model having embedded SVAT/Radiobrightness linkages will yield meaningful spatially aggregated active layer histories. This assertion is supported by REBEX-3 data, which show plotscale 19 GHz brightness data (~3 m) to be nearly identical to SSM/I satellite-scale 19 GHz brightness data (~50 km) - a 4 order of magnitude span in spatial resolution. Soil-Vegetation-Atmosphere Transfer (SVAT) models depict energy and moisture transport and storage processes in soil, vegetation, and snow. SVAT moisture profiles have been made accurate to meter depths through assimilation of the moisture content of the top 5 cm of soil inferred from 1.4 GHz brightness. Although similar tests have not been made with 6.9 GHz data, these data have significant sensitivity to soil moisture and are now available from the new AMSR satellite instrument. For the assimilation approach with either frequency to work in the Arctic requires that tundra SVAT models linking active layer moisture content to microwave brightness be developed and calibrated. A NASA Global Water and Energy Cycle (GWEC) Program grant is permitting the PIs to build upon the success of their prairie Land Surface Process/Radiobrightness (LSP/R) model to develop and calibrate a diagnostic LSP/R model for arctic tundra. The GWEC project includes a six-week, plot-scale calibration experiment near Toolik Lake in 2004. The PIs propose to (1) extend that calibration experiment to the entire summer season, (2) create a parameterized inversion model to assimilate 1.4 or 6.9 GHz brightness data from the calibration experiment to test hypothesis 1, (3) embed the tundra LSP/R model and the parameterized inversion model in an existing hydrology model of the upper Kuparuk River watershed, (4) acquire AMSR satellite 6.9 GHz brightness data and create a season-long "nature run" of 1.4 GHz brightness data for an area of the Watershed equal to a satellite footprint (~2,500 km2), and (5) assimilate the satellite and synthesized nature run data to test hypothesis 2. The research is interdisciplinary between the Department of Atmospheric, Oceanic, and Space Sciences and the Department of Electrical Engineering and Computer Science at the University of Michigan. It offers scientists and engineers across these disciplines unique collaborative opportunities to introduce new technologies to arctic environmental science.
