New Projects: Collaborators Sought

1. New Projects: Collaborators Sought NSF OPP Instrumentation Project: STAR-Light – a 1.4 GHz aperture synthesis radiometer for use on light aircraft in arctic land-surface hydrology PI – England NASA GEWEC Project: The subsurface geothermal climate signal in the context of LSP/Radiobrightness model-based estimates of land-atmosphere energy and moisture fluxes for regions of the circumpolar Arctic Co-PI’s – England and Pollack

2. Background REBEX-3 Toolik Lake Alaska 1994-1995 1) Climate models predict early & significant warming in the Arctic • Transition of Arctic tundra from carbon sink to carbon source • 2) Geothermal climate signal is used to infer climate trends • Unclear how surface processes influence the geothermal gradient • 3) Desire to use satellite microwave radiometry to monitor annual duration and water content of active layer

3. Atmospheric Model Satellite L-band Radiometer Tb(observed) Weather & downwelling irradiance Land Surface Process Model Assimilate Tb(observed) - Tb(model) Temperature & Moisture Profiles Tb (model) Radiobrightness Model Strategy for Monitoring Arctic Tundra

4. 1.4 GHz Radiometer on Light Aircraft Would Facilitate Remote Sensing Hydrology in Arctic • Calibration of Arctic LSP/R model requires data from thawing in spring to freezing in fall • Arctic is inaccessible to grounds surveys in summer • NASA radiometers fly on 4-engine, turboprop aircraft like the C-130 and P-3 • Operations costs of these aircraft are prohibitive • Operations costs of STAR-Light will be < 5% those of NASA systems enabling season-long field campaigns

5. STAR-Light Objective: • Build a reliable L-band imaging radiometer for use on light aircraft in Arctic land-surface hydrology Strategy: • STAR technology • Direct Sampling Digital Receivers (DSDR) • Band definition filters in digital domain

6. 0.68 l 0.44 m Flight Direction STAR-Light element configuration Requirements for STAR-Light • 1.4 GHz, 10-element, circularly polarized, aperture synthesis radiometer • Angular resolution: < 22o with > 90% beam efficiency • NET < 0.1 K desired, < 0.5 K required • Calibration: < 2 K desired, < 3 K required • Linear dynamic range 5 K < Tb < 300 K • Ambient operating range -30o C < To < +30o • Across-track scan to ±35o • Along-track scan + 20o / -50o • Operation on a Super Cub-class aircraft for extended periods in the Arctic

7. Future Satellite System Sketch of the ESA Soil Moisture Ocean Salinity (SMOS) satellite

8. Objectives of our GEWEC Project • Develop a tundra LSP/R model that will credibly generate the downward propagating temperature signal used to infer past climate • Quantify constraints placed upon the land-atmosphere energy and moisture fluxes by the geothermal climate signal • Quantify expected errors in estimated land-atmosphere energy and moisture fluxes obtained from the tundra LSP/R model and assimilated AMSR or SMOS data

9. Principal Tasks of our GEWEC Project • Develop a physically plausible LSP/R model for tussock tundra • Calibrate the model with data from a REBEX-style field experiment near Toolik Lake, Alaska, during summer of 2003 • Establish the open-loop sensitivity of model-generated geothermal signals to plausible ranges of land-atmosphere energy and moisture fluxes • Compare modeled geothermal climate signals with borehole temperature data in permafrost from the Alaskan North Slope