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Satellite Microwave Radiometry: Current and Future Products

Satellite Microwave Radiometry: Current and Future Products. Rogre De Roo and Tony England Atmospheric, Oceanic, and Space Sciences. Outline. Principles of Microwave Radiometry Observables History of spaceborne missions Future missions and opportunities.

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Satellite Microwave Radiometry: Current and Future Products

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  1. Satellite Microwave Radiometry:Current and Future Products Rogre De Roo and Tony England Atmospheric, Oceanic, and Space Sciences

  2. Outline • Principles of Microwave Radiometry • Observables • History of spaceborne missions • Future missions and opportunities

  3. What’s so great about Microwave Remote Sensing? Tx Rx Rx • Long wavelengths (3mm to 30cm) don’t scatter off of objects the size of • cloud droplets -- microwaves see through clouds • 2. Source of power is independent of the sun -- microwaves see at night and day Radar Radiometry • Very high spatial resolution • Power hungry: expensive • Sensitive to geometry of water • Poor spatial resolution • Low power requirements • Insensitive to geometry of water

  4. Microwave Radiometry & Planck Radiation 8000K white hot the Sun 3000K red hot 300K room temp 30K 3K outer space 1 GHz 0.3 m 1 THz 0.3 mm 1 PHz 0.3 um frequency wavelength

  5. Microwave Characteristics of the Atmosphere from LeVine, Wilheit, Murphy and Swift, 1989

  6. Microwave Brightness and Moisture Space 2.7K Space 2.7K Sensor Sensor Dry Soil ~300K Wet Soil ~300K • Water molecules have large electric dipole, unlike rest of nature • An interface w/ high contrast of index of refraction leads to reflection • Dry soils appear warm, while wet soils appear cold, at the same temp. Liquid water molecules will orient itself with passing electromagnetic waves,slowing the wave down The molecule can keep up with the wave until ~9 GHz (index of refraction: n = 9 at 1 GHz, but n = 2 at 100 GHz) H - O + H

  7. Freeze/ Thaw Example:Liquid watern=9Frozen water (ice) n=1.77

  8. Strategy for Estimating Stored Water Atmospheric Model Satellite L-band Radiometer Tb(observed) Weather & downwelling radiance SVAT Model Assimilate Tb(observed) - Tb(model) Temperature & Moisture Profiles Tb (model) Radiobrightness Model Microwave Geophysics Group calibrating models in AK, 1995

  9. Products by frequency Also: -Sea surface salinity at 1.4GHz -Vegetation moisture content at 1.4 and 6 GHz -Vegetation temperature at 18 – 90 GHz from LeVine, Wilheit, Murphy and Swift, 1989

  10. Future Systems and Opportunities: 1.4GHz (21cm) • SMOS (by ESA) in 2007: a very ambitious electronically steered array to collect soil moisture at 50 km and sea surface salinity at 300 km • Aquarius (by NASA) in 2010: relatively traditional design optimized for sea surface salinity observations. • HYDROS (by NASA) in 2012: relatively traditional design optimized for soil moisture measurements. • Soil moisture measurements have obvious hydrological value to GLACEO • Sea surface salinity…

  11. Sea Surface Salinity ??? • Great Lakes are a natural calibration target for a SSS mission: • Body of water with known salinity (none!) • Large extent for low spatial resolution observations • Conveniently located close to many scientists • However, spatial resolution for SSS is so poor, even Lake Superior may not be big enough. • Accurate meteorological and ecological data on the lakes and nearby lands will add utility to use of the lakes as calibration / validation target.

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