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Sea ice remote sensing from space

Sea ice remote sensing from space. Remote Sensing I Lecture 10 Summer 2006. Sea ice remote sensing from space. Optical (e.g. MODIS) High resolution (about 100 meters) Can‘t „see“ through clouds; difficult to distinguish clouds and sea ice Passive Microwave

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Sea ice remote sensing from space

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  1. Sea ice remote sensing from space Remote Sensing I Lecture 10 Summer 2006

  2. Sea ice remote sensing from space • Optical (e.g. MODIS) • High resolution (about 100 meters) • Can‘t „see“ through clouds; difficult to distinguish clouds and sea ice • Passive Microwave • Can differentiate between open water, first year and multiyear ice • Can „see“ through clouds • Low spatial resolution (several km) • Radar • Can look through clouds • High spatial resolution (< 1km) • Images difficult to interprete

  3. MODIS - Antarctica 21 March 2005

  4. Radar Image ENVISAT ASAR 15 April 2005

  5. Sea ice concentration fromAMSR-E 89 GHz 09 July 2006 www.seaice.de courtesy of Lars Kaleschke

  6. Sea ice concentration fromAMSR-E 89 GHz 23 April 2006 courtesy of Lars Kaleschke

  7. 1. RADAR

  8. Opening angle β h Xa S Xr Real Aperture Radar Viewing angle θ

  9. Antenna beamwidth The opening angle β (beamwidth) of an antenna with aperture D at a wavelength of λ is given by: The azimuth resolution for a real aperture radar is then

  10. Azimuth resolution fro real aperture radar Example: h=800km, λ=23cm, D=12m then Xa=16km This is a coarse resolution!

  11. Synthetic aperture radar: Schematic L Radar flight direction Ground L

  12. Synthetic aperture radar Ground „footprint“ L given by: Individual measurements can be combined, corresponding to a Measurement with a virtual or synthetic aperture of size L. The resolution for such a synthetica aperture radar (SAR) is thengiven by:

  13. 2. Passive Microwave Sensors

  14. Passive microwave remote sensing

  15. Emissivity of Sea Ice vs. Frequency Summer First year Ice Multiyear Ice Emissivity Water Frequency [GHz]

  16. Polarization Ratio (PR) and Spectral Gradient (GR) Clouds

  17. Sea ice concentration The sea ice surface concentration C can then be calculated from the contributions of the three base points for open water, first year ice, and multi year ice. The sum of the three concentrations must sum to unit:

  18. MODIS 645, 555, 469 nm AMSR-E 89 GHz courtesy of Lars Kaleschke

  19. Optical tick clouds are still transparent at 89 GHz courtesy of Lars Kaleschke

  20. courtesy of Lars Kaleschke

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