1 / 26

Microwave Emissivity of a Sea Foam Layer for WindSat Algorithm

Explore surface emissivity challenges in modeling sea foam layer for WindSat retrieval with a physical model emphasizing foam emission components.

kroldan
Download Presentation

Microwave Emissivity of a Sea Foam Layer for WindSat Algorithm

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Microwave Emissivity of a Vertically Inhomogeneous Sea-Foam Layer:Application to the WindSat Retrieval Algorithm Magdalena D. Anguelova, Karen St. Germain, Craig Smith, Peter Gaiser, Richard Bevilacqua, Nai-Yu Wang, Michael Bettenhausen Remote Sensing Physics Branch Naval Research Laboratory 21 September, 2004

  2. WindSat forward model • Radiative transfer equation: • Semi-empirical surface model: e = er + Δe • 2-scale model for er; • WindSat data for Δe.

  3. Complete physical model • Surface emissivity: • Difficulties in modeling e: • Two-scale model limitations; • Limited knowledge for ef ; • Separate er and ef ; • High uncertainty for f ;

  4. Whitecaps on the surface Bubble plumes below the surface Sea foam

  5. Foam void fraction

  6. ε' ε" 6.8 GHz 18.7 GHz 37.0 GHz Foam dielectric constant

  7. air seawater Matching impedances

  8. air seawater air foam (98%) foam (10%) seawater Matching impedances

  9. F GHz λ0 cm λf cm fa= 98% λf cm fa= 10% 6.8 4.4 3.2 0.60 10.7 2.8 2.1 0.41 Tdown 18.7 1.6 1.31 0.28 23.8 1.3 1.1 0.26 37.0 0.8 0.72 0.20 Tsc Mechanisms of attenuation • Absorption: • 85%-90%; • Small in bubble walls; • Max at water boundary; • Scattering: • 10%-15%; • λ-dependent. Max bubble dia 2 cm Min bubble dia 0.02 cm

  10. + = + + + Foam-covered area TB • Reflection/scattering terms; • Emission terms. z = 0 z = -d TBf

  11. Droppleman, 1970 Rosenkranz and Staelin, 1972 Raizer and colleagues 1982, 1992 Chen et al., 2003 Model requirements • Vertically inhomogeneous layer; • Absorption and scattering; • Various contributions to foam emission.

  12. Foam emission

  13. Our choice • Macro characteristics (layer); • Vertically inhomogeneous (depth profile); • Flat specular boundaries; • Incoherent approach -- weak scattering; • Ignore scattering term; z = 0 Air, ε0=1 Foam, ε (z) z = -d Water, ε

  14. Void fraction profile

  15. Foam dielectric constant

  16. Foam attenuation coefficient

  17. Foam refraction

  18. Foam emission components + diffuse scattering term dz

  19. dz Foam emission components

  20. dz Foam emission components

  21. dz Foam emission components

  22. + = + + + Foam contributions d/0  0.02 d =0/50 320 m d/0= 0.25 d = 0/4 4 mm TBf0

  23. Reising et al., 2002 TBf over distribution of thickness

  24. Foam emission

  25. Foam emission

  26. Necessary experiments • Void fraction profile; • Values for boundary conditions; • Bubble size distribution; • Thickness distribution; • Azimuthal dependence.

More Related