1. OC3522Summer 2001 OC3522 - Remote Sensing of the Atmosphere and Ocean - Summer 2001 Ocean Color

2. L t ( ) =  L w ( ) + L G ( ) + L 0 ( ) ) + L A ( )+ L r ( )

3. L t = L 0  0 + L rayleigh +L aerosal L 0  0 = radiance leaving surface = L reflectance & L water

4. Surface Reflectance Specular (mirror-like) ii rr Diffuse ii L G ( ) = glint radiance L W ( ) = water-leaving radiance

5. Sunglint Examples ftp://daac.gsfc.nasa.gov/data/czcs/oss_hires/97.tiff

6. L A ( ) = scattering due to aerosols (Mie) + molecular Raleigh scattering At a given wavelength; e.g.     70nm, L w = 0 Then L t ( ) = L r ( ) + L a ( ) ; measure L t ( ) ; estimate L a ( ); left with L r ( )

7. Bio Optical properties Suspended and dissolved substance Dominant compounds Chlorophyll dissolved organic compounds decayed organic matter “yellow substance” Maul, 1985

8. 123 4 5678 A ratio of the reflectance in one band to that in another can be used to determine chlorophyll concentrations Blue -443nm Yellow -550nm point near 500nm

9. Water Types Case I water Satellite Oceanography, Robinson (1983)

10. Case II waters: Suspended sediments

11. Case II waters: Gelbstoff (yellow substance)

12.  (  L w ( ) http://ltpwww.gsfc.nasa.gov/MODIS/MODIS.html 123 4 5678 SeaWiFS Channels increased concentration decreased concentration Compute the chlorophyll in the water

13. 12345678  (  L w ( ): CASE I waters The bio-optical algoritms for L w ( ): in water or upwelled radiance L w ( )  backscatter coeff./ absorbtion coeff. http://daac.gsfc.nasa.gov/WORKINPROGRESS/OCDST/ocdst_history_and_other_background_info.html blue green red

15. http://ltpwww.gsfc.nasa.gov/MODIS/MODIS.html 123 4 5678 SeaWiFS Channels increased concentration decreased concentration

16. Case 2-Glebstoff Case 1

17. Are the differences detectable?

18. Again for the general solution… To derive ocean properties, we want the path radiance to have a small and removable contribution: Three sources: scatter by clouds (non-removable) scatter by molecules (calculable as Rayleigh scatter) scatter by aerosol particles (implied from red/NIR channels) Then the surface radiance, L 0 ( ), can be derived from measurements of L t ( ) L 0 ( ) = L G ( ) + L W ( ) so if sunglint can be avoided by geometry, L 0 ( ) = L W ( ) (containing information about ocean constituents)

19. Previous Ocean Color instruments: Coastal Zone Color Scanner (CZCS) on Nimbus-7 Ocean Color and Temperature Scanner (OCTS) on ADEOS 412 nm 443 490 520 565 670 765 865 Channels 443 nm 520 550 670 750 Channels

20. SeaWiFS on SeaStar (Sea-viewing Wide Field-of-view Sensor)

21. http://svs.gsfc.nasa.gov/imagewall/SeaWiFS/useast_truecolor.html SeaWiFS channels: Band Center Wavelength (nm) Bandwidth Band Center Wavelength (nm) Bandwidth 1 412 20 2 443 20 3 490 20 4 510 20 5 555 20 6 670 20 7 765 40 8 865 40 12345678

22. BLUEGREEN

23. Shelf waters stirred by Hurricane Floyd Sept. 1999 July 27, 2001 Seawifs

24. 0.01 50

25. Jan 1986 June 1986

26. Feb 1983 Apr 1986