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Further Testing/Validation of the Satellite f/Q correction

Further Testing/Validation of the Satellite f/Q correction. Kenneth J. Voss, Nordine Souaidia, and Albert Chapin Department of Physics, Univ. of Miami Andre Morel and David Antoine Laboratoire d’Oceanographie de Villefranche Dennis Clark and Mike Ondrusek NOAA/NESDIS.

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Further Testing/Validation of the Satellite f/Q correction

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  1. Further Testing/Validation of the Satellite f/Q correction Kenneth J. Voss, Nordine Souaidia, and Albert Chapin Department of Physics, Univ. of Miami Andre Morel and David Antoine Laboratoire d’Oceanographie de Villefranche Dennis Clark and Mike Ondrusek NOAA/NESDIS Thank NASA for their support (under our MODIS validation work)

  2. Test of Q(o, , ) portion of Morel, Antoine, Gentili (2002)f/Q algorithm • Tests Q through the measurement of the upwelling radiance distribution, as: Q (o, , ) = Eu/L(o, , ) • A single measurement of the upwelling spectral radiance distribution gives Eu [through integration of Lu (o, , ) ] and L (o, , ), with the same instrument, so is an accurate method to get Q (o, , ). Note that f is not available, as it requires simultaneous measurement of Ed, a and bb.

  3. Previous experimental tests • Morel, Voss, and Gentili, 1995 (JGR) used the first generation electro-optic RADS system. One Chl value (0.3 mg/m3) and o from 30-80o. • Voss and Morel, 2005 (L&O) used the next generation RADS-II. Chl from 0.2 to 10 mg/m3, but o only from 30-40o deg. • Both from cruises off of San Diego and into Gulf of California, rather restricted geographically.

  4. New data set uses NuRADS Smaller system Only upwelling 6 wavelengths 2 minutes per spectral set Much better optical characteristics

  5. Morel, Antoine and Gentili (2002) model features • Index is Chl, o, v, and  • Important that Chl is just a convenient index into the tables…could do something else, but this works. • Includes Raman scattering (inelastic process). • Radiance distribution depends critically on the phase function. • Includes a phase function which varies with Chl, not just a single particle phase function to match observed bb variation with Chl. • Calculation uses spheroids, and not spheres (which can be anomalous in the backscattering direction.

  6. Data reduction • Process radiance distribution images according to Voss and Zibordi (1989). • Immersion test critical in underwater measurement, with curved windows not straight forward. • Additional steps to locate geometry required.

  7. Example image and reduced product AOPEX, 8/11/04, 521 nm o = 35o, Chl = 0.1 mg/m3 Average of 4 images (plus 2 Sides) Lu=0.64 W/(cm2 sr nm) Qu = 3.72, u = 0.44

  8. Important to understandthe effect of environmental noise in the radiance distribution images • Look at it from two views Average Normalized St. Dev.

  9. Alternatively… % Std. Dev. Histogram. Illustrates that it is unlikely that Std Dev. of pixel matchups with a model will be better than 3% or so…..radiance distribution just isn’t that stable.

  10. Extent of Data Set Used(in this study)

  11. Model-Data comparison Define: (Note: Chl= 0.11 mg/m3, 11o<o<40o)

  12. Error vs Chl, each point is one day Red dots, error; red bars, std; blue dots measurement std

  13. Error vs zenith angle (only displaying 412 nm, others show nothing significant)

  14. Conclusions • To date, within the accuracy/environmental noise of data, Morel et al. 2002 model works. • Need more data in Chl range from 0.4 to 10 mg/m3. • Need another alternative in Case II waters, have more turbid data sets to look at this problem. • Polarization? Have modified NuRADS to provide upwelling polarization data (see poster by Souidia et al.)

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