Physics 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)

Physics 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 E d, a and b b.

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

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

Physics 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 b b variation with Chl. –Calculation uses spheroids, and not spheres (which can be anomalous in the backscattering direction.

Physics 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.

Physics Example image and reduced product AOPEX, 8/11/04, 521 nm  o = 35 o, Chl = 0.1 mg/m 3 Average of 4 images (plus 2 Sides) L u =0.64  W/(cm 2 sr nm) Q u = 3.72,  u = 0.44

Physics Important to understand the effect of environmental noise in the radiance distribution images Look at it from two views AverageNormalized St. Dev.

Physics 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.

Physics Extent of Data Set Used (in this study)

Physics Model-Data comparison Define: (Note: Chl= 0.11 mg/m 3, 11 o <  o <40 o )

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

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

Physics Conclusions To date, within the accuracy/environmental noise of data, Morel et al model works. Need more data in Chl range from 0.4 to 10 mg/m 3. 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.)