Results

1. Introduction • Spectral radiance is one of the fundamental quantities of interest in the field of ocean optics (Kirk, 1989; Mobley, 1994). • Radiance, L(q,F,l, z), is defined as the radiant flux at a specified point with units of W (or quanta s-1) m-2 sr-1 nm-1. • The spectral shape and magnitude of radiance is dependent on the influx of solar radiation at the sea surface and the optical properties of the water column. • Upwelling radiance, Lu(q,F,l, z), is the radiance of an upwelling light field. r2 = 0.96 l=412 442 490 532 555 590 682 Percent Difference 14.70 12.16 11.92 15.93 18.83 27.93 41.04 r2 = 0.95 l=412 442 490 532 555 590 682 Percent Difference 17.62 19.39 17.19 9.52 11.33 19.97 12.11 • Importance • Quantifying ocean color/remote sensing • (Lw(l,0+) is water-leaving radiance and • Ed(l,0+) is solar spectral irradiance) • Chlorophyll concentration • (O’Reilly et al., 1998) • Spectral backscattering coefficient • Spectral absorption coefficient • Subsurface features • (Barnard et al., 2000) • Bottom type • Bathymetry • Water column visibility • Photosynthesis r2 = 0.99 l=412 442 490 532 555 590 682 Percent Difference 22.77 19.02 18.63 19.28 24.04 19.54 31.21 r2 = 0.99 l=412 442 490 532 555 590 682 Percent Difference 24.08 17.20 13.28 14.32 20.63 16.16 19.44 • Problems • Remote sensing • Atmospheric corrections, clouds • Extrapolation of region-specific to global ocean color algorithms • Determination of water column vertical structure • In situ measurements • Measurements of Lu(l,z) rather than the desired Lw(l,0+) • Surface roughness effects • (Toole et al., 2000) • Self-shading (Leathers et al., 2000) • Surface biological effects • (Cullen and Lewis, 1995) • Scattering phase functions • (Mobley et al., 2002) • Raman scattering (Gordon, 1999) • Study Site • LEO-15 site on the New Jersey continental shelf • New York Bight and Middle Atlantic Bight • Waters less than 25 m deep • Physics characterized by upwelling, small-scale eddies, riverine and estuarine inputs, fronts, coastal jets, tides, etc. • Optics characterized by phytoplankton blooms, turbidity fronts, terrestrial CDOM, bottom resuspension, etc. Acknowledgements This work was supported by: Special thanks to Francois Baratange for engineering support and data processing and Bob Arnone for remote sensing images. Toward Closure of In Situ Upwelling Radiance in Coastal Waters Grace C. Chang1, Emmanuel Boss2, Curt Mobley3, Tommy D. Dickey1, and W. Scott Pegau2 1Ocean Physics Laboratory, University of California, Santa Barbara; 2Oregon State University, Corvallis, OR; 3Sequoia Scientific, Inc., Redmond, WA Contact Information: grace.chang@opl.ucsb.edu; http://www.opl.ucsb.edu/ Methods (1) Satlantic, Inc. SeaWiFS Profiling Multichannel Radiometer (SPMR) on the Suitcase package (l = 412, 442, 490, 532, 555, 590, and 682 nm) Used to calculate: for Lu(l,0.66m), Lu(l,0-m). The n-squared law for transmittance across sea surface used to calculate: where t ~ 0.98 and n ~ 1.34 (2) Satlantic, Inc. Hyperspectral Tethered Spectral Radiometric Buoy (HyperTSRB) l = 400 – 800 nm 3.3 nm bandwidth (3) Hydrolight 4.1 with measured absorption and attenuation (ac-9); CDOM absorption (filtered ac-9); chlorophyll a concentration (fluorometer); and volume scattering function Assumptions: - No Raman scattering - No bioluminescence - Default a*ph(l) - TSRB sky irradiance - Optically deep waters • Conclusions • Average Statistics • Lu(l,0.66m) TSRB and Hydrolight Results Lw(l,0+m) Lu(l,0.66m) Suitcase and Hydrolight Comparisons between Suitcase, HyperTSRB, and Hydrolight-derived Lu(l,0.66m), Lu(l,0-m), and Lw(l,0+m) for July 21 and 22, 2000 at locations 39.37oN, 74.21oW and 39.46oN, 74.26oW, left to right. Lw(l,0+m) • Differences in Lw(l,0+m) due to n-squared law of transmittance • Differences in blue wavelengths attributed to: • - Scattering correction for absorption • - Errors in VSF measurements (prototype instrument) • Differences in red wavelengths attributed to: • - Use of default chlorophyll-specific absorption coefficient in • Hydrolight modeling • Spectral shape of L(q,F,l, z) changes from nearshore to offshore due to changes in water type. References Barnard, A.H., A.D. Weidemann, W.S. Pegau, J.R.V. Zaneveld, J. W. Rhea, and C. O. Davis, Hyperspectral remote sensing imagery and the detection of subsurface features, Ocean Optics XV, 2000. Cullen, J.J. and M.R. Lewis, Biological processes and optical measurements near the sea surface: Some issues relevant to remote sensing, J. Geophys. Res., 100, 13,255-13,266, 1995. Gordon, H.R., Contribution of Raman scattering to water-leaving radiance: a reexamination, Appl. Opt., 38, 3166-3174, 1999. Kirk, J.T.O., The upwelling light stream in natural waters, Limnol. Oceanog., 34, 1410-1425, 1989. Leathers, R.A., T.V. Downes, and C.D. Mobley, Self-shading correction for upwelling sea-surface radiance measurements made with buoyed instruments, Opt. Exp., 8, 561-570, 2001. Mobley, C.D., Light and Water: Radiative Transfer in Natural Waters, Academic Press, San Diego, 592 pages, 1994. Mobley, C.D., L.K. Sundman, and E. Boss, Phase function effects on oceanic light fields, Appl. Opt., in press. O’Reilly, J.E., S. Maritorena, B.G. Mitchell, D.A. Siegel, K.L. Carder, S.A. Garver, M. Kahru, and C. McClain, Ocean color chlorophyll algorithms for SeaWiFS, J. Geophys. Res., 103, 24,937-24,953, 1998. Toole, D.A., D.A. Siegel, D.W. Menzies, M.J. Neumann, and R.C. Smith, Remote-sensing reflectance determinations in the coastal ocean environment: impact of instrumental characteristics and environmental variability, Appl. Opt., 39, 456-469, 2000. LEO-15 site Comparisons between Suitcase, HyperTSRB, and Hydrolight-derived Lu(l,0.66m), Lu(l,0-m), and Lw(l,0+m) for July 24 and 27, 2000 at locations 39.41oN, 74.20oW and 39.34oN, 74.08oW, left to right. Remote Sensing Reflectance Closure Sampling Locations Year 2000 Comparisons between Suitcase, TSRB, and Hydrolight-derived Rrs(l) for July 24, 2000 at locations 39.49oN, 74.19oW and 39.41oN, 74.20oW, left to right.