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537 results on '"Franz, Bryan A."'

203. Some Insights of Spectral Optimization in Ocean Color Inversion

Author

NAVAL RESEARCH LAB STENNIS DETACHMENT STENNIS SPACE CENTER MS OCEANOGRAPHY DIV, Lee, Zhongping, Franz, Bryan, Shang, Shaoling, Dong, Qiang, Arnone, Robert, NAVAL RESEARCH LAB STENNIS DETACHMENT STENNIS SPACE CENTER MS OCEANOGRAPHY DIV, Lee, Zhongping, Franz, Bryan, Shang, Shaoling, Dong, Qiang, and Arnone, Robert

Abstract

Over the past few decades, various algorithms have been developed for the retrieval of water constituents from the measurement of ocean color radiometry, and one of those approaches is spectral optimization. This approach defines an error function (or cost function) between the observed spectral remote sensing reflectance and an estimated spectral remote sensing reflectance over the range of observed wavelengths, with the latter modeled using a few variables that represent the optically active properties (such as the absorption coefficient of phytoplankton and the backscattering coefficient of particles). The values of the variables when the error function reaches a minimum are the optimized properties. The applications of this approach implicitly assume that there is only one global minimum condition, and that any local minimum (if exist) can be avoided through the numerical optimization scheme Here, with data from numerical simulations, we show the shape of the error surface as a mechanism to visualize the solution space for the model variables. Further, using two established models as examples, we demonstrate how the solution space changes under different model assumptions as well as the impacts on the quality of the retrieved water properties.

Published
2011

204. Satellite-detected fluorescence reveals global physiology of ocean phytoplankton

Author

Behrenfeld, Michael J., Westberry, Toby K., Boss, Emmanuel S., O'Malley, Robert T., Siegel, David A., Wiggert, Jerry D., Franz, Bryan A., McClain, Charles R., Feldman, G. C., Doney, Scott C., Moore, J. Keith, Dall'Olmo, Giorgio, Milligan, A. J., Lima, Ivan D., Mahowald, Natalie M., Behrenfeld, Michael J., Westberry, Toby K., Boss, Emmanuel S., O'Malley, Robert T., Siegel, David A., Wiggert, Jerry D., Franz, Bryan A., McClain, Charles R., Feldman, G. C., Doney, Scott C., Moore, J. Keith, Dall'Olmo, Giorgio, Milligan, A. J., Lima, Ivan D., and Mahowald, Natalie M.

Abstract

© 2009 The Authors. This is an open-access article distributed under the terms of the Creative Commons Attribution 3.0 License. The definitive version was published in Biogeosciences 6 (2009): 779-794, doi: 10.5194/bg-6-779-2009, Phytoplankton photosynthesis links global ocean biology and climate-driven fluctuations in the physical environment. These interactions are largely expressed through changes in phytoplankton physiology, but physiological status has proven extremely challenging to characterize globally. Phytoplankton fluorescence does provide a rich source of physiological information long exploited in laboratory and field studies, and is now observed from space. Here we evaluate the physiological underpinnings of global variations in satellite-based phytoplankton chlorophyll fluorescence. The three dominant factors influencing fluorescence distributions are chlorophyll concentration, pigment packaging effects on light absorption, and light-dependent energy-quenching processes. After accounting for these three factors, resultant global distributions of quenching-corrected fluorescence quantum yields reveal a striking consistency with anticipated patterns of iron availability. High fluorescence quantum yields are typically found in low iron waters, while low quantum yields dominate regions where other environmental factors are most limiting to phytoplankton growth. Specific properties of photosynthetic membranes are discussed that provide a mechanistic view linking iron stress to satellite-detected fluorescence. Our results present satellite-based fluorescence as a valuable tool for evaluating nutrient stress predictions in ocean ecosystem models and give the first synoptic observational evidence that iron plays an important role in seasonal phytoplankton dynamics of the Indian Ocean. Satellite fluorescence may also provide a path for monitoring climate-phytoplankton physiology interactions and improving descriptions of phytoplankton light use efficiencies in ocean productivity models., This work was supported by grants from the NASA Ocean Biology and Biogeochemistry Program and the NSF Biological Oceanography Program.

Published
2009

207. Generalized ocean color inversion model for retrieving marine inherent optical properties

Author

Werdell, P. Jeremy, primary, Franz, Bryan A., additional, Bailey, Sean W., additional, Feldman, Gene C., additional, Boss, Emmanuel, additional, Brando, Vittorio E., additional, Dowell, Mark, additional, Hirata, Takafumi, additional, Lavender, Samantha J., additional, Lee, ZhongPing, additional, Loisel, Hubert, additional, Maritorena, Stéphane, additional, Mélin, Fréderic, additional, Moore, Timothy S., additional, Smyth, Timothy J., additional, Antoine, David, additional, Devred, Emmanuel, additional, d’Andon, Odile Hembise Fanton, additional, and Mangin, Antoine, additional

Published
2013
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208. On-orbit calibration of SeaWiFS

Author

Eplee, Robert E., primary, Meister, Gerhard, additional, Patt, Frederick S., additional, Barnes, Robert A., additional, Bailey, Sean W., additional, Franz, Bryan A., additional, and McClain, Charles R., additional

Published
2012
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210. VIIRS on-orbit calibration for ocean color data processing

Author

Eplee, Robert E., primary, Turpie, Kevn R., additional, Fireman, Gwyn F., additional, Meister, Gerhard, additional, Stone, Thomas C., additional, Patt, Frederick S., additional, Franz, Bryan A., additional, Bailey, Sean W., additional, Robinson, Wayne D., additional, and McClain, Charles R., additional

Published
2012
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212. Ocean Colour Climate Change Initiative — Approach and initial results

Author

Sathyendranath, Shubha, primary, Brewin, Bob, additional, Mueller, Dagmar, additional, Doerffer, Roland, additional, Krasemann, Hajo, additional, Melin, Frederic, additional, Brockmann, Carsten, additional, Fomferra, Norman, additional, Peters, Marco, additional, Grant, Mike, additional, Steinmetz, Francois, additional, Deschamps, Pierre-Yves, additional, Swinton, John, additional, Smyth, Tim, additional, Werdell, Jeremy, additional, Franz, Bryan, additional, Maritorena, Stephane, additional, Devred, Emmanuel, additional, Lee, ZhongPing, additional, Hu, Chuanmin, additional, and Regner, Peter, additional

Published
2012
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228. A VIIRS ocean data simulator

Author

Robinson, Wayne D., primary, Patt, Frederick S., additional, Franz, Bryan A., additional, Turpie, Kevin R., additional, and McClain, Charles R., additional

Published
2009
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248. The continuity of ocean color measurements from SeaWiFS to MODIS

Author

Franz, Bryan A., primary, Werdell, P. J., additional, Meister, Gerhard, additional, Bailey, Sean W., additional, EpleeJr., Robert E., additional, Feldman, Gene C., additional, Kwiatkowskaa, Ewa, additional, McClain, Charles R., additional, Patt, Frederick S., additional, and Thomas, Donna, additional

Published
2005
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249. SIMBIOS program in support of ocean color missions: 1997-2003

Author

Fargion, Giulietta S., primary, Franz, Bryan A., additional, Kwiatkowska, Ewa J., additional, Pietras, Christophe M., additional, Bailey, Sean W., additional, Gales, Joel, additional, Meister, Gerhard, additional, Knobelspiesse, Kirk D., additional, Werdell, Jeremy, additional, and McClain, Charles R., additional

Published
2003
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