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Curt Mobley is Guest Speaker in St. Petersburg
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![[alt text]](mobley.jpg)
Curt's "honorarium" for his three seminars was a guided trip to manatee country.
Owing to unseasonably warm December weather, he encountered no manatees but was happy
to see lots of great Florida geology. Here, he stands by spring waters bubbling to the surface
near the head of Potter Creek.
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The Center for Coastal and Regional Marine Studies (CCRMS) was pleased to welcome Curt Mobley to St.
Petersburg, FL, for a series of talks on December 12 and 13. Curt is Vice President and Senior Scientist at
Sequoia Scientific, Inc., in Seattle, WA. He is the author of the highly acclaimed text, "Light and Water: Radiative
Transfer in Natural Waters," as well as the Hydrolight radiative-transfer software package. In collaboration with
the College of Marine Science at the University of South Florida (USF St. Petersburg campus), the center
cohosted three seminars that were highly relevant to USGS research on benthic productivity and remote
sensing in shallow marine environments. These talks attracted a good turnout, with scientists attending not
only from CCRMS and USF, but also from Mote Marine Laboratory in Sarasota and the USGS Water Resources
office in Tampa.
Curt's first talk was titled "Phase Function Effects on Oceanic Light Fields." The phase function of a particle—
for example, a clay particle suspended in saltwater—can be thought of as describing the directions in which
incident photons are likely to be scattered upon interaction with the particle. Because scattering processes are
quite difficult to measure, the phase functions of various types of particles tend to be largely unknown. In this
talk, Curt discussed the various assumptions typically required when modeling scattering processes in natural
waters, as well as the implications of those assumptions. With an unusually comprehensive data set collected
during the U.S. Navy's Hyperspectral Coastal Ocean Dynamics Experiment, he demonstrated that using a
phase function with the correct backscatter fraction and overall shape is crucial to achieving model-data closure.
Curt's second talk was on the "Effects of Optically Shallow Bottoms on Upwelling Radiances." Drawing on his
experience with the U.S. Navy's Coastal Benthic Optical Properties field experiment, Curt discussed the
complexities of modeling remote-sensing reflectance and other optical quantities in shallow coastal environments.
In particular, he discussed and quantified the problems that arise when a shallow sea bottom is non-Lambertian
(that is, when light is not scattered equally in all directions after striking the bottom), when the bottom surface
is sloping, or when the bottom surface is of more than one bottom type (for example, both seagrass and
coralline sand). These conditions are particularly problematic for nonspecialists in radiative transfer, because
off-the-shelf radiative-transfer models typically rely on the assumptions of a Lambertian bottom reflector,
a flat bottom, and horizontal homogeneity. Curt's talk brought good news because he discussed how the
effects of these real-world complexities can be accounted for by users of Hydrolight or other computationally
efficient radiative-transfer models. These results are especially pertinent for USGS efforts to apply the tools
of remote sensing to coral reefs or other shallow aquatic environments.
Curt's third talk was on "Multi-disciplinary Applications of Radiative Transfer Modeling." Although radiative transfer
might seem at first glance to be a bit of an arcane topic, understanding and predicting how photons propagate
through natural waters actually have great relevance to a tremendously broad range of Earth-science topics.
Particularly pertinent to USGS interests, for example, is understanding how suspended sediment in estuarine
waters affects seagrass beds or how water depth influences remotely sensed images of coral reefs. In his
final talk, Curt outlined some basic principles of radiative-transfer modeling and provided many examples
of how this tool is currently being used by scientists in the fields of life, Earth, and ocean sciences.
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February 2002
in this issue:
cover story:
Santa Barbara Shorebirds
Northwest Australia
California Sea Otter
Stellwagen Bank NMS Web Site
Science Mentoring
Woods Hole Food Drive
CMGP Planning
Curt Mobley
Gulf of Mexico Integrated Database Workshop
Cooperative Agreements
Citation Classic
Mike Carr & Homa Lee
Netherlands Visiting Scientist
New Woods Hole Lab Van
Farewell
Woods Hole Visitor
New Woods Hole Staff
Postdoc Presents Seminar
February Publications List
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U. S. Department of the Interior | U.S. Geological Survey
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