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This page contains a single entry from the blog posted on February 19, 2014 1:30 PM.

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Seminar: Wednesday, Feb. 19 at 3:30 pm

Light, Ocean, and Life
Pengwang Zhai
SSAI, NASA Langley Research Center

Phytoplankton are unicellular organisms that are responsible for half of all photosynthetic activity on Earth. According to their functional types, phytoplankton are divided into several different conceptual groups that include calcifiers, nitrogen fixers, DMS producers and silicifiers. Coccolithophores belong to the calcifier group which plays important roles in global carbon cycle processes. When proper nutrition and light conditions are met, phytoplankton can produce massive blooms, which have large environmental impacts. I am primarily interested in how light interacts with particles, particularly phytoplankton and other oceanic particles, and how light can be used to remote sense and monitor ocean water optical properties. In this talk I will cover three general aspects of my research interests: light scattering, radiative transfer, and optical remote sensing. Light scattering studies the interaction of light with single particles within the classical electromagnetic theory and linear optics. Radiative transfer theory covers light field multiply scattered within turbid media consisting of individual particles. It is understood that optical properties of single particles are known knowledge in radiative transfer theory. Generally radiative transfer theory assumes incoherent scattering, which means that there is no systematic phase correlation among light waves scattered by a group of particles. Nonetheless, coherent scattering is significant in coherent backscattering and other phenomena. Optical remote sensing is to use light scattered by particles, singly or multiply, to retrieve information about particles’ properties. In other words, light scattering and radiative transfer theories are building blocks and diagnostic tools for optical remote sensing. I will present two examples of my research efforts in each of the three theoretical categories. In light scattering, the examples are invisible particles for monostatic lidar/radar detections and simulation of light scattering by nonspherical coccolithophores. In radiative transfer theory section, I will cover how polarization is treated and two methods are presented to solve light field in a turbid medium: Monte Carlo and the successive order of scattering. In the optical remote sensing section, two applications of polarized radiative transfer solutions are given for ocean color and aerosol remote sensing.

Location: Physics Bldg., Room 401