ABSTRACT
Chlorophyll-a specific light volume scattering functions (VSFs) by cultured phytoplankton in visible spectrum range is presented. Chlorophyll-a specific VSFs were determined based on the linear least squares method using a measured VSFs with different chlorophyll-a concentrations. We found obvious variability of it in terms of spectral and angular shapes of VSF between cultures. It was also presented that chlorophyll-a specific scattering significantly affected on spectral variation of the remote sensing reflectance, depending on spectral shape of b. This result is useful for developing an advance algorithm of ocean color remote sensing and for deep understanding of light in the sea.
Subject(s)
Chlorophyll/analysis , Phytoplankton/chemistry , Spectrum Analysis/methods , Algorithms , Chlorophyll A , Color , Environmental Monitoring/methods , Scattering, RadiationABSTRACT
Backscattering coefficients are frequently estimated from light scattering at one backward angle multiplied by a conversion factor. We determined that the shapes of the volume scattering functions (VSFs), particularly for scattering angles larger than 170°, cause significant variations in the conversion factor at 120°. Our approach uses the ratio of scattering at 170° and at 120°, which is a good indicator of the shape differences of the VSFs for most oceanic waters and wavelengths in the visible range. The proposed method provides significant accuracy improvement in the determination of the backscattering coefficients with a prediction error of 3% of the mean.
Subject(s)
Scattering, Radiation , Algorithms , Environmental Monitoring/methods , Light , Nephelometry and Turbidimetry , Optics and Photonics , Particulate Matter , Phytoplankton , Remote Sensing Technology , Reproducibility of Results , Water MicrobiologyABSTRACT
We present a novel optical approach to measure the volume scattering function (VSF) by image detection. The instrument design, based upon a combination of two reflectors, uses a unique measurement principle and allows the rapid simultaneous determination of scattering at a wide range of angles. The advantages of the newly developed scattering meter are that: 1) it can determine the scattering function from 8° to 172° at 1° intervals without changing the sensitivity of the detector, without moving any optical parts, and can do so within a few seconds, 2) the unique optical design facilitates determination of the spectral VSF over the full visible spectrum, i.e. it can obtain the VSF at a specific wavelength with an optional wavelength-resolution. Measurements under controlled conditions for the assessment of the instrument agreed well with theoretically predicted scattering functions. Measurements with cultured phytoplankton of different species revealed a significant variety of the VSF together with spectral variation. The observed results will stimulate and improve radiative transfer and/or two-flow models of light in the ocean, which is an important role for ocean color remote sensing algorithm development, particularly for coastal regions.
ABSTRACT
We developed a new illumination method called the simultaneous illumination method. This method does not require synchronization between light sources and sensor signals, which drastically simplifies the instrumentation. As a proof-of-concept, we applied this method to an oceanographic fluorometer. In principle, using this method, one can easily increase the number of characterized emission wavelengths by mounting optical sensors for as many emission wavelengths as needed. Our fluorometer has two emission-wavelength channels and twelve excitation wavelengths. The aim of this prototype is to demonstrate a viable in situ N-channel emission fluorometer with multiple wavelengths of excitation, which has not been previously realized.
