Karenia brevis (K. brevis) blooms are of great interest and have been commonly reported throughout the Gulf of Mexico. In this study we propose a detection technique for blooms with low backscatter characteristics, which we name the Red Band Difference (RBD) technique, coupled with a selective K. brevis bloom classification technique, which we name the K. brevis Bloom Index (KBBI). These techniques take advantage of the relatively high solar induced chlorophyll fluorescence and low backscattering of K. brevis blooms. The techniques are applied to the detection and classification of K. brevis blooms from Moderate Resolution Imaging Spectroradiometer (MODIS) ocean color measurements off the Gulf of Mexico. To assess the efficacy of the techniques for detection and classification, simulations, including chlorophyll fluorescence (assuming 0.75% quantum yield) based on K. brevis blooms and non-K. brevis blooms conditions were performed. These show that effective bloom detection from satellite measurements requires a threshold of RBD>0.15W/m(2)/microm/sr, corresponding to about 5mg/m(3) of chlorophyll. Blooms can be detected at lower concentration by lowering the RBD threshold but false positives may increase. The classification technique is found most effective for thresholds of RBD>0.15W/m(2)/microm/sr and KBBI>0.3*RBD. The techniques were applied and shown to be effective for well documented blooms of K. brevis in the Gulf of Mexico and compared to other detection techniques, including FLH approaches. Impacts of different atmospheric corrections on results were also examined.
Harmful Algal Blooms (HABs) can lead to severe economical and ecological impacts particularly in the coastal areas and can threaten human and marine health. About three-quarter of these toxic blooms are caused by dinoflagellates species which are well known to migrate vertically. During the day, they migrate up to the surface for photosynthesis, and consequently, their dense aggregations produce strong bio-optical signals that are detectable by space borne optical satellite sensors. In this study we use our recently developed low backscattering bloom detection technique, the Red Band Difference (RBD), to detect various dinoflagellates blooms using both MODIS (Moderate Resolution Imaging Spectroradiometer) and MERIS (Medium Resolution Imaging Spectrometer) data and present the results which confirm the potentials of the RBD technique. Here we present examples of bloom detection in waters off Gulf of Mexico, Monterey Bay, South Africa, and East China Sea.
This study proposes two tellurite-based PCFs whose are OSOC-PCF (Octa-Spiral with Octagonal Cladding PCF) and DSHC-PCF (Dodeca-Spiral with Hexagonal Cladding PCF) designs with higher nonlinearity and higher birefringence. Result comparisons of proposed PCFs are mentioned and demonstrated in this research study. By applying the finite element method with the assistance of COMSOL Multiphysics, we have investigated and simulated guiding properties like nonlinear coefficient, birefringence, dispersion, bending effect, confinement loss, power fraction, effective material loss. Comparing both designs, the highest nonlinearity is gained by OSOC-PCF reaches up to 7333 W −1 Km −1 around 1.55 μm of wavelength and obtained birefringence of 5.85×10 −2 wherein, a slight confinement loss occurs. The alluded PCFs possess an upstanding structure that associates operating an easy fabrication process. The convenience of propounded PCFs has plenty of purposes in polarization maintenance, optical communication, faster data communication, and super-continuum generation.
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