Hyperspectral radiometric observation of the northeast Arabians Sea during April 2006
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Photonirvachak
J. Indian Soc. Remote Sens. (March 2008) 36:13–25
RESEARCH ARTICLE
Hyperspectral Radiometric Observation of the Northeast Arabians Sea during April 2006 R. K. Sarangi, S. Singh, R. M. Dwidevi and S. G. P. Matondkar
Received: 15 December 2006 / Accepted: 10 November 2007
Keywords
Hyperspectral Radiometer · Northeast Arabian sea · Pigments · Trichodesmium bloom
Abstract Parameters were retrieved from the hyperspectral radiometer like upwelling and downwelling radiance (Lu and Ed) upwelling and downwelling attenuation (K-Lu and K-Ed) for 9 stations in the northeast Arabian Sea between 16–26 April 2006. Data was analyzed for 5 offshore and
R. K. Sarangi1 (), S. Singh2, R. M. Dwidevi1 and S. G. P. Matondkar3 1 Marine & Earth Sciences Group, Space Applications Center, Ahmedabad - 380 015, India 2 Present address: Aryabhatta Research Institute of Observational Sciences, Nainital, Uttarakhand, India 3 Biological Oceanography Division, National Institute of Oceanography (NIO), Goa, India e-mail: [email protected]
4 coastal stations of the cruise SS-244, on board FORV “Sagar Sampada” between latitude 9–22oN and longitude 68–74o E. The peak for all parameters was observed to be different respectively for depths 1, 5, 10, 20, 30, 40, 50 meters in coastal and offshore stations. Each peak in the respective wavelength is due to a particular composition; phytoplankton pigments have spectral peaks at 443, 490, 555, 670 nm, suspended matter, sediments have peaks at 630 and 670 nm. Detailed analysis with High Performance Liquid Chromatography (HPLC) data and comparison with the water composition of our hyperspectral radiometer results show that the marine cyanophyte, Trichodesmium bloom produces high pigment concentrations of chlorophyll-a, zeaxanthin, β-carotene and pheophytin and their absorptions are interpreted at wavelengths 443, 490, 515 and 536 nanometers, respectively. A dip around 515 nm was seen in the Ed and Lu profiles in our study.
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Introduction Recent advances in hydrologic optics offer potential for quantitative maps of the inherent optical properties, which can be inverted into optically significant constituents (Aarup et al., 1996). Robust estimates for phytoplankton community composition could be achieved but required constraints on the inversion that phytoplankton dominate the red light absorption (Mobley, 1994). The best profile datasets having tilt angle less than 200 during our cruise measurements have been accounted for study and have been plotted versus depth. Algorithms have been developed to relate remotely sensed parameters to in-water constituents including chlorophyll concentration and water constituents (Chang et al., 2003). It is suggested that traditional water mass markers might be complimented with standard biological measurements such as chlorophyll as an additional dimension would improve resolving water types in parameter space (Tomkczak, 1999). Most of the coastal systems reflect the optical contributions of numerous inwater constituents—water, phytoplankton, CDO
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