Japan Geoscience Union Meeting 2015

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International Session (Oral)

Symbol A (Atmospheric and Hydrospheric Sciences) » A-CG Complex & General

[A-CG09] Satellite Earth Environment Observation

Thu. May 28, 2015 11:00 AM - 12:45 PM 301B (3F)

Convener:*Riko Oki(Japan Aerospace Exploration Agency), Tadahiro Hayasaka(Graduate School of Science, Tohoku University), Kaoru Sato(Department of Earth and Planetary Science, Graduate School of Science, The University of Tokyo), Masaki Satoh(Atmosphere and Ocean Research Institute, The University of Tokyo), Nobuhiro Takahashi(National Institute of Information and Communications Technology), Yoshiaki HONDA(Center for Environmental Remote Sensing, Chiba University), Kenlo Nasahara(Faculty of Life and Environmental Sciences, University of Tsukuba), Takashi Nakajima(Tokai University, School of Information Science & Technology, Dept. of Human & Information Science), Taikan Oki(Institute of Industrial Science, The University of Tokyo), Tatsuya Yokota(National Institute for Environmental Studies), Yukari Takayabu(Atmosphere and Ocean Research Institute, the University of Tokyo), Hiroshi Murakami(Earth Observation Research Center, Japan Aerospace Exploration Agency), Hajime Okamoto(Kyushu University), Chair:Misako Kachi(Earth Observation Research Center, Japan Aerospace Exploration Agency)

12:30 PM - 12:45 PM

[ACG09-25] Ocean colour remote sensing of marine euphotic depth

*Takafumi HIRATA1 (1.Faculty of Environmental Earth Science, Hokkaido University)

Keywords:Ocean Colour, Satellite Remote Sensing, Euphotic Depth, Photosynthetically Available Radiation

The euphotic depth is defined as a depth where Photosynthetically Available Radiation (PAR) at the sea surface decreased by 1% during its propagation into a water column. While a large amount of ocean colour signal detected by satellite originates from the ocean surface and cannot directly retrieve the euphoric depth, it is a challenge to estimate the euphotic depth by satellite remote sensing. In addition, PAR is defined as the radiance integrated over a range of wavelength (often 400-700nm), while the operational ocean colour satellites only observe the radiance at discrete wavelengths. Thus, it is even a challenge to estimate PAR, hence, the euphotic depth eventually. Furthermore, phytoplankton in the ocean, which is a photosynthetic organism, utilizes radiance at the all solid angles around it for photosynthesis, therefore consideration of radiance at all solid angles is a particular importance in considering the attenuation of PAR when retrieving the euphoric depth, while the ocean colour satellite detects radiance originating only from a certain solid angle, thus showing another challenge. In order to solve these problems for the satellite estimation of the euphotic depth, extensive radiative transfer simulations were conducted. Results show (1) the diffuse attenuation of PAR at the sea surface has a certain relationship with that averaged over euphotic zones, (2) the diffuse attenuation of PAR, which is wavelength-integrated property, can be estimated from an ocean colour measurement at a discrete wavelength, (3) the diffuse attenuation of PAR originating from the all solid angles has a relationship with that of PAR originating from a certain range of solid angles. Using these findings above, a satellite ocean colour algorithm was developed to estimate the euphotic depth. In this presentation, details of the methodology will be demonstrated, and global variability of the euphoric depth will be shown.