Characterizing the vertical diffuse attenuation coefficient for downwelling irradiance in coastal waters: Implications for water penetration by high resolution satellite data

To characterize the water column, the diffuse attenuation coefficient of downwelling inradiance, K-d(z,lambda) (m(-1)) is one of the most important optical properties of seawater. The purpose of this research was to determine the downwelling diffuse attenuation coefficient of water around Roatan Island, Honduras. In situ K-d analysis showed low attenuation coefficient values in green and blue and increased exponentially after 570 nm. The blue, green and red portion of the spectrum showed a K-d value of 0.138, 0.158, and 0.503 m(-1), respectively. Error analysis revealed a significantly high uncertainty in the red region (600-700 nm) and, as expected, low estimation uncertainty in blue and green. When compared with IKONOS derived K-d (490 nm), it was observed that the differences were negligible, being 0.0084 and 0.0054 m(-1) for station #1 and #2, respectively. Based on the fact that 90% of the diffused reflected light from a water body comes from a surface layer of water of depth 1/K-d, the results showed that a typical satellite sensor (such as IKONOS) can penetrate up to 8 in in the blue band, 6 in in green, and 2 m in the red region. (C) 2005 International Society for Photogrammetry and Remote Sensing, Inc. (ISPRS). Published by Elsevier B.V. All rights reserved.