Remote sensing estimates of inherent optical properties in a coastal environment

High resolution aircraft remote sensing imagery and in situ optical data were coupled to characterize the spatial and temporal variability of the inherent optical properties in the near-surf zone off Fort Walton Beach, Florida in August 1994. Upwelling radiance measurements at SeaWiFS wavelengths were collected over a uniform, highly reflective white sand bottom at a ground resolution of 2..5 m using the CASI sensor (Compact Airborne Spectral Imager). Following atmospheric correction, the total remote sensing reflectance signal was partitioned into bottom and water volume reflectance components, using measurements of bottom albedo, water depth, and the diffuse attenuation coefficient at the time of the overflight. The water components were entered in the SeaWiFS biooptical model to derive spectral absorption and scattering coefficients. After applying minor algorithm and coefficient adjustments, model results compared favorably with in situ measurements. The biooptical model was subsequently applied to the aircraft imagery to describe the spatial distribution of absorption and scattering. Elevated absorption and particle scattering were observed over the sand bar and shoreward (a555=0.19 m−1, b555=0.7 m−1). The temporal variability of the inherent optical properties over a I-week period was similar to the spatial variability along a 500-in offshore transect.