Validation of in situ inherent optical properties in the sargasso sea.

In situ inherent optical properties (IOP) determinations from the U.S. JGOFS Bermuda Atlantic Time-Series (BATS) made from 1994 to 1996 are used to develop processing and correction methods for clear natural waters. Upper bound estimates of precision are 0.0066 and 0.0018 m(-1) for non-water beam attenuation (c-c(w)(lambda)) and absorption coefficient (a-a(w)(lambda)) respectively. These are determined by examining the intracruise variability at 190m depth where minimum natural variations exist. The final corrected IOP values show consistent patterns with time, depth and wavelength. A strong correlation is observed between measured beam attenuation and absorption coefficient at 440 nm in the upper 50m (r(2)=0.71). Whereas lower correlation is observed between the scattering coefficient (b-b(w)(440)) and absorption coefficient (r(2)=0.52). In the upper 50m layer, measured values of a-a(w)(440) in the upper 50m compare well with chlorophyll-based bio-optical model ((r(2)=0.71, slope=1.17). However measured values of c-c(w)(440) and b-b(w)(440) do not compare well with the modeled values (r(2)=0.38 & 0.25, respectively). In particular, the measured b/a(440) shows an inverse relationship compared with estimated b/a(440) ratio in the upper 50m.