Comparison of measured inherent optical properties with estimates determined from reflectance in coastal waters off Cape Hatteras North Carolina USA

摘要

The ability to acquire information about inherent optical properties such as total spectral absorption (a($lambda@), m$+$MIN@1$/) and scattering (b($lambda@), m$+$MIN@1$/) from reflectance properties of oceanic waters is fundamental to the development of remote sensing algorithms. While considerable success has been achieved in relatively clear oceanic waters, inversion methods to determine a($lambda@) and b($lambda@) in conjunction with profiles of in situ radiance reflectance at various locations off Cape Hatteras, North Carolina during spring 1996. Our objective was to evaluate measurment and model closure among the different methods that were applied. Spectral a and b were determined using a WETLabs ac-9. Independent estimates of a were also determined in discrete samples using a spectrophotometer. In situ upwelling radiance (L$-u$/) and downwelling irradiance (E$-d$/) were determined using a Satlantic SeaWiFS Profiling Multichannel Radiometer. Inverse methods provided estimates of a and b from reflectance (L$-u$//E$-d$/). For the mid- shelf station characterized by relatively low b/a ratios, agreement among the different methods for estimating a($lambda@) was quite good. At the inner shield station, higher b/a ratios were encountered and larger discrepancies were observed between the different methods. The results illustrate the utility of multi-faceted measurement strategies for evaluating the reliability of estimates of optical properties.