Remote sensing of coastal waters by airborne lidar and satellite radiometer Part 2: Measurements

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Abstract
Active and passive remote sensing techniques for measurement of oceanic constituents have been compared using the ADRIA'84 dataset. A new method has been developed to retrieve the amount of nonchlorophyllous particles by airborne lidar measurements at three wavelengths. If the lidar measurements of chlorophyll-a and Gelbstoff are calibrated by in situ measurements, the fluorescence efficiencies can be estimated, Specific extinction coefficients for chlorophyll-a and nonchlorophyllous particles for the northern Adriatic Sea have been derived by comparing in situ and underwater irradiance measurements with radiative transfer calculations, using the ocean-atmosphere model by Fischer (1983). For the Coastal Zone Colour Scanner (CZCS), an algorithm for chlorophyll-a measurements was derived. The comparison with chlorophyll-a lidar measurements shows that different scales are resolved by both instruments. The CZCS-chlorophyll-a concentrations are influenced by Gelbstoff and nonchlorophyllous particles. It is possible to use airborne lidar measurements of chlorophyll-a for calibrating spaceborne radiometers, if the fluorescence efficiency of chlorophyll-a is known and if the lidar itself is calibrated. The comparison between Advanced Very High Resolution Radiometer (AVHRR) sea surface temperatures and CZCS measurements indicates that mesoscale structures in the ocean are much better indicated by measurements in the visible spectrum. Mesoscale structures are often masked by the warming of the ocean top layer when measuring in the infrared.