Tower-based radiometric observations at a coastal site in the Baltic Proper

An autonomous above-water radiometer was operated during the summer of 2005 on the Gustaf Dale´n Lighthouse Tower (GDLT) off the Swedish coast in the Baltic Proper. Normalized water leaving radiances, LWN(l), produced from measurements performed with the autonomous system at various center-wavelengths l in the 412e675 nm spectral range, were applied within the context of water quality monitoring and satellite ocean color validation activities. Specifically these in situ radiometric data were used to determine the chlorophyll a concentration through a regional band-ratio algorithm and to assess LWN(l) derived from top-of-atmosphere Moderate Resolution Imaging Spectroradiometer (MODIS) observations. The in situ measurements collected during a bloom occurring in July 2005 were also used to investigate the spectral and small scale temporal-spatial variability of LWN(l) in the presence of cyanobacteria.