AN IMPROVED LIDAR METHOD FOR MONITORING SURFACE WATERS - EXPERIMENTS IN THE LABORATORY

Lidar monitoring of surface waters is usually applied to fluorescent s ubstances like phytoplankton, yellow substances and oil. A lidar metho d is introduced which allows the measuring of the total attenuation co efficient at the laser wavelength considering also nonfluorescent subs tances besides fluorescent ones. Two signals are measured: first the t otal fluorescence lidar signal L, which is characterized by long path- lengths of the laser radiation in the water column, and second, the fl uorescence F, which originates from the first layers immediately below the water surface. A simple experiment in the laboratory was performe d using a nitrogen laser. Water samples containing algae and varying a mounts of humic and ligninesulfonic acids were investigated. Synchrono usly the attenuation coefficients were measured. The F/L ratio yielded the total attenuation at the laser wavelength. Good correlations betw een the conventional and the lidar-derived attenuation coefficients we re achieved described by squared correlation coefficients of R-2 > 0.9 5. The F/L ratio seems to be a good tool in lidar monitoring of waters .