Shipboard oceanographic fluorescence lidar development and evaluation based on measurements in Antarctic waters

The prototype of a shipboard lidar for oceanographic applications uses the 355 nm wavelength of a Nd:YAG-Laser to excite fluorescence of gelbstoff and chlorophyll in seawater. The lidar was installed on board the research vessel Polarstern at the end of 1996 during cruise ANT XIV/2. Measurements were carried out around the South Shetland Islands and in the Drake Passage between South America and the Antarctic Peninsula. Remotely measured depth profiles of the beam attenuation coefficient in the upper water column were derived from time resolved measurements of water Raman scattering. In the same way, depth profiles of gelbstoff and chlorophyll were derived from laser-induced fluorescence signals. These depth profiles were continuously taken while the ship was underway with a penetration depth of up to 40 m, depending on the detection wavelength and turbidity of the water. The data are compared with in situ fluorescence measurements. Limitations and advantages of remotely measured lidar profiles and in situ measurements with submerged probes are discussed.