Oceanic lidar: radiative transfer in the atmosphere at operating altitudes from 100 m to 100 km

The feasibility of measuring water-column parameters of the sea with a fluorescence lidar under daylight conditions and at flight altitudes between 100 m and 100 km is studied by modeling the atmospheric radiative transfer. Parameters to be measured are fluorescence of gelbstoff and chlorophyll and Raman scattering of water molecules. A cloudless and stratified atmosphere with various conditions of near-surface visibility and ozone concentration is taken into consideration. Solar zenith angles are varied between 0° and 60°. Lidar specifications are set to 1 J output energy, 10 ns pulse duration, 0.1 mrad beam divergence, 0.1 mrad detection angle, and 400 cm(-1) detection bandwidth. Signal recovery is carried out over the effective pulse length of the returned signal, which is roughly 20-30 ns. Sensor zenith angles are set between 0° and 60°. As a result of the study the recommended range of excitation wavelengths for high altitudes should be chosen between 350 and 400 nm. Under these circumstances, and with the iven laser and sensor specifications, oceanic lidar measurements should also be possible at flight altitudes of up to 100 km under clear visibility conditions, even at noon.