AIRBORNE LASER-INDUCED OCEANIC CHLOROPHYLL FLUORESCENCE - SOLAR-INDUCED QUENCHING CORRECTIONS BY USE OF CONCURRENT DOWNWELLING IRRADIANCE MEASUREMENTS

Airborne laser-induced (and water Raman-normalized) spectral fluoresce nce emissions from oceanic chlorophyll were obtained during variable d ownwelling irradiance conditions induced by diurnal variability and pa tchy clouds. Chlorophyll fluorescence profiles along geographically re peated inbound and outbound flight track lines, separated in time by s imilar to 3-6 h and subject to overlying cloud movement, were found to be identical after corrections made with concurrent downwelling irrad iance measurements. The corrections were accomplished by a mathematica l model containing an exponential of the ratio of the instantaneous-to -average downwelling irradiance. Concurrent laser-induced phycoerythri n fluorescence and chromophoric dissolved organic matter fluorescence were found to be invariant to downwelling irradiance and thus, along w ith sea-surface temperature, established the near constancy of the oce anic surface layer during the experiment and validated the need for ch lorophyll fluorescence quenching corrections over wide areas of the oc ean.