Subsurface Ocean Signals from an Orbiting Polarization Lidar

Detection of subsurface returns from the Cloud-Aerosol Lidarwith Orthogonal Polarization (CALIOP) on the Cloud-Aerosol Lidarand Infrared PathfinderSatellite Observation (CALIPSO) satellite were demonstrated. Despite the coarse range resolution of this aerosol lidar, evidence of subsurface scatteringwas observed as a delay and broadening of the cross-polarized signal relative to the co-polarized signal in the three near-surface range bins. These two effects contributed to an increased depolarizationat the nominal depth of 25 m. These features were all correlated with near-surface chlorophyll concentrations. An increase in the depolarizationwas also seen at a depth of 50 m under certain conditions, suggesting that chlorophyll concentration at that depth could be estimated if an appropriate retrieval technique can be developed. At greater depths, the signal is dominated by the temporal response of the detectors, which was approximated by an analytical expression. The depolarizationcaused by aerosols in the atmosphere was calculated and eliminated as a possible artifact.