Probing The Subsurface Ocean Processes Using Ocean Lidars

Subsurface profiling LIDAR systems extend our understanding of ocean processes "below" the ocean surface of SST and ocean color. Time-gated LIDAR backscattering intensity has been shown to define the bio-optical ocean layers and characterize subsurface processes. The interaction between the mixed layer depth (MLD) using vertical temperature structures and LIDAR optical layers provides a critical link between physical and bio-optical processes. We evaluated the capability of LIDAR penetration to reach the MLD on a global basis. Penetration depths of LIDAR were estimated using attenuation depths derived from global monthly ocean color averages which were assumed vertically homogenous. Climatology of LIDAR penetration depth was combined with the monthly mixed layer depth determined from the Global NCOM ocean circulation model. Global NCOM output was used to construct monthly averaged MLD climatologies from 2002 to 2010. Results show how monthly changes in MLD and LIDAR penetration depths are coupled for different regions of the global ocean. For example, the time-lag in LIDAR penetration depths is linked to shallowing of the MLD in the North Atlantic Bloom. We estimate the percentage of global ocean waters where different LIDAR system configurations can reach below the MLD. Results illustrate the potential performance of LIDAR systems to "probe" the subsurface for global waters which help in LIDAR design. Subsurface processes such as mixing and biological growth and decay have significant impact on what we observe at the ocean surface. LIDAR profiling should provide the new dimension for monitoring global ocean processes.