Three-Dimensional Mapping of Fluorescent Dye Using a Scanning, Depth-Resolving Airborne Lidar

Abstract

Results are presented from a pilot study using a fluorescent dye tracer imaged by airborne lidar in the ocean surface layer on spatial scales of meters to kilometers and temporal scales of minutes to hours. The lidar used here employs a scanning, frequency-doubled Nd:YAG laser to emit an infrared (1064 nm) and green (532 nm) pulse 6 ns in duration at a rate of 1 kHz. The received signal is split to infrared, green, and fluorescent (nominally 580-600 nm) channels, the latter two of which are used to compute absolute dye concentration as a function of depth and horizontal position. Comparison of dye concentrations inferred from the lidar with in situ fluorometry measurements made by ship shows good agreement both qualitatively and quantitatively for absolute dye concentrations ranging from 1 to Ͼ10 ppb. Uncertainties associated with horizontal variations in the natural seawater attenuation are approximately 1 ppb. The results demonstrate the ability of airborne lidar to capture high-resolution three-dimensional "snapshots" of the distribution of the tracer as it evolves over very short time and space scales. Such measurements offer a powerful observational tool for studies of transport and mixing on these scales.

Chaotic advection in a steady, three-dimensional, Ekman-driven eddy

“…Although the images lack the clarity and resolution of Poincaré sections or pinpoint dye release, they apparently have the potential to reveal the most prominent Lagrangian structures. This result also provides hope that some barriers may be detectable in the field using tracer release experiments (Sundermeyer et al 2007).…”

Observations and numerical simulations of large‐eddy circulation in the ocean surface mixed layer

“…An inversion algorithm to convert the lidar returns to absolute dye concentration was applied to the 2004 data and is reported by Sundermeyer et al [2007]. A second generation inversion routine for the 2011 data is in preparation.…”

Long-distance fluorescence lifetime imaging using stimulated emission

“…This can be of use in image-guided surgery 34 or airborne (or perhaps ultimately satellite) biological and environmental monitoring. 35 Our future work will hence focus on extending the detected lifetime range to significantly shorter fluorescence lifetimes, a domain in which the use of ultrafast pulsed lasers and pumpprobe type techniques has the greatest benefits over other methods, as well as on expanding the applied prospects of LDFLI.…”