Observations from an Airborne Two-Wavelength Ocean Profiling High Spectral Resolution Lidar in the Atlantic and Pacific Oceans and South China Sea

We present first-ever observations from a two-wavelength ocean profiling high-spectral-resolution lidar (HSRL). These data were acquired with the recently upgraded airborne HSRL-2 instrument in flights over the Atlantic Ocean off the East Coast of the US, transit flights across the Pacific from the US to the Philippines, and flights conducted from the Philippines over the West Pacific, South China Sea, and Sulu Sea. HSRL-2 is NASA Langley Research Center’s (LaRC’s) second-generation airborne HSRL and was developed initially as an aerosol-cloud lidar for deployment on science-focused airborne field experiments and as a prototype for an advanced spaceborne lidar. Based on the success of LaRC’s first-generation airborne HSRL in ocean profiling at 532 nm, NASA’s Earth Science Technology Office funded modifications of the HSRL-2 instrument to enable ocean profiling at both 355 and 532 nm. These modifications were completed in early 2019, and HSRL-2 now provides independent, depth-resolved measurements of diffuse attenuation coefficient and particulate backscatter at both 355 and 532 nm. The goal for measuring attenuation at the two wavelengths is to resolve absorption into components due to plankton pigments and colored dissolved organic matter. Backscatter measurements at the two wavelengths are to provide information on the slope of the size distribution of particles in addition to the vertical distribution of biomass. In addition, the lidar resolves the backscatter into components polarized parallel and perpendicular to the transmitted pulse. The data products can be combined to provide a variety of vertically and horizontally resolved intensive observables that depend on the type of particles/plankton rather than their concentration (e.g., the ratio of particulate backscatter to attenuation or depolarization to attenuation). The instrument also measures chlorophyll and CDOM fluorescence. HSRL-2’s modifications retained all of the instrument’s original aerosol and cloud capabilities, making this lidar particularly applicable to assessment of aerosol correction in passive ocean color retrievals as well as coupled ocean-atmosphere studies. This presentation will focus on initial results from recent flights and discuss the potential for similar capability from a polar-orbiting spaceborne lidar.