Efficient single-scattering lookup table for lidar and polarimeter phytoplankton studies

Optics Letters, vol. 49, pp. 2453

Abstract

Coupled atmosphere and ocean remote sensing retrievals of aerosol, cloud, and oceanic phytoplankton microphysical properties, such as those carried out by the NASA Plankton, Aerosol, Cloud, ocean Ecosystem (PACE) mission, involve single-scattering calculations that are time consuming. Lookup tables (LUTs) exist to speed up these calculations for aerosol and water droplets in the atmosphere. In our new Lorenz–Mie lookup table, we tabulate single scattering by an ensemble of coated isotropic spheres representing oceanic phytoplankton at wavelengths from 0.355 µm. The lookup table covers phytoplankton particles with radii in the range of 0.15–100 µm at an increase of up to 104 in computational speed compared to single-scattering calculations. The allowed complex refractive indices range from 1.05 to 1.24 for the shell’s real part, from 10-7 to 0.3 for the shell’s imaginary part, from 0 to 0.001 for the core’s imaginary part, and equal to 1.02 for the core’s real part. We show that we precisely compute inherent optical properties for the phytoplankton size distributions ranging up to 5 µm for the effective radius and up to 0.6 for the effective variance. We test wavelengths from 0.355 to 1.065 µm and find that all the inherent optical properties of interest agree with the single-scattering calculations to within 1% for 99.9% of cases. We also provide an example of using the lookup table to reproduce the phytoplankton optical datasets listed in the PANGAEA database for synthetic hyperspectral algorithm development. The table together with C++, Fortran, MATLAB, and Python codes to apply different complex refractive indices and phytoplankton size distributions is freely available online.

Authors 9

1. Eduard Chemyakin

   Langley Research Center

   Affiliation as printed

   NASA Langley Research Center (LaRC)

2. Snorre Stamnes

   Langley Research Center

   Affiliation as printed

   NASA Langley Research Center (LaRC)

3. James Paul Allen

   Goddard Space Flight Center · Morgan State University

   Affiliation as printed

   Goddard Earth Sciences Technology and Research (GESTAR) II/Morgan State University

   NASA Goddard Space Flight Center (GSFC)

4. S. P. Burton

   Langley Research Center

   Affiliation as printed

   NASA Langley Research Center (LaRC)

5. Johnathan W. Hair

   Langley Research Center

   Affiliation as printed

   NASA Langley Research Center (LaRC)

6. C. A. Hostetler

   Langley Research Center

   Affiliation as printed

   NASA Langley Research Center (LaRC)

7. Jacek Chowdhary

   Goddard Institute for Space Studies · Columbia University

   Affiliation as printed

   Columbia University

   NASA Goddard Institute for Space Studies (GISS)

8. Bastiaan van Diedenhoven Aachen SRON Netherlands Institute for Space Research

   Space Research Organisation Netherlands

   Affiliation as printed

   SRON Netherlands Institute for Space Research

9. Brian Cairns

   Goddard Institute for Space Studies

   Affiliation as printed

   NASA Goddard Institute for Space Studies (GISS)