Scale invariance rule look-up table for lidar and polarimeter retrievals

There is an increasing interest in combining simultaneous measurements with active and passive remote sensing instruments to obtain the properties of ambient aerosol in a vertically resolved manner. For instance, the combination of lidar and polarimeter simultaneous observations is expected to reduce uncertainties in the retrievals of aerosol radiative forcing. The calculations of single-scattering properties in the lidar and polarimeter aerosol microphysical retrievals are time consuming. The common way to speed up these calculations is to use a look-up table. The most efficient look-up table that is currently in use was created about a decade ago [1]. The modern computers allow us to create a new look-up table that inherits the previously developed mathematical approach but has a superior precision over an extended range of aerosol sizes. In our first in a line of improved look-up tables, we tabulate the light scattering by an ensemble of homogeneous spheres at wavelengths starting from 0.355 to at least 2.264 m. The improved look-up table allows us to cover the ambient spherical particles with a radius range of 0.001100 m, with the complex refractive index in a range of 1.291.65 for the real part and in a range of 00.05 for the imaginary part. The comparisons to simulated truth at twelve wavelengths in a range of 0.3552.264 m demonstrated that the elements of the normalized scattering matrix as well as the asymmetry parameter, the aerosol absorption, backscatter, extinction, and scattering coefficients are precise to within 1% for 99.99% of cases [2]. We target the 1% precision to reduce forward model errors in modeling state-of-the-art lidar and polarimeters (Aerosol, Cloud, Convection and Precipitation study), as well as in microphysical retrievals for the next generation of satellite sensors (Architecture D1A instruments). The look-up table along with examples of its use are freely available at https://science.larc.nasa.gov/polarimetry. [1] Dubovik, O. et al, 2006: Application of Spheroid Models to Account for Aerosol Particle Nonsphericity in Remote Sensing of Desert Dust. J. Geophys. Res. 111, D11208. doi:10.1029/2005jd006619. [2] Chemyakin, E. et al, 2021: Improved Lorenz-Mie Look-Up Table for Lidar and Polarimeter Retrievals. Front. Remote Sens. 2:711106. doi: 10.3389/frsen.2021.711106.