Measurement of ocean water optical properties and seafloor reflectance with Scanning Hydrographic Operational Airborne Lidar Survey (SHOALS): Ⅰ. Theoretical Background

摘要

In earlier work, we have proposed a concept for estimation of ocean optical properties with a multiple field-of-view bathymetric lidar. In this paper, we consider an implementation of this idea using SHOALS. The SHOALS design uses two receivers for depth measurement: a shallow-water, APD receiver with an 18 mrad FOV; and a deep-water PMT receiver with a 40 mrad FOV. They simultaneously record the optical power returned from a single pulse of the laser, and consequently provide the desired measurements. Here, we present an algorithm for the estimation of inherent optical properties (IOPs) in the upper ocean layer which is based on "multiple-forward-single-backscattering" model of the returned power, and an analytical solution to the radiative transfer equation (RTE) for finite sounding beam propagation in the small-angle-scattering approximation. Using this algorithm, we have developed an approach for estimation of the backscattering coefficient, the beam attenuation coefficient, the single-scattering albedo, and the VSF asymmetry coefficient, by fitting simulated waveforms to actual data measured by the two receivers. We also present an approach for improvement in estimates of bottom reflectance which compensates for pulse stretching induced by angle of incidence effects.