Transmission across the water-air interface: resolving the impact of multiple interactions at the sea surface.

David Mckee,Jacek Piskozub

doi:10.1364/oe.414085

Abstract

A series of Monte Carlo and HydroLight radiative transfer simulations are used to demonstrate that the traditional form of the Fresnel transmission across the water-air interface is accurate. This contradicts assertions to the contrary in a recent paper [Opt. Express25, 27086 (2017)10.1364/OE.25.027086] that suggested that the impact of multiple surface interactions had previously been ignored and that the transmission factor was dependent upon the turbidity of the water.

Highlights

Transmission of light from below the sea surface into air is a key process in the formation of ocean colour remote sensing signals
Such a dramatic assertion on such a fundamental point of radiative transfer simulation attracted interest and within a short period a response to the original article was published by Gordon and Voss (G&V) that challenged the theoretical basis of the proposed new model for water-air transmission [2]
Because the beam half-width in water was identical to the radiance collection angle (7°), the total subsurface radiance signal, Lu(λ,0−), is the sum of photons reaching the interface during the initial and subsequent interactions at the sea surface, Lux(λ,0−)

Summary

Introduction

Transmission of light from below the sea surface into air is a key process in the formation of ocean colour remote sensing signals. Dev and Shanmugam (D&S) [1] presented a new analysis of this process that challenges the established order and suggested that previous analyses had missed (i) a particulate contribution to the refractive index (RI) of seawater and (ii) multiple interactions of the upwelling photons with the water-air interface. The net effect of these alleged omissions was that the community had systematically underestimated water leaving radiances by as much as 33% in highly scattering waters. Such a dramatic assertion on such a fundamental point of radiative transfer simulation attracted interest and within a short period a response to the original article was published by Gordon and Voss (G&V) that challenged the theoretical basis of the proposed new model for water-air transmission [2]. The suggestion that particulate refractive index influenced the water-air transition was challenged

Methods

Results

Discussion

Conclusion