Suppression of local haze variations in MERIS images over turbid coastal waters for retrieval of suspended sediment concentration

Fang Shen,Wouter Verhoef

doi:10.1364/oe.18.012653

Abstract

Atmospheric correction over turbid waters can be problematic if atmospheric haze is spatially variable. In this case the retrieval of water quality is hampered by the fact that haze variations could be partly mistaken for variations in suspended sediment concentration (SSC). In this study we propose the suppression of local haze variations while leaving sediment variations intact. This is accomplished by a multispectral data projection (MDP) method based on a linear spectral mixing model, and applied prior to the actual standard atmospheric correction. In this linear model, the hazesediment spectral mixing was simulated by a coupled water-atmosphere radiative transfer (RT) model. As a result, local haze variations were largely suppressed and transformed into an approximately homogenous atmosphere over the MERIS top-of-atmosphere (TOA) radiance scene. The suppression of local haze variations increases the number of satellite images that are still suitable for standard atmospheric correction processing and subsequent water quality analysis.

Highlights

For ocean colour and water quality mapping one needs atmospherically clear satellite scenes, but these are seldom available
Terrestrial suspended particulate matters or resuspension from the bottom in shallow waters carried by river plume to the ocean, along with amounts of nutrients and pollutant materials, can impact oceanic environments, for instance, in the Changjiang (Yangtze River) Estuary and Coast
Regarding correction of spatially varying haze, an extension of the image-based dark object subtraction method proposed by [6] is to partition a scene into sub-regions which are treated individually, the Tasseled-Cap Transforms [7], where the haze component (TC4) is applied pixel-by-pixel to estimate the radiometric contribution from haze, and correction of haze is made by subtracting the amount of additive shift for each pixel, or by histogram matching

Summary

Introduction

For ocean colour and water quality mapping one needs atmospherically clear satellite scenes, but these are seldom available. Terrestrial suspended particulate matters or resuspension from the bottom in shallow waters carried by river plume to the ocean, along with amounts of nutrients and pollutant materials, can impact oceanic environments, for instance, in the Changjiang (Yangtze River) Estuary and Coast. Such matters consist mainly of suspended finest-grain sediment particles with an average diameter of 8.6 μm [5], hereafter referred as “sediment”. The Haze Optimized Transform (HOT) reported by [3] is to detect haze and its effect in conjunction with a “dark target” subtraction methodology to radiometrically adjust visible-band imagery These methods were applied to land scenes

Methods

Results

Conclusion