Suspended Matter, Ocean Optics, Coastal Remote-Sensing

What Drives the Coastal OceanRemote-Sensing Reflectance ?

Robert H. Stavn

Biology Dept., Univ. of North Carolina at Greensboro, Greensboro, NCNaval Research Lab., Oceanography Division, Stennis Space Center, MS

21. June 2012

Introduction

Two Major Issues Facing Remote-Sensing of Coastal & Inland Waters:

• The Major Optical Driver of In-Water Scattering/backscattering signal

• Atmospheric Correction and Bright/Dark Pixels in the Near IR

Suspended Mineral Matter is the key

Overall Requirements for Coastal Ocean Remote-Sensing

• Valid Ocean Optical Properties

• Portable (Robust) Remote-Sensing Algorithms

• Suspended Mineral Effects on Optical Scattering

• Aggregation of Mineral Colloidal/Nanoparticles

• Biogeo-optical Models and Biogeochemistry

Valid Ocean Optical Properites

m ijPIM i j

m m ijv

•True Optical Cross Sections, Mass-Specific Scattering Cross Section:

o ijPOM i j

do do o ijf v

• Working with known Particle Size Distributions and Refractive Indices

Portable Remote-Sensing Algorithms

Suspended Minerals Strongest Effect on Scattering/backscattering signal

Bio-optical Inversions do not work in Coastal Biogeo-optical Systems:

• Irish Sea: Binding, Bowers, McKee, Cunningham

• Canadian Lakes: Bukata, Jerome, Gallie, Murtha, et al.

Suspended Mineral Matter Violates Dark Pixel Assumption for Atmospheric Correction – Not Investigated Quantitatively

Dark Pixel Assumption and Mineral Scattering

Dark Pixel Assumption and Mineral Scattering

Note the Effect of Particle Size on single scattering albedo in near IR:

• 0.25 m Particles Scattering/backscattering nearly 1.0

• 0.5 – 0.7 m Particles Scattering/backscattering 0.6 – 0.8

Suspended Mineral Matter is the key & not yet investigated quantitatively

Suspended Mineral Effects on Optical Scattering

Aggregation of Mineral Colloidal/Nano Particles

Colloidal/Nano Particles Aggregate Spontaneously and Significantly Affect the PSD:

Aggregation of Mineral Colloidal/Nano Particles

Particles Larger than 1 m tend to aggregate from Brownian (DLA) and Shear (RLA) Collisions:

Aggregation of Mineral Colloidal/Nano Particles

Two Major Mechanisms:

• DLA – Diffusion Limited from Brownian Motion

• RLA – Reaction Limited from Hydrodynamic Shear

Aggregation of Mineral Colloidal/Nano Particles

Structure of Aggregate Particles Described by Fractal Geometry:

• DLA Structures have low Fractal Dimension: 1.5 – 2.5

• RLA Structures have high Fractal Dimension: 2.5 – 3.0

Aggregation of Mineral Colloidal/Nano Particles: PSD

Primary Particle Dominated PSD (Risovic Gamma Formulation):

Aggregation of Mineral Colloidal/Nano Particles: PSDAggregated Particle Dominant PSD (Risovic Gamma Formulation):

Aggregation of Mineral Colloidal/Nano Particles: Optics

Optical Effects of Primary Particle Dominant PSD:

Spectral Mass-specificScattering Cross Sections

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Wavelength (nm)

[PI

M] (

) (m2 /g

)

Mobile BayIllite LowIllite StdIllite HighMont. LowMont. StdMont. High

Aggregation of Mineral Colloidal/Nano Particles: Optics

Optical Effects of Aggregate Particle Dominant PSD:

Spectral Mass-specificScattering Cross Sections

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Wavelength (nm)

[PI

M] (

) (m2 /g

)

Irish Sea M. & C.Irish Sea BowersIllite LowIllite StdIllite HighMont. LowMont. StdMont. High

Biogeo-optics & Biogeochemistry

Ecosystem Stoichiometry: O(212):C(108):N(16):P(1)Redfield Ratio

Redox Reactions: Electron Flow Photosynthesis/Respiration

Sorption & Chelation critical nutrients, trace elements,pollutants

Limiting NutrientsFreshwaters: Phosphate

PO4 sorption on suspended clay minerals

Coastal Ocean: NitratePO4 desorption from suspended clayminerals

Sorption: function of clay surface area, i.e.Particle Size Distribution & aggregation

Mouth of Mississippi: Clay Minerals, Quartz, & Amorphous Silica (Diatoms)

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6.8

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16.4

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35.6

13b-0.1274

14b-0.1238

15b-0.1274

13b-0.1274triple dwelltime14b-0.1238-triple dwelltime