suspended matter, ocean optics, coastal remote-sensing · introduction two major issues facing...
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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
0.00
0.10
0.20
0.30
0.40
0.50
0.60
0.70
0.80
0.90
1.00
1.10
350 400 450 500 550 600 650 700 750
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
0.00
0.10
0.20
0.30
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0.50
0.60
0.70
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0.90
1.00
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350 400 450 500 550 600 650 700 750
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)
0
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1202
6.8
11.6
16.4
21.2 26
30.8
35.6
13b-0.1274
14b-0.1238
15b-0.1274
13b-0.1274triple dwelltime14b-0.1238-triple dwelltime