Two Major Issues Facing Remote-Sensing of Coastal & Inland Waters: • The
Major Optical Driver of In-Water Scattering/backscattering signal. • Atmospheric ...
Suspended Matter, Ocean Optics, Coastal Remote-Sensing What Drives the Coastal Ocean Remote-Sensing Reflectance ?
Robert H. Stavn Biology Dept., Univ. of North Carolina at Greensboro, Greensboro, NC Naval 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 •True Optical Cross Sections, Mass-Specific Scattering Cross Section:
m ij PIM i j mvm ij o ij POM i j dofdovo ij • 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: PSD Aggregated Particle Dominant PSD (Risovic Gamma Formulation):
Aggregation of Mineral Colloidal/Nano Particles: Optics Optical Effects of Primary Particle Dominant PSD: Spectral Mass-specific Scattering Cross Sections 1.10 1.00 0.90
[PIM]() (m2/g)
0.80 0.70 0.60 0.50
Mobile Bay Illite Low Illite Std Illite High Mont. Low Mont. Std Mont. High
0.40 0.30 0.20 0.10 0.00 350
400
450
500
550
600
650
Wavelength (nm)
700
750
Aggregation of Mineral Colloidal/Nano Particles: Optics Optical Effects of Aggregate Particle Dominant PSD: Spectral Mass-specific Scattering Cross Sections 1.10 Irish Sea M. & C. Irish Sea Bowers Illite Low
1.00 0.90
Illite Std Illite High Mont. Low Mont. Std Mont. High
[PIM]() (m2/g)
0.80 0.70 0.60 0.50 0.40 0.30 0.20 0.10 0.00 350
400
450
500
550
600
Wavelength (nm)
650
700
750
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 Nutrients Freshwaters: Phosphate PO4 sorption on suspended clay minerals Coastal Ocean: Nitrate PO4 desorption from suspended clay minerals Sorption: function of clay surface area, i.e. Particle Size Distribution & aggregation
Mouth of Mississippi: Clay Minerals, Quartz, & Amorphous Silica (Diatoms) 120
13b-0.1274
100 14b-0.1238 80 15b-0.1274
60 40 20
35.6
30.8
26
21.2
16.4
11.6
6.8
2
0
13b-0.1274 triple dwell time 14b-0.1238triple dwell time
