Relationship between spectral particulate attenuation and particle size distribution
description
Transcript of Relationship between spectral particulate attenuation and particle size distribution
![Page 1: Relationship between spectral particulate attenuation and particle size distribution](https://reader035.fdocuments.us/reader035/viewer/2022062314/56814449550346895db0e6fa/html5/thumbnails/1.jpg)
Relationship between spectral particulate attenuation and
particle size distribution
Peng Wang
![Page 2: Relationship between spectral particulate attenuation and particle size distribution](https://reader035.fdocuments.us/reader035/viewer/2022062314/56814449550346895db0e6fa/html5/thumbnails/2.jpg)
Introduction:
• Particle Size Distribution (PSD):
Information about the ecological dynamics of marine water, particulate sedimentation fluxes and sediment transport;
• Beam attenuation coefficient (C):
Quantify light propagation in the ocean and to study the concentration of the material affecting light propagation.
![Page 3: Relationship between spectral particulate attenuation and particle size distribution](https://reader035.fdocuments.us/reader035/viewer/2022062314/56814449550346895db0e6fa/html5/thumbnails/3.jpg)
PSDs could be well approximated by a hyperbolic (Junge-like) distribution :
N(D) = N0(D/D0)-ξ
• N(D): the number of particles with diameters between D and D+dD divided by dD;
• D0: reference diameter;
• ξ: PSD slope varying between 3 and 5.
![Page 4: Relationship between spectral particulate attenuation and particle size distribution](https://reader035.fdocuments.us/reader035/viewer/2022062314/56814449550346895db0e6fa/html5/thumbnails/4.jpg)
The particulate attenuation cp:cp(λ) = cp(λ0) λ-γ
The exponent of the particulate attenuation spectrum (γ) and the exponent of the PSD (ξ) are linearly by
γ = ξ – 3
([Diehl and Haardt, 1980]);
The main goal of this study is to test that relationship.
![Page 5: Relationship between spectral particulate attenuation and particle size distribution](https://reader035.fdocuments.us/reader035/viewer/2022062314/56814449550346895db0e6fa/html5/thumbnails/5.jpg)
Methods: Cp
Cp = Cpg – Cg
![Page 6: Relationship between spectral particulate attenuation and particle size distribution](https://reader035.fdocuments.us/reader035/viewer/2022062314/56814449550346895db0e6fa/html5/thumbnails/6.jpg)
PSDs: Coulter Counter
3-10 um range used: avoid noise in the small size range (2<D<3um); the scarcity of particles >10 um made statistical very bad.
![Page 7: Relationship between spectral particulate attenuation and particle size distribution](https://reader035.fdocuments.us/reader035/viewer/2022062314/56814449550346895db0e6fa/html5/thumbnails/7.jpg)
Results:
1. Optical Data:
Cruise:CD
Cruise:AB
![Page 8: Relationship between spectral particulate attenuation and particle size distribution](https://reader035.fdocuments.us/reader035/viewer/2022062314/56814449550346895db0e6fa/html5/thumbnails/8.jpg)
Super mixed water !!!
![Page 9: Relationship between spectral particulate attenuation and particle size distribution](https://reader035.fdocuments.us/reader035/viewer/2022062314/56814449550346895db0e6fa/html5/thumbnails/9.jpg)
Fitted Cp Curves:
![Page 10: Relationship between spectral particulate attenuation and particle size distribution](https://reader035.fdocuments.us/reader035/viewer/2022062314/56814449550346895db0e6fa/html5/thumbnails/10.jpg)
Fitted PSDs Curves:
![Page 11: Relationship between spectral particulate attenuation and particle size distribution](https://reader035.fdocuments.us/reader035/viewer/2022062314/56814449550346895db0e6fa/html5/thumbnails/11.jpg)
Comparison: ξ for Two Different Particle Size
Ranges and Spectral Slope γ Cp(440) ξ for
2<D<10umξ for
3<D<10umγ
AB surf 0.6575 7.8273 3.4445 0.4861
AB 10m 0.6575 9.8067 3.2151 0.484
CD stn1 3.7436 3.32 3.5679 0.608
CD stn2 surf 4.098 2.9453 3.7722 0.6998
CD stn2 10m 4.098 2.8565 3.4784 0.6998
![Page 12: Relationship between spectral particulate attenuation and particle size distribution](https://reader035.fdocuments.us/reader035/viewer/2022062314/56814449550346895db0e6fa/html5/thumbnails/12.jpg)
Theoretical and measured relationship:
3.1
3.2
3.3
3.4
3.5
3.6
3.7
3.8
3.9
0.4 0.5 0.6 0.7 0.8
Spectra Slope of Cp
Slo
pe
of
PS
D
measured relation
theorical relation
![Page 13: Relationship between spectral particulate attenuation and particle size distribution](https://reader035.fdocuments.us/reader035/viewer/2022062314/56814449550346895db0e6fa/html5/thumbnails/13.jpg)
• The shapes of the particulate attenuation spectra (cp(λ)) were found to be well approximated by a power law with respect to wavelength;
• A single Junge exponent was found not to match very well the whole data from 2 to 10 um; a better fit was found when the size range was limited to 3 < D < 10 um;
• The range of observed values of ξ and γ is relatively consistent with the linear relationship: γ = ξ – 3 .
Conclusions: