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Mie scattering properties of marine particulates and Brillouin Scattering

Author: LinHong
Tutor: DongTianLin；MaYong
School: Huazhong University of Science and Technology
Course: Electromagnetic Field and Microwave Technology
Keywords: Ocean Optics Mie scattering Brillouin Scattering Suspended particulates Airborne Lidar
CLC: P733.3
Type: PhD thesis
Year: 2007
Downloads: 512
Quote: 7
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Abstract

The optical scattering properties of marine particulates not only directly affect the laser transmission characteristics in seawater, and optical monitoring of the marine environment is an important theoretical basis. When a beam of light is launched into the sea, through the interaction of light and water will occur elastic scattering and inelastic scattering. Elastic scattering of light does not shift in the frequency change, but the wavelength of the incident light scattering properties, the properties of water and suspended in seawater size, density and so on. Raised in seawater elastic scattering of light scattering million was primarily a saltwater ocean water molecules and suspended particulates. Including elastic scattering Rayleigh scattering, Mie scattering and non-selective scattering three categories, including water molecules in seawater is mainly caused by Rayleigh scattering, and is the main cause of marine particulates Mie scattering. Through the study of marine suspended Mie scattering, can be suspended in water in a variety of size, density and other information. Light and water produced by another inelastic scattering scattering, scattering the presence of such frequency of the scattered light of the frequency of the incident light moves. Inelastic scattering is divided into two categories: Raman scattering and Brillouin scattering. Raman scattering and the molecular structure of matter, whereas the Brillouin scattering is actually caused by the Doppler effect, it and the seawater temperature and salinity are closely related. By analyzing marine particulates Brillouin scattering properties of marine particulates can build water temperature and salinity detection model. Typically, the water molecules in water is much smaller than the wavelength of light, Rayleigh scattering theory can be used to describe the scattering characteristics; while marine phytoplankton particulates include particulates and non-pigmented two categories, the particle density, the size , distribution is extremely complex, there is no strict theoretical description. Currently, the use of Rayleigh scattering theory scattering properties of water molecules is relatively mature, and for marine phytoplankton scattering coefficient studies more chlorophyll concentration based on an empirical formula to calculate the size of the scattering coefficient, with some not accuracy, through empirical formula is difficult to analyze the scattering coefficient characteristics; against marine complex non-pigmented particulates, also rely mainly on empirical formulas to calculate the scattering coefficient, there are still a lot of immature place. Meanwhile, the description of phytoplankton in seawater and other marine and non-pigment suspended particulates rate characteristic backscatter rigorous theory does not yet exist, so then the specific values ??of the scattering rate has been difficult to calculate. In this paper, these issues focus using the equivalent sphere Mie scattering theory analysis of the scattering properties of marine particulates, first proposed the use of factors to calculate the scattering efficiency particulate scattering coefficient marine formula to solve the non-pigmented phytoplankton and suspended particulates other marine particulate scattering coefficient calculation is not accurate, but also can effectively analyze the scattering coefficient characteristics. Then, proposed to calculate the scattering phase function, phytoplankton and other marine suspended particulate pigmented backward scattering ratio formulas, can accurately calculate the sea backscatter rate of particulate size, but also can be effectively analyzed backscatter rate characteristics. Currently, the use of Brillouin scattering is detected by detecting the sea water temperature in the Brillouin frequency shift amount scattered signal to achieve, in this process, which is usually assumed constant salinity values, so there is a big measurement error, but is not able to measure ocean salinity information. Based on the analysis of Brillouin scattering sea suspended on the basis of the introduction of the Brillouin scattering power of this variable, the use of Brillouin scattering power of the frequency shift amount and two parameters were established and salt water temperature degree detection theoretical models, to achieve the detection of seawater temperature and salinity. By Brillouin scattering lidar detection system for 470nm to 550nm spectral region 127 within the molecular iodine absorption filter absorption lines of the simulation, and in this context to find suitable absorption lines, to complete the entire frequency discriminator detection system design, analysis, detection needs to meet single laser frequency stabilization targets, on this basis, select the appropriate probe laser. In combination with airborne laser radar technology, applied to the study of marine TSP Monitoring simulation analysis. For marine red tide monitoring applications, the article in order to detect red tide density information as the basis for detection of red tide water temperature, salinity, two parameters for the secondary, not only from nature to solve the suspended sediment and water molecules influence the echo signal , and the use of multiple parameters more accurately and directly reflects the tide ebb and flow information, than the single parameter prediction method has higher prediction accuracy for the actual red tide monitoring and forecasting to provide theoretical support and technical guidance. For estuaries suspended sediment particles detection applications, the use of blue-green laser can penetrate article muddy waters, effectively detect marine suspended sediment particles density information, the actual concentration of suspended sediment particles estuary provides guidance on testing. Marine particulates by Mie scattering characteristics and Brillouin scattering study of the actual realization of marine environmental monitoring provides the necessary theoretical support in the ocean tide, the estuary sediment and other marine environmental monitoring cruise, forecasting, emergency and tracking surveillance has broad environmental, social and economic prospects.

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CLC: > Astronomy,Earth Sciences > Oceanography > Marine basic science > Marine physics > Ocean Optics
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