| The optical scattering characteristics of oceanic suspended particles can directly affect the transmitting property of laser in seawater, and they are also significant theory basement of oceanic environmental optics detecting. When a beam of light is emitted into seawater, elastic scattering and non-elastic scattering will occur due to the combined action of light and water. The frequency of elastic scattering light has no shift. While the scattering characteristics are depended on incident wavelength, attribute of seawater, size and density of suspended particles and so on. The main scattering elements which provoke elastic scattering in seawater are water molecules and suspended particles. Elastic scattering usually contains Rayleigh scattering, Mie scattering and non-selective scattering. Water molecules mainly provoke Rayleigh scattering, while suspended particles mainly provoke Mie scattering. People can get information about the dimension and density of suspended particles by doing research on Mie scattering characteristics of suspended particles. Another scattering activated by light and water is non-elastic scattering. The frequency of such scattering light has a shift. Non-elastic scattering is divided into two kinds: Raman scattering and Brillouin scattering. Raman scattering is related to molecule structure of substance, while Brillouin scattering is introduced duo to Doppler Effect. And Brillouin scattering is closely related to the temperature and salinity of seawater. After analyzing the Brillouin scattering characteristics, the temperature and salinity detecting model of oceanic suspended particles can be established.In ordinary occasion, water molecule in seawater is smaller than wavelength of light, and its scattering characteristics can be described by Reyleigh scattering theory. Suspended particles mainly contain phytoplankton and non-algal particles. The density, dimension and distribution of these particles are quite complex, and there are no strict theory to describe them. Nowadays, the technology of studying scattering characteristics of water molecules with Rayleigh theory is more and more mature. About the research of scattering coefficient of marine phytoplankton, people usually use empirical equation of chlorophyll density to calculate it. This method has a rather large error. It is difficult to analyze the characteristics of scattering coefficient by empirical equation either. The scattering coefficient of complex non-algal particles is also depended on empirical equation. They all have immature aspects. Meanwhile, the strict theory to describe the characteristics of back scattering power is not existed yet. This leads to the difficulty to calculate the concrete value of scattering power.Focusing on the problems above, making use of equivalent sphere Mie scattering theory, this paper analyzes the scattering characteristics of oceanic suspended particles. At first, it promotes a formula to calculate scattering coefficient of suspended particles using scattering efficiency factor. This solves the inaccuracy problems to calculate the scattering efficiency of phytoplankton and non-algal particles, and it can analyze the characteristics of scattering coefficient effectively. Then, the formulas of back scattering efficiency of phytoplankton and non-algal particles are deduced using scattering phase function. These can accurately calculate the back scattering efficiency of suspended particles, and analyze the characteristics of back scattering coefficient effectively.At present, the realization of detecting temperature of seawater using Brillouin scattering theory relies on the detecting of frequency drift of Brillouin scattering signal. During the process, the salinity of seawater is usually considered as a constant. This leads to a large measurement error, and at the same time, the salinity of seawater can't be detected. This paper bases on the research of Brillouin scattering characteristics of oceanic suspended particles, introduces a variable of Brillouin scattering energy, separately establishes detecting model of temperature and salinity of seawater using the frequency drift and energy parameters of Brillouin scattering signal, and finally realizes simultaneous measurement of temperature and salinity of seawater. The paper designs Brillouin scattering detecting system of lidar, simulates the absorption spectrum of I2127 in the range of wavelength between 470nm and 550nm, finds out appropriate absorption line, and completes the final design of frequency discriminator system. It analyses the proper monochromatic and stable frequency indexes that satisfy the detecting system's demand, and makes a proper choice of detecting laser.Based on airborne lidar technology, this paper simulates the detecting of oceanic suspended particles. Targeting the application of marine red tide, taking the detecting of density of red tide as foundation, and the detecting of temperature and salinity as accessory, the paper not only essentially solves the effect of suspend sand and water molecule to echo signal, but also more accurately and directly reflects correlated information of red tide with multi-parameter, which has higher forecast precision than one-parameter forecast method. It supplies necessary theory foundation and technical support for real detecting and predicting of marine red tide. Targeting the detecting application of suspended particles in entrance of the ocean, making use of the information that blue-green laser can penetrate turbid seawater to detect density of suspended particles; the paper provides a foundation to real suspended particles density detecting. According to the detecting of Mie scattering and Brillouin scattering characteristics of oceanic suspended particles, this paper supplies necessary theory foundation for realization of practice system, and holds wide environment, society and economy benefit foreground in oceanic red tide detecting, suspended particles detecting, cruise, forecast, emergency and track.
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