Study On Spectral Radiative Transfer Characteristics Of Rough Sea Surface Under Sea Fog Environment

The ocean,which is rich in fossil energy and biological resources,is an important guarantee for my country’s economic security,energy security and territorial security.In the process of developing and protecting the ocean,the radiation characteristics of rough sea surface is an important link in the research of atmosphere ocean radiation transmission process.Further deepening the research on its spectral reflection characteristics and the radiation transmission characteristics of sea fog particle system near the offshore surface is of great significance to the development of military and civil activities such as environmental monitoring,target recognition and information communication.In this thesis,rough sea surface,two-dimensional Gaussian random rough surface and sea fog rough sea surface coupling layer are studied.Based on thermal radiation transfer theory and electromagnetic scattering theory,Monte-Carlo method is used to study the reflection characteristics of rough sea surface in visible infrared band and microwave band,and the radiation transfer characteristics of sea fog rough sea surface coupling layer.At the same time,based on vector radiation transfer theory and the basic principle of polarization imaging,the effects of sea fog visibility,sea fog layer thickness and other factors on target polarization imaging are studied.The main work includes:(1)Based on the Elfouhaily spectrum,which describes the low-frequency part and highfrequency part of the wave in more detail,the linear filtering method is used to generate a twodimensional rough sea surface model under the conditions of different wind speeds and wind directions.Based on Cox-Munk rough sea surface slope distribution model,the reflection characteristics of rough sea surface such as spectral reflectance and bidirectional reflection distribution function are studied theoretically in visible infrared band and microwave band by Monte-Carlo method.Based on Elfouhaily spectral sea surface model,the effects of wind speed,incident angle and other factors on its radar cross section are explored.It is found that when the incident angle changes in the range of 0°-60°,the variation trend of spectral reflectance of rough sea surface is significantly different between visible-infrared band and microwave band.In addition,the changes of incident angle and wind speed also have a significant impact on the bidirectional reflection distribution function and radar cross section of rough sea surface.(2)Based on the two-dimensional Gaussian random rough surface model,combined with many kinds of common sea surface oil slicks,the effects of incident angle and root mean square slope on the hemispherical reflectivity of rough surface are systematically analyzed,which provides a theoretical reference for engineering applications involving the reflection characteristics of random rough surface such as sea surface oil slick monitoring.The research results show that the change of the root mean square slope will lead to changes in the number of incident light reflections and the occlusion rate of the first reflection point,which in turn affects the hemispherical reflectivity of the rough surface.In addition,the reflectivity corresponding to the normal incidence and oblique incidence cases has a large difference with the change trend of the rms slope.(3)Combined with Cox-Munk rough sea surface slope distribution model and khragian Mazin fog droplet particle size distribution model,the sea fog rough sea surface coupling calculation model is established.Based on Mie scattering theory,the spectral radiation characteristics of sea fog particle system in visible infrared band and microwave band are studied,and the influence of attenuation of sea fog particles near the sea surface on the spectral radiation transmission characteristics of sea fog rough sea surface coupling layer is evaluated by Monte Carlo method.It is found that the spectral radiation characteristics of sea fog particle system show complex changes under different visibility,and the multiple scattering between sea fog particles near the sea surface will significantly affect the spectral reflection characteristics of sea fog rough sea surface coupling layer.(4)Based on the vector radiation transfer theory and the basic principle of polarization imaging,combined with the Khragian-Mazin droplet particle size distribution model,the research on target polarization imaging in sea fog environment is carried out.The results show that,although the unit radiation intensity of the Q component imaging results of the target in different visibility sea fog environments is lower than the I component,the target background intensity of the Q component imaging results is much larger than the I component.The addition of polarization information effectively enhances the recognition ability of the detection target in the sea fog environment is improved.