Study On The Scattering Characteristics Of Ships On The Sea Surface To The Solar Bright Bands

When the sun shines on the wind-roughed sea surface,it will produce many glints.Each wave surface whose oriention will provide a specular solar reflection.The aggregation of numerous flash wave surfaces is called the solar bright band.Due to its strong polarization characteristics,the closer it is to the central region of the bright band,the stronger the polarization characteristics are.Therefore,when studying the light scattering characteristics of sea targets,the bright band of the sun cannot be ignored,and it also has significant application value for remote sensing of the atmosphere and the earth and the sea.In this thesis,the scattering characteristics of ships on the sea surface to the solar bright band are mainly studied.Because the reflection polarization characteristics of the solar bright band are affected by factors such as wind speed,solar incident zenith angle,solar-observation relative azimuth angle,etc.,the scattering characteristics of ships are analyzed by calculating the parallel polarization scattering component and vertical polarization scattering component under different parameters.The main contents of this thesis are summarized as follows:The rough sea surface under different wind speeds is simulated by Monte Carlo method combined with P-M sea spectrum model.The distribution of solar irradiance,sky background radiance and atmospheric path thermal radiation in different wave bands,different incident zenith angle and different observation angles are calculated by atmospheric transmission software MODTRAN.According to Fresnel reflection law,the polarization reflection of calm sea surface is obtained The probability density function of sea surface slope distribution is used to describe the wave distribution on the sea surface,and Fresnel reflection coefficient is used to describe the polarization radiation characteristics of mirror reflection of sea surface elements.The directional polarization reflectivity of rough sea surface is calculated by combining them.The distribution of vertical and parallel polarization reflectivity with observation angle under different wave bands,different solar incidence angles and different wind speeds is calculated.The polarization characteristics of seawater surface in visible and infrared bands are analyzed,and the polarization effects of atmosphere,sea surface roughness and water flare on total radiation of seawater surface are further explored in infrared band.Based on the polarization reflectivity of rough sea surface,the polarized reflection data of the solar bright band on the sea are obtained,which are determined by the geometric orientation of the sun incident,the geometric orientation of the observation direction,as well as the wind speed and other parameters.,and the distribution images of the bright solar band under different conditions are simulated Since the target model and the sea surface model are composed of a large number of small bins,firstly,the shading relationship between bins is judged by the geometric relationship between bins,and then the calculation method of polarization scattering of the bright solar band by the target bin is obtained according to the polarization reflection characteristics of the bright solar band on the sea surface and BRDF of the target surface.The ship model is combined with the established sea surface model,and the distribution of vertical and parallel scattering components of the ship to the bright band of the sea surface under different observation geometric orientations,different wind speeds and different wave bands is calculated by using the calculation method of target to solar bright band.Finally,the polarization scattering characteristics of the ship target to the bright band of the sun are compared and analyzed.