Research On Skylight Polarization Properties And Sensitive Spectrum Under Complex Atmosphere

By the scattering of gas, aerosol and cloud in atmosphere, the skylight forms a regular polarization pattern. Many insects can identify the direction by apperceiving the polarization information of the skylight, which inspired the human navigation. In order to improve and use the polarized light navigation system better, it is very important to study the skylight polarization pattern under the actual atmosphere and biological polarization sensitive mechanisms.Using the vector radiation transfer model based on Monte Carlo method, the impact of complex atmospheric composition on skylight polarization properties is simulated, and the selection principle of insects’polarization sensitive spectrum is analyzed.Firstly, the simulation model of skylight polarization under complex atmosphere is built. The skylight polarization properties under different gas, aerosol and cloud models from350nm to700nm are simulated and analyzed. The results show that, atmospheric gas models have little impact on skylight polarization properties. The degree of polarization (DOP) decreases with the growth of the aerosol complexity, and the maximum DOP under continental, desert and maritime aerosols appears in red, violet and blue-green wavelength range separately. The DOP decreases with the increasing of cloud optical thickness and a little with the decreasing of cloud effective radius.Secondly, the full-sky DOP and angle of polarization (AOP) pattern of different solar altitude angles under clear and cloudy sky are simulated, and compared with the Rayleigh model. The result shows that, with the increasing of the solar altitude angle, the DOP of whole sky decreases. The extremely low DOP makes the AOP imprecise.Thirdly, the polarization patterns under different atmospheric models of ultraviolet, blue, green, red wavelength range are built. Combining the research of polarization properties under complex atmosphere, the selection principle of insects’polarization sensitive spectrum is explained. It supposes that in non-desert continental and maritime area, the cloudy condition makes the DOP and the detectable region of short wavelength larger than that of the long wavelength, which is the main factor of spectral selection. In desert area, desert aerosol greatly descends the DOP and the polarization detectable region of long wavelength and makes great impact on insects’ spectral selection. In summary, in order to improve the overall detection performance, short wavelength is more suitable for the polarization navigation under complex atmosphere.