The Study Of The Snow Reflection Model

Considering the background of global warming and high surface reflection of snow, any subtle changes of the reflection values would affect the global climate.Based on these reasons, it's highly urgent to build a model which can calculate the value of snow reflectance accurately and efficiently. In the process of building the model, researches are conducted from the following three parts:1. Calculate the optical properties of pure snow and snow which contain black or brown carbon aerosols with Mie scattering theory. Then compare the difference in phase function, extinction coefficient and single scattering reflection of the cases,respectively. It is found that snow with impurities have minor effects on extinction coefficient and phase function. However, the effect on single scattering reflection is comparatively obvious since the single scattering reflection increase with the concentration of impurities and the snow effective radius re. In addition, black carbon has greater effect on the reflection than brown carbon does. What's more, a modified DHG (Double Henyey-Greenstein) scheme is proposed in this study to improve the phase function parameterization. The modified scheme is stable, and the traits of forward scattering and backscattering are well characterized.2. Compare the reflectivity results of two and four-stream discrete ordinate expansion approximation schemes and the advanced four-stream radiation scheme is applied to compare the reflection of the pure snow and snow with impurities, then study the differences of the RGB color model results. It is shown that the effect of black carbon on the pure snow reflection is more obvious than brown carbon. In RGB model, it is found that snow with black carbon looks more blackish.3.The perturbation theory is applied to the model of snow reflection, we use two-stream spherical harmonic expansion approximation to quantify the asymmetric factor and single scattering reflection which are caused by impurities and consider these optical properties as perturbation in pure snow. Result shows,there's positive disturbance on asymmetric factor?g, and negative disturbance on single scattering reflection ?? and snow reflection. Black carbon always has a greater value in disturbance which become large rwith the growth of concentration and the effective radius of snow re...