A Simple Limb Model For Solving Vector Radiative Transfer In The Horizontal Inhomogeneous Atmosphere

The limb/occultation detection is an important way and direction for the satellite remote sensing. The inversion methods about the limb observation way could get a fine vertical distribution about the atmospheric elements. The most of the limb radiative transfer model that have existed currently are One-dimensional model based on the horizontal homogeneous distribution. And they also ignore the impact of atmospheric polarization. The polarization is an important means for the atmospheric remote sensing, especially for the limb detection in the UV band. In order to meet the demands of limb detection in the future, we developed a limb model for solving vector radiative transfer in the horizontal inhomogeneous atmosphere based on successive order of scattering. Then we made some comparison about the simulating value of the radiation intensity between ours model and the LGLTRAN model to prove the accuracy of this model. And we also made some simulation and simple analysis for the limb Stokes vector. The work includes:1. The model’s algorithm is introduced. The core algorithm of this model is successive order of scattering method and only the single scattering contribution has been considered in this model. We use the quadratic fit method to calculate the integration in the optical path to simplify the calculation.2. The overall framework of this model as well as the method of parameter handling is described. the model’s calculation order can be divided into: determining the observation path, calculating the optical parameters in each node on the observation path, calculating the source function in each node on the observation path, integrating in the optical path and using the successive order of scattering method calculate the vector radiation. Then we introduce the solving method about he optical parameters and the geometric parameters. In this model we consider the impact of the horizontal inhomogeneous distribution with spherical surface stratification, and use the three-dimensional linear interpolation method to calculate the optical parameters and so on in each node on the observation path.3. there are little limb vector radiative transfer model currently. In order to prove the accuracy of this model, we compare the simulating value of the radiation intensity between ours model and the LGLTRAN model in the condition of exactly same environmental parameters. The simulation results of this two models have good consistency and the deviations is small. The accuracy of model could be affirmed.Secondly, we compare the simulation results of radiation intensity from the two model at the UV wavelength300nm、340nm、355nm. The results show that Ours model and the LGLTRAN model have a consistent distribution characteristics. Firstly the radiation intensity increases exponentially with the tangential point height’s lower. Then when the tangential point height reaches a certain height, the radiation intensity increases slowly with the tangential point height’s lower.Finally, we simulate the vertical distribution of limb vector radiation under the different Atmospheric stratification. The simulation results were almost the same under different atmospheric stratification when the atmospheric stratification is large enough. And the effect of atmospheric stratification for the simulation accuracy can be ignored. Furthermore, the atmospheric stratification serious impact the calculation time.4. In order to verify the reasonableness of model further, we made some simulation and simple analysis for the limb Stokes vector. Firstly, we made some simple simulation analysis about the limb vector radiative for the atmosphere with mineral-transported aerosol and the atmosphere with water-soluble aerosol at the wavelength320nm,380nm,440nm,500nm,560nm,600nm. The result show that the wavelength320nm,440nm,500nm,560nm,600nm have stronger ozone absorption. So the radiation intensity values is lower when we consider the ozone absorption. And the wavelength380nm have been little effected by the ozone absorption. The change of polarization radiation intensity is relatively consistent with the change of radiation intensity. The overall value of the degree of polarization is too large。We can’t ignore the effects of polarization.Secondly, the sensitivity of the observed position about the limb vector of radiation have been analyzed. The effect about the observed position for the limb vector radiative is large. The big change about the degree of polarization with the relative azimuth prove once again that the effects of polarization can’t be ignored.