基于偏差原则利用MODIS红外资料反演大气廓线以及表层温度

Retrieval of atmospheric profiles and surface skin temperature from MODIS infrared data based on the discrepancy principle

遥感方程或大气辐射传输方程是属于第一类非线性Fredholm积分方程,这类方程的显著特征是不适定的,尤其此类问题解的不稳定性,增加了反演的难度。因此需要研究控制反演不稳定性和提高反演精度的有效方法。为了使解稳定,光滑参数γ作为约束因子是必要的。文中结合牛顿非线性迭代法反演大气廓线,利用偏差原则来最优选择光滑参数γ,即在同步反演大气廓线的同时对γ采用分步迭代的原则。最后利用中分辨率和成像光谱仪(MODIS)红外资料进行反演试验,反演结果表明采用偏差原则选取γ明显优于经验法,反演的表层温度和大气可降水量与美国国家宇航局(NASA)的MOD07产品类似。

It is known that a remote sensing or an atmospheric radiative transfer equation is a non-linear Fredholm integral equation of the first kind. As a result, it is illposed,the solution is unstable,and difficulties arise in its retrieval. So it is necessary to study the method of controlling instability of retrieval and to improve the accuracy of solution. To make the solution stable, a smoothing parameter γ needs to be used as a constraint. In this paper, atmospheric profiles are retrieved by using the Newton′s non-linear iteration method. We have developed a discrepancy principle （DP） to determine γ in an objective way. An approach is formulated for achieving an optimal solution for atmospheric profiles together with γ using step by step iterations. The DP method was applied to Moderate Resolution Imaging Spectroradiometer （MODIS） infrared data. The results show that the retrieved atmospheric profiles are better than with those from the empirical method,which uses a fixed smoothing parameter.The retrieved surface skin temperature and total precipitable water vapor （TPW） are as accurate as those of the MOD07 products.