基于NDVI阈值法反演地表比辐射率的参数敏感性分析

地表比辐射率是反演地表温度的重要因子,普遍应用于自然界中的水热交换和辐射传输过程。本文通过对基于NDVI阈值法反演地表比辐射率的相关参数进行敏感性研究,确定了影响NDVI阈值法反演地表比辐射率的关键参数,以期通过关键参数获取方法的改进和参数不确定性的降低来提高NDVI阈值法的反演精度。研究以Valor和Caselles在1996年提出的植被指数混合模型为理论基础、湖北省荆门市为研究区域,使用Land-sat TM5数据,采用控制变量法,对NDVI阈值法中影响比辐射率反演精度的大气因子、地形因子、纯像元NDVI阈值、纯像元比辐射率值进行敏感程度的数学分析。研究发现,4大因子敏感性程度:纯像元比辐射率值>纯像元NDVI阈值>地形因子>大气因子,其中纯像元比辐射率值和纯像元NDVI阈值为关键参数;4大因子影响程度:大气因子>纯像元比辐射率值>地形因子>纯像元NDVI阈值。

Sensitivity Analysis of Retrieving Land Surface Emissivity Based on NDVI Threshold Method

The land surface emissivity(LSE) is a significant parameter in the research on land surface characterization from remote sensing data,which is popularly applied to the process of water and heat exchange and radiative transfer.This paper examined the sensitivity analysis of retrieving land surface emissivity on the basis of NDVI threshold method,which was theoretically established on the vegetation index mixture model proposed by Valor and Caselles in 1996.We conducted a sensitivity analysis using Jingmen city of Hubei Province as a case study.The approach of controlling variables was used to identify the key parameters shaping significant effects on LSE retrieval from atmospheric and topographic factors.The effects of NDVI threshold and the emissivity value of pure pixels on LSE retrieval were also examined.The results showed that acquisition process and uncertainty of the key parameters had obvious effects on LSE retrieval.The research has discovered the degree sequence of sensitivity:the emissivity value of pure pixels> the NDVI threshold of pure pixels> topographic factors> atmospheric factors,meanwhile,the emissivity value and NDVI threshold of pure pixels had been identified as the key parameters,and the sequence of impact degree:atmospheric factors > the emissivity value of pure pixels > topographic factors> the NDVI threshold of pure pixels.