利用MODIS数据反演植被指数的敏感性研究

Numerical Experiment Study on the Sensitivity of Vegetation Indices from MODIS Data

根据Kaufman等提出的暗像元法,通过6S辐射传输模式,对MODIS的红光、蓝光、近红外通道辐射特性进行了敏感性实验.结果表明:三个通道的行星反射率对地表反射率都非常敏感,行星反射率随地表反射率的增加而增加.进一步提出了对地表反射率进行大气订正的思路,讨论了暗像元法确定地表反射率误差对大气气溶胶光学厚度反演结果的影响.最后计算分析了光学厚度反演误差对地表反射率大气订正传递误差的大小及其对NDVI、SAVI、ARVI和EVI 4种植被指数计算结果的影响.光学厚度误差对植被指数反演误差的影响以ARVI最为敏感,其误差范围与气溶胶光学厚度误差可达同一量级,两者呈负相关;NDVI与SAVI误差变化范围大致相近,与光学厚度误差均呈负相关.EVI受气溶胶光学厚度误差影响最小.

Based on the 6S radiative transfer model,the dark target（DT） method proposed by Kaufman was used to study the sensitivity of aerosol optical depth to the planetary albedo of three channels（blue,red,mid-infrared） of MODIS.The numerical experiment results showed that the planetary albedo of the three channels was highly sensitive to the surface albedo and increased linearly with increasing surface albedo.The impact of the surface albedo error due to the DT approach on the aerosol optical properties was studied to propose a correct method.At the same time,the correction error and its impact on the four vegetation indexes（NDVI,SAVI,ARVI and EVI） were calculated.ARVI was shown to be the most sensitive index which had the same order of error as AOD,but EVI was not sensitive to the error of AOD,and NDVI and SAVI had similar error ranges,which were in a negative correlation with AOD.