用MODIS数据反演地表温度的基本参数估计方法

利用MODIS数据反演地表温度所需的2个基本参数(大气透过率和地表比辐射率)的估计方法,由MODIS的可见光近红外波段计算得到大气水汽含量,根据大气透过率与大气水汽含量的关系,用辐射传输模型MODTRAN模拟得到大气透过率.由于MODIS的扫描带宽为2 330 km,遥感视角和大气温度会对大气透过率有比较大的影响,因此,提出了大气透过率的遥感器视角校正函数和温度校正函数.地表比辐射率主要取决于地表物质构成,尤其是植被覆盖程度,为此,提出了根据地表植被覆盖差异来估计地表比辐射率的方法,其中还引入了辐射比率参数及其确定方法.

Estimation of the Basic Parameters for Deriving Surface Temperature from MODIS Data

Surface temperature is an important parameter in characterizing surface energy balance and a key parameter in monitoring farming drought,and is of very significance in the studies of global change,meteorology,hydrology,ecology,agricultural,etc.There are many factors affecting atmospheric transmittance, in which air vapor content is dominant.In this paper,the methods of estimating the 2 basic parameters(atmospheric transmittance and surface emissivity) for deriving surface temperature from MODIS data are discussed in detail.After calculating,air vapor content can be derived from the visible and near infrared bands of MODIS data,and then the atmospheric transmittance can be derived using atmospheric radiation transfer model MODTRAN based on the relationship between atmospheric transmittance and air vapor content.The sweep bandwidth of MODIS is 2 330 km and the RS angular field of view and atmospheric temperature affect significantly the atmospheric transmittance,so the calibration functions of RS angular field of view of atmospheric transmittance and of atmospheric temperature are used.Surface emissivity is mainly affected by land cover,especially by vegetation coverage,so the algorithm is developed for estimating surface emissivity based on land cover.Finally,an experiment of applying the methods is conducted to estimate the two parameters,and the results reveal that the methods of estimating the two parameters are applicable.