不依赖现场数据的ASTER海表温度反演方法

A method for SST retrieval from ASTER image without using in-situ data

利用大气传输模拟程序MODTRAN(moderate resolution atmospheric radiance and transmission),以同步的中分辨率成像光谱仪(moderate resolution imaging spectroradiometer,MODIS)二级产品的大气廓线数据作为输入,模拟先进星载热发射和反射辐射计(advanced spaceborne thermal emission and reflection radiometer,ASTER)热红外波段的大气波谱透过率和大气上、下行波谱辐射。结合ASTER的波谱响应函数和喷气推进实验室(Jet Propulsion Laboratory,JPL)数据库提供的海面发射率,在波谱上求解各像元辐射传输方程。求解获得5个波段海表温度,当这5个波段的海表温度值两两之间温差不超过0.5K时,将其平均值作为该像元的海表温度,用以拟合分裂窗算法的待定系数,最后用分裂窗算法获得整个ASTER图像内的海表温度产品。该算法具有比较高的反演精度,与MODIS的海表温度(SST)产品对比,平均偏差为0.35℃,均方根误差0.49℃,而且具有较好的适应能力。将2007年10月20日ASTER图像数据建立的分裂窗算法应用到2008年5月15日的ASTER数据,海表温度反演结果与MODIS的SST产品相比,平均偏差为0.38℃,两者均方根误差为0.52℃。

The moderate resolution atmospheric radiance and transmission （MODTRAN）, with the input parameters obtained from Terra/MODIS （moderate resolution imaging spectroradiometer）, was used to calculate the atmospheric effect parameters, including atmospheric transmittance, upward radiance and downward radiance. Combined with the sea surface emissivity provided by the Jet Propulsion Laboratory （JPL） and spectral response functions for five bands of advanced spaceborne thermal emission and reflection radiometer （ASTER） sensor, the sea surface temperatures （SST） were solved from radiative transfer equations pixel by pixel for each band. If the difference between any two bands’ SSTs for the same pixel is less than 0.5K, the average of five bands’ SSTs of the pixel was taken as true SST, which was then used to derive the undetermined coefficients of Split-Window algorithm. Finally, the Split-Window algorithm was applied for the SST retrieval. The results showed the algorithm has good accuracy. The SST values retrieved from ASTER data acquired on October 20, 2007 were compared to the MODIS SST, which gives the mean deviation of 0.35℃and the root-mean-squared error （RMSE） of 0.49℃. The same procedure was repeated for ASTER data acquired on May 15, 2008, which gives the mean deviation of 0.38℃and RMSE of 0.52℃.