利用FY-2G(风云二号G星)静止气象卫星中红外和热红外通道白天/夜晚数据进行我国陆地区域地表发射率的反演。采用欧洲中期天气预报中心(ECMWF)提供的温湿度、臭氧等大气廓线数据,基于辐射传输模型MODTRAN进行遥感影像的大气校正;选用修正后的Minnaert双向反射分布函数计算中红外通道地表方向的半球反射率,基于与温度无关的热红外光谱指数(TISI),最终得到我国不同地表植被类型下白天和夜晚的地表发射率分布特征;然后选取MODIS地表发射率产品对我国陆地区域的影像进行地表发射率反演结果的验证,结果显示:白天和夜晚的地表发射率反演结果与MODIS现有地表发射率产品吻合得较好,白天热红外通道IR1、IR2地表发射率反演的绝对误差分别为-0.0057、-0.0068,均方根误差分别为0.0095、0.0103;夜晚的绝对误差分别为-0.0010、-0.0035,均方根误差分别为0.0094、0.0096。同时对同一天不同时刻的地表发射率反演结果进行分析,结果表明,夜间的地表发射率略低于白天。

In this study, we present the inversion of land surface emissivity (LSE) in the China land area based on the mid-infrared and thermal infrared channel day/night data received by the FengYun-2G (FY-2G) geostationary meteorological satellite. The atmospheric correction of the FY-2G data is based on MODTRAN, which is a radiation transfer model, using the atmospheric profile data, including data with respect to the temperature, humidity, and ozone, provided by the European Centre for Median-range Weather Forecast (ECMWF). The modified Minnaert’s bidirectional reflection distribution function model is used to calculate the hemispherical reflectivity of the mid-infrared channel in the surface direction. Further, the LSE distribution characteristics can be obtained with respect to the different surface vegetation types in China based on the temperature-independent thermal infrared spectral index. Finally, the LSE inversion results obtained from the images of China’s land area are verified by selecting the surface emissivity products from Moderate Resolution Imaging Spectroradiometer (MODIS). The daytime and nighttime results are observed to be in good agreement with the existing LSE products in MODIS. The absolute LSE inversion errors of the hot infrared channels 1 and 2 during daytime are -0.0057 and -0.0068, respectively, and the root mean square errors (RMSEs) are 0.0095 and 0.0103, respectively. Furthermore, the absolute LSE inversion errors of the hot infrared channels 1 and 2 during nighttime are -0.0010 and -0.0035, respectively, and the RMSEs are 0.0094 and 0.0096, respectively. Simultaneously, the LSE inversion results at different time slots on the same day are analyzed. These results indicate that the LSE at nighttime is lower than that at daytime.