比辐射率对遥感反演滇池流域地表温度的影响

为了探究地表比辐射率(以下简称“比辐射率”)对遥感反演地表温度的影响。利用Landsat5 TM6波段数据,以滇池流域为研究区域,通过NDVI阈值法和经验公式模型法求算比辐射率,应用普适性单通道算法反演得到滇池流域地表温度,结合滇池流域地面温度实测数据,分析不同比辐射率求算方法对反演地表温度的影响。结果表明: NDVI阈值法求算出的比辐射率和经验公式模型法求算出的比辐射率与MODIS比辐射率产品均显著相关;通过经验公式求算的比辐射率反演得到的城镇地区地表温度,超出观测温度4～5 ℃,不能精确地反映地表温度,而通过NDVI阈值法求算的比辐射率反演得到的地表温度更接近于地表实测温度,更能正确反映不同地表覆盖下的温度;由2种比辐射率反演得到的地表温度与实测温度差异较小,在精度控制范围之内。因此,对于滇池流域这种地表覆盖比较好的区域,用NDVI阈值法求算出的比辐射率来反演地表温度更为合适。

Effect of Emissivity on the Retrieved Land Surface Temperature from Remote Sensing Data of Dianchi Lake Watershed

Land surface temperature is an important indicator of analysing the earth’s environment, and land surface emissivity is a key factor on retrieved land surface temperature from remote sensing data. In this paper according to the measured land surface temperature, we analyzed the effect of different emissivity on the retrieved land surface temperature from remote sensing data. Firstly we calculated the land surface emissivity by using NDVI threshold method and empirical formula model respectively, and then adopted a generalized single-channel method to retrieve the land surface temperature. The Landsat5 TM6 band data acquired in March 24, 2009 in Dianchi Lake watershed was taken as research example. Results show that the emissivity calculated by both NDVI threshold method and empirical formula are in significant relation with MODIS validation data, and the retrieved surface temperature has small error compared with measured temperature, in the control range. But the surface temperature retrieved from the emissivity calculated by empirical formula is abnormal in urban areas, exceeding the observed temperature by 4 ℃ -5 ℃, which does not accurately reflect the surface temperature; while the surface temperature retrieved from the emissivity calculated by NDVI threshold method is nearer to the measured surface temperature, and reflects the temperature under different land covers more accurately. Therefore, for areas with good land cover such as Dianchi Lake watershed, it is more appropriate to retrieve land surface temperature from the emissivity calculated by NDVI threshold method.