Gao Bo-Cai, Li Rong-Rong, Yang Yun, Anderson Martha
Remote Sensing Division, Code 7230, Naval Research Laboratory, Washington, DC 20375, USA.
Department of Forestry, Mississippi State University, Mississippi State, MS 39762, USA.
Sensors (Basel). 2024 Jul 19;24(14):4697. doi: 10.3390/s24144697.
Data from the Operational Land Imager (OLI) and the Thermal Infrared Sensor (TIRS) instruments onboard the Landsat 8 and Landsat 9 satellite platforms are subject to contamination by cloud cover, with cirrus contributions being the most difficult to detect and mask. To help address this issue, a cirrus detection channel (Band 9) centered within the 1.375-μm water vapor absorption region was implemented on OLI, with a spatial resolution of 30 m. However, this band has not yet been fully utilized in the Collection 2 Landsat 8/9 Level 2 surface temperature data products that are publicly released by U.S. Geological Survey (USGS). The temperature products are generated with a single-channel algorithm. During the surface temperature retrievals, the effects of absorption of infrared radiation originating from the warmer earth's surfaces by ice clouds, typically located in the upper portion of the troposphere and re-emitting at much lower temperatures (approximately 220 K), are not taken into consideration. Through an analysis of sample Level 1 TOA and Level 2 surface data products, we have found that thin cirrus cloud features present in the Level 1 1.375-μm band images are directly propagated down to the Level 2 surface data products. The surface temperature errors resulting from thin cirrus contamination can be 10 K or larger. Previously, we reported an empirical and effective technique for removing thin cirrus scattering effects in OLI images, making use of the correlations between the 1.375-μm band image and images of any other OLI bands located in the 0.4-2.5 μm solar spectral region. In this article, we describe a variation of this technique that can be applied to the thermal bands, using the correlations between the Level 1 1.375-μm band image and the 11-μm BT image for the effective removal of thin cirrus absorption effects. Our results from three data sets acquired over spatially uniform water surfaces and over non-uniform land/water boundary areas suggest that if the cirrus-removed TOA 11-μm band BT images are used for the retrieval of the Level 2 surface temperature (ST) data products, the errors resulting from thin cirrus contaminations in the products can be reduced to about 1 K for spatially diffused cirrus scenes.
陆地卫星8号和陆地卫星9号卫星平台上的陆地成像仪（OLI）和热红外传感器（TIRS）仪器所获取的数据容易受到云层覆盖的影响，其中卷云的影响最难检测和屏蔽。为了帮助解决这个问题，OLI上设置了一个位于1.375微米水汽吸收区域中心的卷云检测通道（波段9），其空间分辨率为30米。然而，在美国地质调查局（USGS）公开发布的第2版陆地卫星8号/9号二级地表温度数据产品中，这个波段尚未得到充分利用。这些温度产品是通过单通道算法生成的。在地表温度反演过程中，未考虑到对流层上部通常存在的冰云对来自较暖地球表面的红外辐射的吸收影响，冰云吸收红外辐射后会在低得多的温度（约220K）下重新发射。通过对一级顶空（TOA）和二级地表数据产品样本的分析，我们发现一级1.375微米波段图像中存在的薄卷云特征会直接传递到二级地表数据产品中。薄卷云污染导致的地表温度误差可能达到10K或更大。此前，我们报告了一种经验性且有效的技术，利用1.375微米波段图像与位于0.4 - 2.5微米太阳光谱区域的任何其他OLI波段图像之间的相关性，来消除OLI图像中的薄卷云散射效应。在本文中，我们描述了这种技术的一种变体，它可以应用于热波段，利用一级1.375微米波段图像与11微米亮度温度（BT）图像之间的相关性，有效消除薄卷云吸收效应。我们对在空间均匀的水体表面和非均匀的陆地/水体边界区域获取的三个数据集的分析结果表明，如果使用去除卷云后的一级11微米波段BT图像来反演二级地表温度（ST）数据产品，对于空间扩散的卷云场景，产品中由薄卷云污染导致的误差可降低至约1K。
