Cloud detection with MODIS. Part I: Improvements in the MODIS cloud mask for collection 5
Cloud detection with MODIS. Part I: Improvements in the MODIS cloud mask for collection 5
复制标题
DOI：
10.1175/2008jtecha1052.1
复制
发表时间：
2008-07-01
影响因子：
2.2
通讯作者：
Wang, Xuangi
中科院分区：
文献类型：
--
作者：
Frey, Richard A.;Ackerman, Steven A.;Wang, Xuangi
对用于Collection 5再处理和前向流数据生成的中分辨率成像光谱仪（MODIS）云掩模（MOD 35和MYD 35）进行了重大改进。大部分的修改都是针对夜间场景实现的，极地和海洋区域将有明显的改善。对于极地夜景，增加了两个新的光谱测试，使用7.2 μ m的水汽吸收带，以及更新3.9 - 12 μ m和11 - 12 μ m的云测试。增加了更多的非中分辨率成像分光仪辅助输入数据。陆地和海洋表面温度图为中低层云探测提供了重要信息，并减少了对海洋亮温变化测试的依赖。利用海面温度也可以改善太阳闪烁区，以帮助解决观测结果与云与晴空信号相冲突的问题，其中可见光和近红外（NIR）反射率很高，但红外亮度温度相对较暖。白天和夜间北极云频率的结果相比，由高级甚高分辨率辐射计（AVHRR）极地探路者扩展（APP-X）算法创建的。白天与夜间的海面温度来自MODIS辐射和只使用MODIS云屏蔽云进行对比。来自太阳闪烁区域的云的频率被示出为太阳闪烁角的函数，以获得在这些区域中的云掩模质量的感觉。本文件第II部分描述了持续验证活动。
Significant improvements have been made to the Moderate Resolution Imaging Spectroradiometer (MODIS) cloud mask (MOD35 and MYD35) for Collection 5 reprocessing and forward stream data production. Most of the modifications are realized for nighttime scenes where polar and oceanic regions will see marked improvement. For polar night scenes, two new spectral tests using the 7.2-mu m water vapor absorption band have been added as well as updates to the 3.9-12- and 11-12-mu m cloud tests. More non-MODIS ancillary input data have been added. Land and sea surface temperature maps provide crucial information for mid- and low-level cloud detection and lessen dependence on ocean brightness temperature variability tests. Sun-glint areas are also improved by use of sea surface temperatures to aid in resolving observations with conflicting cloud versus clear-sky signals, where visible and near-infrared (NIR) reflectances are high, but infrared brightness temperatures are relatively warm. Day and night Arctic cloud frequency results are compared to those created by the Advanced Very High Resolution Radiometer (AVHRR) Polar Pathfinder-Extended (APP-X) algorithm. Day versus night sea surface temperatures derived from MODIS radiances and using only the MODIS cloud mask for cloud screening are contrasted. Frequencies of cloud from sun-glint regions are shown as a function of sun-glint angle to gain a sense of cloud mask quality in those regions. Continuing validation activities are described in Part II of this paper.