MODIS/Terra Cloud Mask and Spectral Test Results 5-Min L2 Swath 250m and 1km - NRT

The MODIS level-2 cloud mask product is a global product generated for both daytime and nighttime conditions at 1-km spatial resolution (at nadir) and for daytime at 250-m resolution. The algorithm employs a series of visible and infrared threshold and consistency tests to specify confidence levels that an unobstructed view of the Earth's surface is observed.

The Terra MODIS Photovoltaic (PVLWIR) bands 27-30 are known to experience an electronic crosstalk contamination. The influence of the crosstalk has gradually increased over the mission lifetime, causing for example, earth surface features to become prominent in atmospheric band 27, increased detector striping, and long term drift in the radiometric bias of these bands. The drift has compromised the climate quality of C6 Terra MODIS L2 products that depend significantly on these bands, including cloud mask (MOD35), cloud fraction and cloud top properties (MOD06), and total precipitable water (MOD07). A linear crosstalk correction algorithm has been developed and tested by MCST.The electronic crosstalk correction was made to the calibration algorithm for bands 27-30 and implemented into C6.1 operational L1B processing. This implementation greatly improves the performance of the cloud mask.

For more information on C6.1 changes visit:

https://modis-atmos.gsfc.nasa.gov/documentation/collection-61

The shortname for this Level-2 MODIS cloud mask product is MOD35_L2 and the principal investigator for this product is MODIS scientist Dr. Paul Menzel ( [e-mail]). MOD35_L2 product files are stored in Hierarchical Data Format (HDF-EOS). Each of the 9 gridded parameters is stored as a Scientific Data Set (SDS) within the HDF-EOS file. The Cloud Mask and Quality Assurance SDS's are stored at 1 kilometer pixel resolution. All other SDS's (those relating to time, geolocation, and viewing geometry) are stored at 5 kilometer pixel resolution.

Link to the MODIS homepage for more data set information:

https://modis-atmos.gsfc.nasa.gov/products/cloud-mask

MODIS二级云掩膜产品是一种全球性产品，旨在白天和夜晚条件下以1公里空间分辨率（在视场中心）以及白天250米分辨率生成。该算法采用一系列可见光和红外阈值及一致性测试，以确定观测到地球表面无遮挡视野的置信水平。已知Terra MODIS光生伏打（PVLWIR）波段27-30存在电子串扰污染。随着任务周期的延长，串扰的影响逐渐加剧，例如，地球表面特征在大气波段27中变得突出，探测器条纹增加，以及这些波段辐射测量偏差的长期漂移。这种漂移削弱了依赖于这些波段（包括云掩膜（MOD35）、云量及云顶特性（MOD06）和总可降水量（MOD07））的C6 Terra MODIS L2产品的气候质量。MCST开发并测试了一种线性串扰校正算法，对波段27-30的校准算法进行了电子串扰校正，并将其应用于C6.1操作L1B处理。这一实施显著提高了云掩膜的性能。欲了解更多关于C6.1变更的信息，请访问：

https://modis-atmos.gsfc.nasa.gov/documentation/collection-61

此二级MODIS云掩膜产品的简称是MOD35_L2，该产品的首席研究员为MODIS科学家保罗·门泽尔博士（[e-mail]）。MOD35_L2产品文件存储在层次数据格式（HDF-EOS）中。9个网格化参数中的每一个都存储在HDF-EOS文件中的科学数据集（SDS）内。云掩膜和质量保证SDS存储在1公里像素分辨率。所有其他SDS（与时间、地理定位和观测几何相关）存储在5公里像素分辨率。有关更多数据集信息的MODIS主页链接：

https://modis-atmos.gsfc.nasa.gov/products/cloud-mask