MODIS/Terra+Aqua BRDF/Albedo White Sky Albedo Band4 Daily L3 Global 30ArcSec CMG V006

The MCD43D55 Version 6 data product was decommissioned on July 31, 2023. Users are encouraged to use the [MCD43D55 Version 6.1](https://doi.org/10.5067/MODIS/MCD43D55.061) data product.

The MCD43D55 Version 6 Bidirectional Reflectance Distribution Function and Albedo (BRDF/Albedo) White-Sky Albedo dataset is produced daily using 16 days of Terra and Aqua Moderate Resolution Imaging Spectroradiometer (MODIS) data at 30 arc second (1,000 meter (m)) resolution. Data are temporally weighted to the ninth day which is reflected in the Julian date in the file name. This Climate Modeling Grid (CMG) product covers the entire globe for use in climate simulation models. Due to the large file size, each MCD43D product contains just one data layer.

MCD43D42 through MCD43D61 are the albedo products of the MCD43D BRDF/Albedo product suite. There are 10 black-sky albedo and 10 white-sky albedo layers representing MODIS bands 1 through 7 and the visible, near-infrared (NIR), and shortwave bands. The black-sky albedo (directional hemispherical reflectance) is defined as albedo in the absence of a diffuse component and is a function of solar zenith angle. White-sky albedo (bihemispherical reflectance) is defined as albedo in the absence of a direct component when the diffuse component is isotropic.

MCD43D55 is the white-sky albedo for MODIS band 4.

Users are urged to use the band specific quality flags to isolate the highest quality full inversion results for their own science applications as described in the [User Guide](https://www.umb.edu/spectralmass/modis-user-guide-v006-and-v0061/mcd43d-cmg-30-arc-second-products/).

Known Issues
* The incorrect representation of the aerosol quantities (low average high) [in the C6 MYD09 and MOD09 surface reflectance products](https://landweb.modaps.eosdis.nasa.gov/displayissue?id=86) may have impacted downstream products particularly over arid bright surfaces. This (and a few other issues) have been corrected for C6.1. Therefore users should avoid substantive use of the C6 MCD43 products and wait for the C6.1 products. In any event, users are always strongly encouraged to download and use the extensive QA data provided in MCD43A2, in addition to the briefer mandatory QAs provided as part of the MCD43A1, 3, and 4 products.
* [Corrections](https://landweb.modaps.eosdis.nasa.gov/data/userguide/LSRHighAerosolFlagFinal.pdf) were implemented in Collection 6.1 reprocessing.
* For complete information about the MCD43D55 known issues refer to the [MODIS Land Quality Assessment website](https://landweb.modaps.eosdis.nasa.gov/knownissue?sensor=MODIS&as=6).

MCD43D55 Version 6数据产品已于2023年7月31日退役。建议用户使用[MCD43D55 Version 6.1](https://doi.org/10.5067/MODIS/MCD43D55.061)数据产品。

MCD43D55 Version 6双向反射分布函数与反照率（Bidirectional Reflectance Distribution Function and Albedo, BRDF/Albedo）晴空反照率数据集，每日基于16天的Terra和Aqua中分辨率成像光谱仪（Moderate Resolution Imaging Spectroradiometer, MODIS）数据生成，分辨率为30角秒（1000米，m）。数据以第9日为时间加权基准，该信息可通过文件名中的儒略日体现。该气候建模网格（Climate Modeling Grid, CMG）产品覆盖全球，可用于气候模拟模型。由于文件体积较大，每个MCD43D系列产品仅包含一个数据层。

MCD43D42至MCD43D61属于MCD43D系列BRDF/反照率产品套件中的反照率产品。其中包含10层黑空反照率与10层晴空反照率，对应MODIS第1至7波段以及可见光、近红外（Near-Infrared, NIR）和短波波段。黑空反照率（方向半球反射率）被定义为无漫射分量时的反照率，是太阳天顶角的函数。晴空反照率（双半球反射率）被定义为无直射分量且漫射分量各向同性时的反照率。

MCD43D55对应MODIS第4波段的晴空反照率。

建议用户按照[用户指南（User Guide）](https://www.umb.edu/spectralmass/modis-user-guide-v006-and-v0061/mcd43d-cmg-30-arc-second-products/)中的说明，使用波段专属质量标志筛选出最高质量的全反演结果，以用于自身的科学研究应用。

已知问题
* C6版本的MYD09和MOD09地表反射率产品中存在气溶胶数量表征错误（平均偏低偏高）[https://landweb.modaps.eosdis.nasa.gov/displayissue?id=86]，可能对下游产品造成影响，尤其是在干旱亮面区域。该问题（以及其他若干问题）已在C6.1版本中得到修正。因此，应避免大量使用C6版本的MCD43D系列产品，等待C6.1版本产品发布。无论如何，强烈建议用户除使用MCD43A1、3、4产品中附带的简短强制质量评估（Quality Assurance, QA）数据外，一并下载并使用MCD43A2中提供的全面质量评估数据。
* [修正方案](https://landweb.modaps.eosdis.nasa.gov/data/userguide/LSRHighAerosolFlagFinal.pdf)已在C6.1重处理流程中实施。
* 如需了解MCD43D55已知问题的完整信息，请参阅[MODIS陆地质量评估网站](https://landweb.modaps.eosdis.nasa.gov/knownissue?sensor=MODIS&as=6)。