MODIS/Terra Clouds 5-Min L2 Swath 1km and 5km - NRT

The level-2 MODIS cloud product consists of cloud optical and physical parameters. These parameters are derived using remotely sensed infrared, visible and near infrared solar reflected radiances. MODIS infrared channel radiances are used to derive cloud top temperature, cloud top height, effective emissivity, cloud phase (ice vs. water, opaque vs. non-opaque), and cloud fraction under both daytime and nighttime conditions. MODIS visible radiances are used to derive cloud optical thickness and effective particle radius and cloud shadow effects. Near infrared solar reflected radiance provides additional information in the retrieval of cloud particle phase (ice vs. water, clouds vs. snow). The shortname for this level-2 MODIS cloud product is MOD06_L2.MOD06_L2 consists of parameters at a spatial resolution of either 1- km or 5-km (at nadir). Each MOD06_L2 product file covers a five-minute time interval. This means that for 5-km resolution parameters, the output grid is 270 pixels in width by 406 pixels in length.

On 18 February 2016, the Terra spacecraft, and therefore MODIS, unexpectedly entered safe hold
mode during an inclination adjustment maneuver (IAM). After resuming operation on 24 February
2016, several infrared (IR) channels exhibited significant degradation, namely increased electronic
cross talk in the 8.5μm (Band 29) and immediately surrounding channels. This cross talk,
manifesting as a “warming” of Band 29, exacerbated a previously identified Band 29 “warming”
(cross talk) trend that caused a spurious cloud mask trend over the tropics starting around 2010.
Following extensive analysis, a cross talk correction was developed for the affected IR channels,
and the decision was made to reprocess the entire Terra-MODIS L1B record to include this fix.
The Atmosphere Team subsequently decided to piggyback the Terra-MODIS L1B reprocessing
effort to implement numerous low-impact updates to the C6 atmosphere products.

C6.1 changes for the cloud optical property retrievals are low-impact, and are limited primarily
to ancillary product usage, the Quality Assurance (QA), and handling of cloud top (CT) properties
fill values; no updates to retrieval science are implemented.

For more information about the MODIS Cloud product, visit the MODIS-Atmosphere site at:

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

For more details regarding dataset changes read the document at https://modis-atmos.gsfc.nasa.gov/documentation/collection-61

第二级 MODIS 云产品包含云的光学及物理参数。这些参数通过遥感探测的红外、可见光及近红外太阳反射辐射率推导得出。MODIS 红外通道辐射率被用于推导云顶温度、云顶高度、有效发射率、云相（冰与水、不透明与半透明）以及昼夜条件下的云量。MODIS 可见光辐射率被用于推导云光学厚度、有效粒子半径和云阴影效应。近红外太阳反射辐射率在云粒子相（冰与水、云与雪）的检索中提供了额外的信息。该第二级 MODIS 云产品的简称是 MOD06_L2。MOD06_L2 包含的空间分辨率为 1 公里或 5 公里（正对点）。每个 MOD06_L2 产品文件覆盖五分钟的时间间隔。这意味着对于 5 公里分辨率的参数，输出网格的宽度为 270 像素，长度为 406 像素。

2016 年 2 月 18 日，在倾斜调整机动（IAM）过程中，Terra 航天器以及随之的 MODIS 突然进入安全保持模式。在 2016 年 2 月 24 日恢复操作后，几个红外（IR）通道表现出显著的退化，即 8.5 微米（波段 29）及其邻近通道的电子串扰增加。这种串扰，表现为波段 29 的“升温”，加剧了之前识别出的波段 29 的“升温”（串扰）趋势，导致大约从 2010 年开始热带地区的云掩码趋势出现异常。经过广泛的分析，为受影响的红外通道开发了一种串扰校正方法，并决定重新处理整个 Terra-MODIS L1B 记录以包含这一修正。大气团队随后决定将 Terra-MODIS L1B 重新处理工作作为附加任务，以实施对 C6 大气产品的一系列低影响更新。

C6.1 对云光学特性检索的更改影响较小，主要限于辅助产品使用、质量保证（QA）以及云顶（CT）属性填充值的处理；未实施任何检索科学的更新。

欲了解更多关于 MODIS 云产品信息，请访问 MODIS-大气网站：

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

有关数据集变更的详细信息，请参阅文档：

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