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