Skip to main content

CLDMSK_L2 Issues

Tracking of known problems and subsequent fixes is an important issue for Continuity Atmosphere data users. This page will act as a repository of all known Continuity Atmosphere Data Product problems, as well as how to determine the problematic version (and the fixed version if available) of the NetCDF4 data -- therefore data users should check this page for updates regularly. Data Users unfamiliar with how to properly track problems and fixes by determining the version of their downloaded NetCDF4 files should refer to the documentation in the Introduction sublink (the top link along the LHS of this page).   

Note that a checkmark (✔) in the tables below means Data Issue or Quality Statement applies.  A blank means it's been fixed or does not apply.

 




L2 Cloud Mask (CLDMSK_L2) Data Issues: Table of Contents & Anchor Links  

(Note: Anchor Links point to a specific place within this page.)

Collection/Platform where Issues Apply 
Issue Impact    

MODIS

VIIRS

Link
#1. Degraded Geolocation required Reprocessing  H    

 

Link
#2.  Bad Refl. Band Cal. required Reprocessing L    

 

Link

L2 Cloud Mask (CLDMSK_L2) Data Quality Statements: Table of Contents & Anchor Links  

(Note: Anchor Links point to a specific place within this page.)

Collection/Platform where Quality Statements Apply 
Quality Statement Impact    

MODIS

VIIRS

Link
#1. New Calibration Impact Q    

Link

 




Issue #1: Degraded Geolocation for VIIRS SNPP data between 20 Dec 2019 and 6 Jan 2020 required reprocessing

Description:  SNPP VIIRS Continuity Atmosphere L2 and L3 products had degraded geolocation data during the indicated time period which warranted a reprocessing.  Affected products have filenames that begin with AERDB, AERDT, CLDMSK, CLDPROP, and FSNRAD.  (Note that FSNRAD is the L2 VIIRS and CrIS fusion product for SNPP and J1 (NOAA-20), where FSN stands for “fusion”.)  Version 1.0 data during the indicated time period should be replaced by filenames with creation timestamps on or after January 8th 2020 (2020 008).

 

PGE Versions & Production Dates of Problematic & Corrected Data:

Problematic Data  Corrected Data

PGE Versions

Production Dates

PGE Versions

Production Dates

CLDMSK_L2 v1.0

< 2020 008 (01/08/20)

CLDMSK_L2 v1.0

≥ 2020 008 (01/08/20)

Data Dates Affected: 20 December 2019 (Day 354) starting at 13:54:00 UTC and forward through 6 Jan 2020 (Day 006) ending at 13:53:59 UTC

Affected Platform: VIIRS SNPP

Versions Affected: Version.1.0

Return to Menu at Top of Page

 


Issue #2: Incorrect VIIIRS Reflective Band Calibration on 16-17 Jan 2020 required reprocessing

Description:  SNPP VIIRS data users, please note that the quality of all NASA Level-1 data and derived downstream products were likely affected by incorrect solar and lunar vector calculations between 2020-016 and 2020-017. The VIIRS Characterization Support Team (VCST) delivered an updated planetary ephemeris look-up table that corrected this anomaly, at which point all affected datasets were reprocessed. For additional details on this anomaly, check the Land Data Operational Products Evaluation (LDOPE) group’s description: https://tinyurl.com/qwfsgpw

 

PGE Versions & Production Dates of Problematic & Corrected Data:

Problematic Data  Corrected Data

PGE Versions

Production Dates

PGE Versions

Production Dates

CLDMSK_L2 v1.0

< 2020 017 (01/17/20)

CLDMSK_L2 v1.0

≥ 2020 017 (01/17/20)

Data Dates Affected: 16 January 2020 (Day 016) starting at 00:00:00 UTC and forward through 17 Jan 2020 (Day 017) ending at 12:00:00 UTC

Affected Platform: VIIRS SNPP

Versions Affected: Version.1.0

Return to Menu at Top of Page

 




Quality Statement #1: Expected Changes with New Calibration (August 2023)

Premise: .The Cloud Mask Group compared the operational Continuity Cloud Mask output (v1.0.3 for S-NPP and v1.0.4 for NOAA-2) versus the new 1.0.5dev0.  Note that v1.0.3 uses old calibration S-NPP L1B and MVCM20190117-1, which sets Clear Sky Confidence to 1 when the retrieval is not performed.  And v1.0.4 uses old calibration NOAA-20 L1B and MVCM 20201008-1, which sets Clear Sky Confidence to -1 (i.e. fill value) when the retrieval is not performed.  Finally, v1.0.5dev0 uses new calibration (both S-NPP and NOAA-20) and MVCM 20201008-1.  It should be remembered that some files were missing for January comparison of NOAA-20, which helps to explain some of the large differences seen for that sensor.

Cumulative Distribution of CSC and ICM Differences:   There was negligible impact of the L1B change for both SNPP and NOAA 20 -- Over 99.9% of values were within ± 0.02 for SNPP and ± 0.08 for NOAA 20.  Finally, the new SST input had only a minimal impact with 99.9% of values displaying a minor ± 0.07 difference.

Conclusions: 1.)  Large differences in polar regions for SNPP comparison are explained by use of different versions of MVCM (MODIS VIIRS Cloud Mask). 2.) The change in calibration has only a minimal impact in the MVCM output. 3.) Changing the SST does not affect the MVCM output significantly

Supporting Document:  PDF Document Containing Images 

Return to Menu at Top of Page