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Collection 051 Update

Collection 051 The document below describes proposed Collection 051 changes to all L2 and L3 MODIS data. The next generation of MODIS data products, tagged Collection 051, is expected to began production in November 2008.

Collection 051 Change Summary Document

  • Collection 051 Change Document v1.0 (PDF) View the PDF Document





Collection 051 Problems

    Bad data in a subset of Collection 051

    An error involving incorrect Clear Sky Radiances was found in a subset of Terra Collection 051. This adversely affected all cloud-related parameters in both Level-2 and Level-3 for the impacted subset.

    How To Identify Bad C051 Data

    All Cloud-related (MOD06_L2, MODATML2, MOD08_D3, MOD08_E3, and MOD08_M3) Collection 051 Terra HDF files with a data date prior to April 1, 2010 (2010 091) and a processing date prior to September 28, 2010 (2010 271) is bad. Note that this error did not impact Terra C051 HDF files with data dates on or after April 1, 2010 (2010 091); nor did this error impact any Aerosol or Water Vapor SDS's. Both the data date and production date are a part of the HDF filename. A new corrected Collection 051 Terra reprocessing effort began again on calendar date September 28, 2010 (2010 271) and is now completed.

    Users of cloud-related HDF product files should replace any bad data files with the latest reprocessed C051 data from the LAADS website, the distributor of MODIS data.

    It should be noted that any Collection 051 HDF data file with a data date on or after April 1, 2010 (2010 091) was not impacted by this problem and is considered correct.

    Below is a sample HDF file name, along with the 4 keys on how it can be identified as bad data:


    View the MODIS Data Processing & Availability Calendar to see the status of data availabile in various Collections.

         


Comparison of Good Collection 051 Data with Bad Collection 051 Data

An error involving incorrect Clear Sky Radiances was found in a subset of Terra Collection 051. This adversely affected all cloud-related parameters in both Level-2 and Level-3 for the impacted subset.

Roll your mouse pointer over the rectangular bars to the right of each image below, to see how the data changed on this particular day with good and bad Clear Sky Radiance input data.

The change (error) is much more noticeable in Level-2 5x5 km granule data (top image) than in the coarser resolution Level-3 1x1 degree global gridded data (bottom images).

The largest error is in the Cloud Top Pressure data; much smaller (more subtle) errors can be seen in downstream Cloud products like Cloud Optical Thickness and Cloud Effective Radius. Because the errors are more difficult to see in the L3 data, difference maps have been provided (roll your mouse over the 3rd rollover bar to the right of each L3 image).




-------------------------
Level-2 Granule Data
-------------------------

Cloud Top Pressure -- Collection 005 (good data) vs. Collection 519 (bad data)
CTP
 
C005Collection 005  [Good]
C519Collection 519  [Bad]
roll mouse over bars



---------------------
Level-3 Daily Data
---------------------

Level-3 Daily Cloud Top Pressure Daytime -- Collection 005 (good data) vs. Collection 519 (bad data)
CTP
 
C005Collection 005  [Good]
C519Collection 519  [Bad]
DifferenceC519-C005  [Difference]
roll mouse over bars

Level-3 Daily Cloud Optical Thickness Liquid -- Collection 005 (good data) vs. Collection 519 (bad data)
COTL
 
C005Collection 005  [Good]
C519Collection 519  [Bad]
DiffC519-C005  [Difference]
roll mouse over bars

Level-3 Daily Cloud Effective Radius Liquid -- Collection 005 (good data) vs. Collection 519 (bad data)
CERL
 
C005Collection 005  [Good]
C519Collection 519  [Bad]
DiffC519-C005  [Difference]
roll mouse over bars




-------------------------
Level-3 Monthly Data
-------------------------

Level-3 Monthly Cloud Top Pressure Daytime -- Collection 005 (good data) vs. Collection 519 (bad data)
CTP
 
C005Collection 005  [Good]
C519Collection 519  [Bad]
DiffC519-C005  [Difference]
roll mouse over bars


Level-3 Monthly Cloud Optical Thickness Liquid-- Collection 005 (good data) vs. Collection 519 (bad data)
COTL
 
C005Collection 005  [Good]
C519Collection 519  [Bad]
DiffCollection 519  [Bad]
roll mouse over bars


Level-3 Monthly Cloud Effective Radius Liquid -- Collection 005 (good data) vs. Collection 519 (bad data)
CERL
 
C005Collection 005  [Good]
C519Collection 519  [Bad]
DiffC519-C005  [Difference]
roll mouse over bars