MODIS Atmosphere: Data Issues for C6 07

Tracking of known problems and subsequent fixes is an important issue for MODIS data users. This page will act as a repository of all known MODIS Atmosphere Data Product problems, as well as how to determine the problematic version (and the fixed version) of the HDF 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 HDF files should refer to the documentation at the bottom of this page.

Collection 006 Issues

Click the colored buttons below for the known problems associated with each MODIS Atmosphere Data Product in Collection 6.

Incorrect Terra IR Water Vapor Profiles from Band 27 Crosstalk

Description: April 2016 update from PGE03 developers: A band 27 cross-talk problem, that increased (and became more pronounced) over time starting around 2010, produced incorrect IR Water Vapor profiles, with artificially low moisture content in the middle atmospheric layer and excessively high values in the upper troposphere. The MCST is still investigating possible fixes for this problem. Users should note that the IR Water Vapor profile data is in an SDS called "Water_Vapor", "Water_Vapor_Low", and "Water_Vapor_High" in the 07_L2 file.
Impact: High
Data Dates Affected: 2010 and on (but worse 2014 and on)
Platform Affected: Terra Only

PGE Version Production Dates PGE Version Production Dates

≥ 2010 Not Corrected Not Corrected

Unstable Atmospheric Profile Retrievals over Antarctica

Description: In collection 006, the cloud mask is failing to detect high thick clouds over the Weddell Sea area when it is ice-covered. This represents a small area over very dry conditions, but it is causing high and noisy retrievals (high standard deviation) in the integrated water vapor values (440-10 hPa) and unrealistic values in the Retrieved Temperature Profiles and Total Ozone. These problem pixels can be filtered out by users with additional sanity checks until it is fixed in the future PGE03 delivery.
Impact: Low
Data Dates Affected: 7/2002-current
Platform Affected: Aqua Only

PGE Version Production Dates PGE Version Production Dates

≤ PGE03 v6.0.40 All (not corrected) (not corrected)

Suspect Atmosphere Profile Retrievals at Night

Description: There was a problem in the Collection 6 (C6) Atmosphere Profile Product for nighttime data only. In the nighttime granules, an error occurred in selecting the proper GDAS (NCEP 1-Degree Global Data Assimilation Model) re-analyses ancillary data file. Instead of selecting the file closest in time with a less than 3 hour time differences between the GDAS time and the granule time, the algorithm selected the wrong GDAS file time resulting in as much as a 6 hour time difference. The MOD07 algorithm uses the surface pressure variable of the GDAS reanalyses to determine the lowest level of the atmospheric temperature, moisture, and ozone profiles. To set the lowest level as accurate as possible is very important for integrating the water vapor content of the column and the layer mean of water vapor close to the surface. The error affected the 07 L2 SDS's "Surface_Pressure", "Water_Vapor", "Water_Vapor_Low" as well as levels of the Temperature Profile and Moisture Profile close to the surface. The values were just "marginally off" but affected all granules globally.
Impact: Moderate
Data Dates Affected: 7/2002-7/2014
Platform Affected: Aqua (Nighttime Granules) Only

PGE Version Production Dates PGE Version Production Dates

≤ PGE03 v6.0.39 ≤ 2014 182 (7/1/2014) ≥ PGE03 v6.0.40 ≥ 2014 190 (7/9/2014)

Latest PGE Version Available (by Data Date)

Shown below is a bar chart graphic summarizing the latest Product Generation Executive (PGE) Version used to produce Collection 6 (C6) 07_L2 HDF files available for public distribution (download) in the LAADS data archive. This graphical representation gives MODIS data users a summary guide (digestable at a glance) on how the PGE Version varies across the multi-year data record. Each PGE version contains a unique set of fixes and improvments and show where data quality discontinuities can occur. If MODIS data users have older versions of any of the data shown below, they should download the newer (more correct) version from either: LAADS FTP (Download C6 MYD07_L2 Data) or LAADS Web (Search & Order MODIS Data)

Aqua Daytime Granules:

Aqua Nighttime Granules:

How to Track MODIS Data File "Versions" (Important for Tracking Problems and Fixes)

Problems and fixes in MODIS Atmosphere Product HDF files can be tracked in one of two ways:

the Product Generation Executive (PGE) Version Number that can be queried from any HDF file using the command:
ncdump -h *.hdf

the HDF File "Production Date".

The HDF File "Production Date", which is the date the HDF file was actually generated or produced, can be found in the HDF filename itself (shown in green color below):

Level 2 Product Names:

Level 3 Product Names:

Note that 1.) all times are UTC time, not local time 2.) the DDD in the date denotes the Julian Date (001-366), and 3.) the MOD06_L2 (or MOD08_D3) prefix is only an example (MYD04_L2, MOD05_L2, MYD05_L2, MYD06_L2, etc. ... or MYD08_D3, MOD08_E3, MYD08_E3, MOD08_M3, MYD08_M3 could be substituted).