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OMI INFORMATION

 Technical Information for OMI Data Users

Several row anomalies have occurred in the recent past. These anomalies affect the quality of the Level 1B and Level 2 data products. Please read this information carefully prior to using OMI data. Please respect the dates mentioned as the anomalies have occurred recently.

Anomaly 1

Since June 25th, 2007 an anomaly is present in (cross-track) scenes 53-54 (0-based). The anomaly comprises a decrease in the radiance signal, with secondary effects.

The Level 1B data has been flagged for this anomaly for (cross-track) scenes 53-54 (0-based).

All Level 2 data products are affected by this anomaly.

Anomaly 2

Since May 11th, 2008 an anomaly is present in (cross-track) scenes 37-44 (0-based) towards the northern end of OMI orbit. The anomaly comprises a decrease or increase in the radiance signal depending on position in orbit.

On December 3rd, 2008, this anomaly expanded to cross-track position 44 (0-based) and along the full length of the orbit.

All Level 2 data products are affected by this anomaly.

Anomaly 3

Since January 24th, 2009 an anomaly is present in (cross-track) scenes 27-44 (0-based). The anomaly comprises a decrease and increase in the radiance signal depending on position in obit.

All Level 2 data products are affected by this anomaly.

Row Anomaly Flagging Overview

The flags for the row anomaly are stored in the Level 1B data product in the new field ‘XTrackQualityFlags’. When Level 2 products are generated, this field is copied in the Level 2 orbit data files. In addition, the Radiance Error bit or Radiance Warning bit in the Fit Quality flags of the Level 2 product are raised, depending on the status of the Level 1B corrections.

  • Anomaly 1: The Level 1B data has been flagged for this anomaly for (cross-track) scenes 53-54 (0-based). Level 2 data products have NOT been flagged at the moment.
  • Anomaly 2: The Level 1B data has NOT been flagged for this anomaly for (cross-track) scenes 37-44 at the moment. Level 2 data products have NOT been flagged at the moment.
  • Anomaly 3: The Level 1B data has NOT been flagged for this anomaly for (cross-track) scenes 27-44 at the moment. Level 2 data products have NOT been flagged at the moment.

 

Additional Notes

The OMI cross track positions mentioned here are 0-based and hold for UV2 and VIS channels only. For the UV1 channel all number should be divided by 2 and rounded to the nearest integer.

OMI flags are documented in the GDPS Input/Output Data Specification (IODS) (volume 2) of the Level 1B software, available from the NASA GES DISC: http://disc.sci.gsfc.nasa.gov/Aura/OMI/documents/v003/RD01_SD467_IODS_Vol_2_issue8.pdf

The flags for the row anomalies were implemented with version 1.1.2 of the Level 1B software that has been operational from October 8th, 2008. Version 1.1.3 has been operational from Feb 1, 2010.

 

For current OMI  Instrument status, visit

http://www.knmi.nl/omi/research/calibration/instrument_status_v3/index.html

Users are advised to read data quality documents available from the NASA GES DISC website and validation documents as provided.
 
 
 
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Last updated: Feb 01, 2016 10:36 AM ET
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