Abstract:
The OMI/Aura Level-2 Total Column Ozone Data Product OMTO3 (Version 003) is made available (http://disc.gsfc.nasa.gov/Aura/OMI/omto3_v003.shtml) from the NASA Goddard Earth Sciences Data and Information Services Center (GES DISC) for the public access.
The Ozone Monitoring Instrument (OMI)was launched aboard the EOS-Aura satellite on July 15, 2004(1:38 pm equator crossing time, ... ascending mode). OMI with its 2600 km viewing swath width provides almost daily global coverage. OMI is a contribution of the Netherlands Agency for Aerospace Programs (NIVR)in collaboration with Finish Meterological Institute (FMI), to the US EOS-Aura Mission. The principal investigator's (Dr. Pieternel Levelt) institute is the KNMI (Royal Netherlands Meteorological Institute). OMI is designed to monitor stratospheric and tropospheric ozone, clouds, aerosols and smoke from biomass burning, SO2 from volcanic eruptions, and key tropospheric pollutants (HCHO, NO2) and ozone depleting gases (OClO and BrO).
OMI sensor counts, calibrated and geolocated radiances, and all derived geophysical atmospheric products will be archived at the NASA Goddard DAAC.
OMI provides two Level-2 (OMTO3 and OMDOAO3) total column ozone products at pixel resolution (13 x 24 km at nadir) that are based on two different algorithms. This level-2 global total column ozone product (OMTO3)is based on the enhanced TOMS version-8 algorithm that essentially uses the ultraviolet radiance data at 317.5 and 331.2 nm. OMI additional hyper-spectral measurements help in the corrections for the factors that induce uncertainty in ozone retrieval (e.g., cloud and aerosol, sea-glint effects, profile shape sensitivity, SO2 and other trace gas contamination). In addition to the total ozone values this product also contains some auxiliary derived and ancillary input parameters including N-values, effective Lambertian scene-reflectivity, UV aerosol index, SO2 index, cloud fraction, cloud pressure, ozone below clouds, terrain height, geolocation, solar and satellite viewing angles, and extensive quality flags.
The shortname for this Level-2 OMI total column ozone product is OMTO3 and the algorithm lead for this product is NASA OMI scientist Dr. Pawan K. Bhartia ( Pawan.K.Bhartia@nasa.gov).
OMTO3 files are stored in EOS Hierarchical Data Format (HDF-EOS5). Each file contains data from the day lit portion of an orbit (~53 minutes). There are approximately 14 orbits per day. The maximum file size for the OMTO3 data product is about 35 Mbytes.
The OMTO3 data file contains one swath which consists of two groups:
Data fields: OMI Total Ozone,Effective Reflectivity (331 - 360 nm), N-value, Cloud Fraction, Cloud Top Pressure, O3 below Cloud, UV Aerosol Index, SO2 index, Wavelength used in the algorithm, many Auxiliary Algorithm Parameter and Quality Flags
Geolocation Fields: Latitude, Longitude, Time, Relative Azimuth, Solar Zenith and Azimuth, Viewing Zenith and Azimuth angles, Spacecraft Altitude, Latitude, Longitude, Terrain Height, Ground Pixel Quality Flags.
Description:
Near real-time (NRT) data are available from OMI for certain L2 and L3 products. Whereas the standard OMI forward processing acquires 2-hour L0 files from the GES DISC within 6-7 hours of real time, LANCE-OMI acquires session-based L0 files from EDOS and the end of the session is available within 10-30 minutes after real time.
Quality
The 'version 003' product is the second public release. The quality of this v003 product is based on improved calibration algorithm however this product is not fully validated yet. Please see below the detailed Quality assessment. Overall the quality of total ozone and AI data produced by OMTO3 is similar to that from TOMS. Based on experience with TOMS, the total ozone data provided in OMTO3 ... should have a root-mean squared error of 1-2%, depending on solar zenith angle, aerosol amount, and cloud cover. These errors are best described as pseudo-random: systematic over small areas with a unique geophysical regime, random over large areas contain mixture of geophysical regimes. Preliminary analyses show that OMTO3 data compare well with Dobson and Brewer stations. However for the most recent information on the OMTO3 data quality the data users are advised to see the data quality document available from the OMTO3 data product site(http://disc.gsfc.nasa.gov/Aura/OMI/omto3_v003.shtml).
Use Constraints
This Data set (version 003/second public release) is not fully validated yet. Before using it for any research please read the data quality document provided by the OMTO3 algorithm team and available from http://disc.gsfc.nasa.gov/Aura/OMI/omto3_v003.shtml
Ahmad, S. P., P. F. Levelt, P. K. Bhartia, E. Hilsenrath, G. W. Leppelmeier, and J. E. Johnson, Atmospheric Products from the Ozone Monitoring Instrument (OMI), Proceedings of SPIE conference on Earth Observing Systems VIII, San Diego, ... California, Aug 3-8, 2003. http://disc.sci.gsfc.nasa.gov/acdisc/ozone/docs/omi-spie-2003.doc
Bhartia, P. K. and C. W. Wellemeyer, OMI TOMS-V8 Total O3 Algorithm, Algorithm, Algorithm Theoretical Baseline Document: OMI Ozone Products, P. K. Bhartia (ed.), vol. II, ATBD-OMI-02, version 2.0, Aug. 2002. http://eospso.gsfc.nasa.gov/sites/default/files/atbd/ATBD-OMI-02.pdf
Brinksma, E. J., K. F. Boersma, and P. F. Levelt, OMI-Validation Requirements, May 16, 2003.
Froidevaux, L. and A. Douglass, Earth Observing System (EOS) Aura Science Data Validation Plan, July 2001
Levelt, P.F., J. P. Veefkind, R. H. M. Voors, and J. de Vries, Instrument Description, Algorithm Theoretical Baseline Document: OMI Instrument, Level 0 - 1B processor, Calibration Operations, P. F. Levelt (ed.), vol. I, ATBD-OMI-01, version 2, Aug. 2002.
Levelt, P. F., B. van den Oord, E. Hilsenrath, G. W. Leppelmeier, P. K. Bhartia, A. Malkki, H. Kelder, R. J. van der A, E. J. Brinksma, R. van Oss, P. Veefkind, M. van Weele, and R. Noordhoek, Science Objectives of EOS-Aura's Ozone Monitoring Instrument (OMI), Proc. Quad. Ozone Symposium, Sapporo, Japan, pp. 127-128, 2000.
Schoeberl, M.R., A.R. Douglass, E. Hilsenrath, P.K. Bhartia, J. Barnett, J. Gille, R. Beer, M. Gunson, J. Waters, P.F. Levelt, P. DeCola, The EOS Aura Mission, EOS, Transactions, American Geophysical Union 85 , Number 18, 4 May 2004. http://aura.gsfc.nasa.gov/project/eos-agu-aura-article.pdf
