TROPOSPHERIC OZONE DATA FROM AURA OMI/MLS

MONTHLY-MEAN TROPOSPHERIC COLUMN OZONE (IN DOBSON UNITS):

September 2004, October 2004, November 2004

January 2005, February 2005, March 2005, April 2005, May 2005, June 2005, July 2005, August 2005, September 2005, October 2005, November 2005, December 2005

January 2006, February 2006, March 2006, April 2006, May 2006, June 2006, July 2006, August 2006, September 2006, October 2006, November 2006

MONTHLY-MEAN TROPOSPHERIC OZONE MEAN VOLUME MIXING RATIO (IN PPBV):

September 2004, October 2004, November 2004

January 2005, February 2005, March 2005, April 2005, May 2005, June 2005, July 2005, August 2005, September 2005, October 2005, November 2005, December 2005

January 2006, February 2006, March 2006, April 2006, May 2006, June 2006, July 2006, August 2006, September 2006, October 2006, November 2006

Here is an IDL reader for the above ASCII data files

The monthly mean data and IDL reader may also be downloaded using anonymous ftp:

> ftp jwocky.gsfc.nasa.gov

> Name: anonymous

> Password: (your email address)

> cd pub/ccd/data_monthly

> mget L3*

> get read_lvl3.pro

NOTES FOR THE MONTHLY MEAN DATA: OMI/MLS tropospheric ozone data were determined daily by subtracting MLS stratospheric column ozone from OMI total column ozone. Stratospheric column ozone from MLS was spatially interpolated (2D Gaussian/linear latitude-longitude interpolation) each day to fill in between the actual along-track measurements. The monthly means were then determined by averaging all available daily data within each month. The formatting of the data files is standard "GRIDTOMS" at 1 degree latitude by 1.25 degree longitude resolution. OMI total column ozone was filtered for near clear-sky conditions by including only measurements when coincident OMI reflectivity was less than 0.3. Mean ozone volume mixing ratio (in ppbv) was calculated each day from tropospheric column ozone (TCO, in Dobson Units) from 1270*TCO/(Psurface-Ptropopause) where surface pressure and tropopause pressure in the denominator are measured in hPa (same as millibar). Further details for the OMI/MLS method are discussed by Ziemke et al. [2006] (PDF file, 5.0 Mb)

DAILY TROPOSPHERIC OZONE "ALONG-TRACK" DATA:

Example image - June 23, 2006:

(click thumbnail
for large image)

Example image - October 15, 2006:

(click thumbnail
for large image)

The daily gridded "along-track" data and IDL reader may be
downloaded using anonymous ftp (Note: total disk space required is
about 120 Mbytes for either tropospheric column ozone or tropospheric
ozone mean volume mixing ratio):

> ftp jwocky.gsfc.nasa.gov

> Name: anonymous

> Password: (your email address)

> cd pub/ccd/data

> mget L3*

> get read_lvl3.pro

NOTES: The daily gridded tropospheric ozone data were determined using only "along-orbital track" measurements between OMI and MLS (see above example images). There was no attempt to use either interpolation or transport schemes to fill in MLS stratospheric column ozone between orbital tracks. The data (similar to the above monthly means) used National Centers for Environmental Prediction (NCEP) analyses and the World Meterological Organization (WMO) 2K per km vertical temperature gradient definition to determine tropopause pressure. These along-track measurements are referred to as being "co-located" regarding Aura OMI and MLS retrievals. The data correspond to ascending (south to north) daytime orbits where MLS makes a limb profile measurement in the direction of the Aura spacecraft orbital motion about 7 minutes prior to the total ozone measurement from OMI. The formatting of the data files is identical to the above monthly mean data files. The file naming for daily tropospheric column ozone goes as L3_tropo_ozone_column_YYYYMMDD_at, while for daily mean volume mixing ratio it goes as L3_tropo_ozone_vmr_YYYYMMDD_at. (YYYY refers to year, MM refers to month, and DD refers to day of the month.) Important note: The ASCII data files have been scaled to maximize information content given three numeric characters per value. Tropospheric column ozone (in Dobson Units) was multiplied by 10. Tropospheric mean volume mixing ratio (in ppbv) was multiplied by 5. The user may find these measurements useful for multi-year scientific analysis or as a stand-alone reference or "baseline" data set for comparing with tropospheric ozone from other sources (e.g., satellite, ground-based, models).

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