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     Absorbing Aerosol Index and residues from Metop-A/GOME-2
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     The following datasets are available:

../daily/data/20YY/YYMMDD.tar.gz, containing:

YYMMDD.egr

     ASCII file with gridded daily Metop-A/GOME-2 residues from the
     year 20YY, month MM, and day DD. The data in this ASCII file are
     in the format lon: 288 bins centered on 179.375 W to 179.375 E
     (1.25 degree steps); lat: 180 bins centered on 89.5 S to 89.5 N
     (1.00 degree steps), which is similar to the format used for the
     GOME AAI and the TOMS Nimbus-7 and Meteor-3 CD-ROM. Details of
     this format are explained in the EarthProbe Data Products User's
     Guide, "EARTHPROBE_USERGUIDE.PDF".

     The values are stored in 3-digit groups 111222333444. The numbers
     have been multiplied by 10 and 450 has been added. A value of 999
     is used for missing, bad, or flagged data.

     449 = -0.1    450 = 0.0    451 = 0.1

     999 = missing, bad, or flagged data.

------------------------------------------------------------------------

YYMMDD.n

     Number of values used for gridding in a box. Format similar to
     that of daily residue files, but numbers are not manipulated.

     The values are stored in 3-digit groups 111222333444.

------------------------------------------------------------------------

../monthly/data/YYMM.tar.gz, containing:

YYMM.ega

     ASCII file with gridded monthly averaged Metop-A/GOME-2 AAI from
     year 20YY and month MM. Format same as for daily residues.

     The values are stored in 3-digit groups 111222333444. The numbers
     have been multiplied by 10. A value of 999 is used for missing, bad,
     or flagged data, or to indicate that the AAI is not defined.

     1 = 0.1    100 = 10.0    998 = 99.8

     999 = missing, bad, or flagged data, or AAI not defined.

------------------------------------------------------------------------

YYMM.n

     Number of values used for gridding in a box. Format similar to
     that of monthly AAI files, but numbers are not manipulated.

     The values are stored in 3-digit groups 111222333444.

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     Some tools are available for handling and plotting the data in IDL:

../tools/readbin.pro

     READBIN, FILE, DATA, TITLE
     This procedure will read the data in the format described above
     from file FILE and return the 288 x 180 integer array DATA. TITLE
     is the string containing the text of the first line of the file.

------------------------------------------------------------------------

../tools/writebin.pro

     WRITEBIN, FILE, DATA, TITLE
     This procedure will store the data inside the 288 x 180 integer
     array DATA into the file FILE in the format described above. TITLE
     is the string containing the text of the first line of the file.

------------------------------------------------------------------------

../tools/plotgome.pro

     PLOTGOME
     This procedure will plot the data in the format described above
     from a selected file onto the world map. Uses readbin.pro.
     Type PLOTGOME, /HELP for more info on available keywords.

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     The following image files are available:

../daily/images/20YY/YYMMDD.gif

     Image files of the daily residue are available in GIF format.
     The files present the daily residue of year 20YY, month MM, and
     day DD projected onto the world map.

------------------------------------------------------------------------

../monthly/images/YYMM.gif

     Image files of the gridded monthly averaged AAI are available in
     GIF format. These files present the monthly averaged AAI of year
     20YY and month MM projected onto the world map.

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     References (follow the links on the webpage to download):

[1]  M. de Graaf, P. Stammes, O. Torres, and R.B.A. Koelemeijer,
     Absorbing Aerosol Index: Sensitivity analysis, application to
     GOME and comparison with TOMS, JGR 110, 2005.

[2]  L.G. Tilstra, O.N.E. Tuinder, and P. Stammes, GOME-2 Absorbing 
     Aerosol Index: Statistical analysis, comparison to GOME-1 and 
     impact of instrument degradation, EUMETSAT P.57, 2010.

[3]  L.G. Tilstra, M. de Graaf, O.N.E. Tuinder, R.J. van der A, and P. 
     Stammes, Studying trends in aerosol presence using the Absorbing 
     Aerosol Index derived from GOME-1, SCIAMACHY, and GOME-2, 
     EUMETSAT P.59, 2011.

[4]  M. de Graaf, O.N.E. Tuinder, and L.G. Tilstra, O3MSAF Algorithm 
     Theoretical Basis Document for ARS, O3MSAF/KNMI/ATBD/002, 2011.

[5]  O.N.E. Tuinder, O3MSAF Product User Manual for the ARS aerosol 
     products, O3MSAF/KNMI/PUM/002, 2011.

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