________________________________________________________________________ Absorbing Aerosol Index and residues from ERS-2/GOME ________________________________________________________________________ The following datasets are available: ../daily/data/**YY/YYMMDD.tar.gz, containing: YYMMDD.egr ASCII file with gridded daily ERS-2/GOME residues from year **YY, 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 SCIAMACHY 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 ERS-2/GOME AAI from year **YY 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. ------------------------------------------------------------------------ ../daily/lv2data/**YY/YYMMDD_gome_aai.tar.gz, containing: YYMMDD_HHMM_gome_sc.aai ASCII files with ERS-2/GOME level-2 residue data for each of the orbits from year **YY, month MM, and day DD. The HH and MM relate to the time of first measurement of the particular orbit. Residue, time, and geolocation information are given in the files. A tool to extract the data in IDL exists and can be downloaded. ________________________________________________________________________ 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/read_aai_level2.pro READ_AAI_LEVEL2 This procedure will read level-2 AAI data. See the source code for the calling sequence and the list of returned parameters. ------------------------------------------------------------------------ ../tools/plot_bin.pro PLOT_BIN This procedure will plot the data in the format described above from a selected file onto the world map. Uses readbin.pro. Type PLOT_BIN, /HELP for more info on available keywords. ________________________________________________________________________ The following image files are available: ../daily/images/**YY/YYMMDD.gif Image files of the daily residue are available in GIF format. The files present the daily residue of year **YY, 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 **YY and month MM projected onto the world map. ________________________________________________________________________ Daily log files are available for each processed day: ../daily/logs/**YY/YYMMDD.log These files contain all processing information. Log files are also available for days where no GOME data were available. ________________________________________________________________________ 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, 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. ________________________________________________________________________