Nimbus7/TOMS July 1999 The data files in these subdirectories came from the Nimbus7/TOMS instrument and were generated by the TOMS science processing system at NASA/GSFC. The Version 7 dataset has a revised instrument calibration based on analysis of the entire 14.5 year data record, as well as an improved algorithm. Improvements in Version 7 from Version 6 include: 1) corrected 0.2 nm wavelength calibration error that caused a 3% absolute offset relative to Dobson 2) uses wavelength "triplets" that correct for errors linear in wavelength 3) improved ISCCP cloud height climatology, higher resolution terrain height maps 4) uses profile shape selectin to improve total ozone at very large solar zenith angles 5) more accurate radiative transfer in partial cloud scenes 6) improved a priori ozone climatology for table generation Data files: data/ozYYYY/gaYYMMDD.n7t (YYYY=1978-1993) These are gridded(g), ASCII (a) ozone data files from year YY, month MM, day DD. Details of this format are explained in the NIMBUS7_USERGUIDE.PDF, available in the parent directory of this path. Some format information is provided in ASCII file FORMAT.DOC in this directory. A Fortran stub program, RDGRID.FOR, for reading the ASCII gridded ozone, reflectivity, aerosol and uv data files is also provided in this directory. The values are in 3 digit groups 111222333444555 Sample value: 234 = 234 du 0 = fill value ---------------------------------------------------------------------------- data/reflYYYY/gaYYMMDD.n7r Reflectivity data, in format like that for ozone data. The values are in 3 digit groups 111222333444555 Sample value: _83 = 83% 999 = fill value --------------------------------------------------------------------------- data/a1YYYY/gaYYMMDD.n7a Aerosol data, in format like that for ozone data. The data are an aerosol index formed directly from the measured radiances in two TOMS channels. Positive values generally represent absorbing aerosols (dust and smoke) while negative values represent nonabsorbing aerosols. The identification is not perfect because of geophysical reasons (e.g., aerosol too low to the ground). The values are in 3 digit groups 111222333444555 The numbers have been multiplied by 10 --1 = 0.1 -11 = 1.1 111= 11.1 999 = missing or bad data -- stands for blanks References: Herman, J.R., P.K. Bhartia, O. Torres, C. Hsu, C. Seftor, E. Celarier, Global Distribution of UV-Absorbing Aerosols From Nimbus-7/TOMS Data, J. Geophys. Res., 102, 16, 911-16, 922, 1997. Torres, O., P.K. Bhartia, J.R. Herman, Z. Ahmad, and J. Gleason, Derivation of aerosol properties from satellite measurements of backscattered ultraviolet radiation: Theoretical basis, J. Geophys. Res., 103, 17099-17110, 1998. -------------------------------------------------------------------------- data/uvYYYY/gaYYMMDD.n7e Erythemal uv data. The files may be read with the format statements in RDGRID.FOR but see 1README.UV and erynotes.pdf for interpretation/decoding information. The values are in 3 digit groups 111222333444555 123 = 2.3x10^1 J/m2 -23 = 2.3 --3 = 0.3 999 = missing or bad data ........................................................................... data/monthly_averages/ozone/gmYYMM.n7t This directory contains gridded monthly (gm) average datasets from year YY and month MM. At least 20 days of data must be available for a monthly average to be considered valid. Monthly average data for aerosol, UV and reflectivity are also provided in directories located in a path structure similar to that for ozone. The Fortran statements that wrote the data records of these monthly files are: DO 570 IL=1,180 DO 560 jj=1,288 560 OZONE(JJ)=ozav(JJ,IL) write(21,'(1X,25I3)') (OZONE(jj),jj=1,275) write(21,'(1X,13I3,1A17)') (OZONE(jj),jj=276,288), latlab(IL) 570 CONTINUE ............................................................................ data/overpass/OVPxxx.n7t These files contain a subset (seconds UT, latitude, longitude, total ozone, surface reflectivity, solar zenith angle, aerosol index, SOI index, etc.) of Nimbus7 data specific to a particular latitude-longitude location. xxx designates a numerical site location as listed in ASCII file "1Sitelist" in this directory. Fortran statements that can be used to read the 1st header record and the data records in the OVPxxx files are the following: For the header record: CHARACTER*28 site_name INTEGER*4 site_id, site_alt REAL*4 site_lat, site_lon Read(lun,2) site_name, site_id, site_lat,site_lon, site_alt 2 Format(A30,4X,I3,7X,F7.2,7X,F7.2,7X,I4) and for the data records: Format(F7.1,1X,I4,1X,I3,1X,I5,2X,I2,1X,F6.2,1X,F7.2,1X, I3,1X,I3,1X,F5.2,1X,F5.1,1X,F5.1,1X,F6.2,1X,I4) /overpass/1README provides more information about the OVPxxx files. .......................................................................... data/zonal_means/ozone/zm_month.n7t and zmday_YY.n7t (YY=1978 to 1993) This directory contains zonal mean averages of the version 7 Nimbus 7 TOMS ozone data. The monthly zonal means are in the file zm_month.n7t, while the daily zonal means are in files named for each year - for example: zmday_79.n7t. The averages are for 5 degree latitude zones, area weighted. At least 75% of possible data in a given zone must be present for the mean to be calculated. In 1978 and 1979 there were missing days (6 missing in 1978, 29 missing in 1979) when the TOMS instrument was turned off to conserve power. In the later years there are at least some data every day. Zonal means for aerosol, UV and reflectivity are also provided in directories located in a path structure similar to that for ozone. The Fortran statements that wrote the header and data records of file zm_month are the following: CHARACTER*69 MONLAB Data MONLAB/'Jan Feb Mar Apr May Jun Jul Aug Sep & Oct Nov Dec'/ do 20 j=1,37 lat(j)=-95 + 5*j 20 continue write(22,'(8x,A69)') MONLAB DO 300 IZ=1,36 write(22,'(I3,I4,12f6.1)') lat(IZ),lat(IZ+1),(ozm(IM,IZ),IM=1,12) 300 CONTINUE write(22,'(I3,I4,12f6.1)') -65,0,(ozm(IM,37),IM=1,12) write(22,'(I3,I4,12f6.1)') 0,65,(ozm(IM,38),IM=1,12) write(22,'(I3,I4,12f6.1)') -65,65,(ozm(IM,39),IM=1,12) The Fortran statement that wrote the data records of the zmday_YY files is: write(21,'(A12,F9.3,1X,36F6.1,3X,3F6.1)') date,yd,zmd ......................................................................... If these data are downloaded and used in publication, please give proper credit to NASA/GSFC TOMS Ozone Processing Team. For more information about the Version 7 Nimbus-7/TOMS dataset, contact Dr. Richard D. McPeters Code 916 NASA Goddard Space Flight Center Greenbelt, MD 20771 mcpeters@wrabbit.gsfc.nasa.gov