Daily Aerosol Index (AI) data from Earth Probe (EP) Total Ozone Mapping Spectrometer (TOMS) for the period of August 12-September 30, 2000, were processed and provided by the Atmospheric Chemistry and Dynamics Branch at NASA/GSFC for the SAFARI 2000 Dry Season Aircraft Campaign.
The TOMS AI is formed directly from measured TOMS radiances in two channels. It is a measure of how much the wavelength dependence of backscattered UV radiation from an atmosphere containing aerosols (Mie scattering, Rayleigh scattering, and absorption) differs from that of a pure molecular atmosphere (pure Rayleigh scattering). Quantitatively, the AI is defined at http://toms.gsfc.nasa.gov/aerosols/AI_definition/ai_ep_definition.pdf. Positive values represent absorbing aerosols (dust and smoke); negative values represent non-absorbing aerosols. The identification is not perfect because of geophysical reasons (e.g., when aerosols are at a low altitude).
The data from TOMS records have been used increasingly to understand the behavior of aerosols within the atmosphere. The TOMS is the first instrument to allow observation of aerosols as the particles cross the land/sea boundary. Using these data it is possible to observe a wide range of phenomena such as desert dust storms, forest fires, and biomass burning.
The TOMS AI data are a daily gridded Level-3 product (ASCII .dat format) that covers the area of 40 deg. S to the Equator and 40 deg. W to 80 deg. E. There is also a JPEG image of each data file.
Cite this data set as follows:
McPeters, R., A. M. Thompson, and D. Larko. 2005. SAFARI 2000 TOMS Aerosol Index Data, Southern Africa, Dry Season 2000. Data set. Available on-line [http://daac.ornl.gov/] from Oak Ridge National Laboratory Distributed Active Archive Center, Oak Ridge, Tennessee, U.S.A. doi:10.3334/ORNLDAAC/823.
Herman, J. R., P. K. Bhartia, O. Torres, C. Hsu, C. Seftor and E. Celarier. 1997. Global distribution of uv-absorbing aerosols from Nimbus 7/TOMS data. J. Geophys. Res., 102: 16,911-16,922.
Torres, O., P. K. Bhartia, J. R. Herman, Z. Ahmad, and J. Gleason. 1998. Derivation of aerosol properties from satellite measurements of backscattered ultraviolet radiation: Theoretical basis. J. Geophys. Res., 103: 17099-17110.
Daily Aerosol Index gridded ASCII data files from EP TOMS contain format information in the header of each file. There is a separate file for each day of data collection. There is also a JPEG image of each data file.
Each value is 3 characters long (e.g., 111222333444555). The Aerosol Index has been multiplied by 10.
Positive values represent absorbing aerosols (dust and smoke).
Negative values represent non-absorbing aerosols. The explicit negative sign is included in the character count.
999 = missing or bad data.
Blank spaces are considered characters.
For example:
(blank)(blank)1=0.1 AI
(blank)11=1.1 AI
111=11.1 AI
For instance, the first data row in the Sample Data File below would resolve to:
-8 -9 -9 -7-12-10-11 ...
-0.8,-0.9,-0.9,-0.7,-1.2,-1.0,-1.1 ...
Data Users Please Note:
In all data files, the first data value corresponds to a location centered at 39.5 S, 39.375 W.
In all data files, the last data value corresponds to a location centered at 0.5 S, 79.375 E.
Sample TOMS Aerosol Index Data File
August 12, 2000 Near Realtime Version 7 EP TOMS AEROSOL INDEX X 10 Longitudes: 96 bins centered on 39.375 W to 79.375 E (1.25 degree steps) Latitudes : 40 bins centered on 39.5 S to 0.5 S (1.00 degree steps) -8 -9 -9 -7-12-10-11 -8 -4 -9 -9 -9 -9 -3 -7 -2 0 0 -4 -6 -4 -6 -7 -7 -8 -9-10 -7 -4 -6 -6 -6 -8 -4 -3 -5 -5 -8 -7 -7 -9 -7 -9 -9-11-10-11 -9-10 -7 -7 -5 -7 -5 -4 -6 -3 -8 0 -6 -8 -9 -5 -8 -9 -6 -9 -7-11-11 -8 -3 -4 3 -1 -1 -1 0 -3 -3 -4-10-13 -8-11-11 -9 -8-10 -7 -7 -6 -6 -4 -2 0 lat = -39.5 -7-11-11 -8-11 -7 -9 -6 -8 -7 -6-10 -7 -1 -7 0 0 -2 -7 -5 -7 -5 -6 -9 -7 -6 -3 -4-11 -8 -5 -1 -2 -2 0 1 -1 -5 -9 -6 -6 -5 -6 -9 -9 -7 -9 -9 -8 -8 -10 -8 -7 -5 0 -8 -4 -4 -5 -4 -6 -5 -5 -7-12 -9 -8-11-11 -8 -1 -3 -1 0 -3 -3 -5 -1 0 -3-13-10 -8-10-10-11 -7-11 -8 -8 -7 -8 -8 -7 -2 -4 lat = -38.5 -8-12 -6-10 -8 -8-11 -9-10-10-10 -3 -6 -7 -7 -2 -4 -5 -6 -5 -5 -6 -6 -5 -3 -6 -9-11-14 -7 -7 -4 -1 0 1 -5 -7 -5 -5 -6 -6 -5 -7-13-12-10 -8-10-11 -8 -7 -7 -6 -7 -6 -5 -5 -7 -8 -9 -8 -8 -5 -9-10 -8-10-10 -5 -8 -5 1 -5 -4 -5 -4 -4 0 0 -2-14 -9 -9-10 -9 -7 -8-11 -6 -9 -8 -7 -6 -3 -3 -1 lat = -37.5 -7 -6-10-11-12-11-11-11-11 -7 -6 -6 -6 -3 -3 -4 -4 -5 -5 -5 -7 -5 -3 -2 -6 -10 -9-10 -8 -6 -4 -2 -2 -1 1 -6 -5 -9-11-11-13-10-12 -9 -7 -8-12-12-11-10 -11-10-10-10-10 -5 -7 -7 -8 -9 -7 -7 -8-10 -7 -7 -7 -5-10 -8 0 -1 -8 -4 -1 -11 -6 -1 -1 -5 -7-11 -8 -9 -7 -6 -8 -7 -7 -7 -8 -4 -1 -4 0 -3 lat = -36.5 |
Additional information about the data format and parameters measured is found in the companion file: http://daac.ornl.gov/daacdata/safari2k/remote_sensing/TOMS_aerosol/comp/TOMS_aerosol_readme.pdf. Also see the TOMS Users Guide: http://daac.ornl.gov/daacdata/safari2k/remote_sensing/TOMS_aerosol/comp/EARTHPROBE_USERGUIDE.pdf.
2005/7/19
2005/7/19
webmaster@www.daac.ornl.gov