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SAFARI 2000 MODIS MOD04_L2 AEROSOL DATA, GRANT FORMAT, FOR SOUTHERN AFRICA
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Summary:

The subset of the Moderate Resolution Imaging Spectroradiometer (MODIS) MOD04_L2 aerosol product provided in this data set represents the swaths that coincide with known times of the South African Weather Bureau/Service (SAWS) Aerocommanders JRA and JRB research aircraft missions to support aerosol research and validation activities for the SAFARI 2000 region. The MODIS aerosol product monitors the ambient aerosol optical thickness over the oceans globally and over a portion of the continents. Further, the aerosol size distribution is derived over the oceans, and the aerosol type is derived over the continents. Daily Level 2 data are produced at the spatial resolution of a 10 x 10 1-km (at nadir) pixel array. The daily data files cover the period August 21, 2000, through September 26, 2000. For some data collection dates, there are two or more data files.

The MOD04_L2 swath data files included in this data set are from the GSFC DAAC (V4.1.0, Collection 004). The MODIS Level 2 data files were converted from Hierarchical Data Format (HDF) to granule tables (GRANT) format. The GRANT format provides the extracted Scientific Data Set (SDS) in ASCII table form where each pixel (x,y) is represented as a row of data with georeferencing information and each SDS is provided as a separate column in the table. The ASCII tables are in comma-delimited format and should be read with a text editor or spreadsheet software and not an image viewer.

Data Citation:

Cite this data set as follows:

Kaufman, Y. J., D. Tanré, and L. A. Remer. 2005. SAFARI 2000 MODIS MOD04_L2 Aerosol Data, GRANT Format, for Southern Africa. 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/813.

References:

Kaufman, Y. J. and D. Tanré. 1998. Algorithm for Remote Sensing of Tropospheric Aerosol from MODIS Products: MOD04_L2, MOD08_D3, MOD08_E3, MOD08_M3. ATBD Reference Number: ATBD-MOD-02. [ Document included as a companion file.]

Chu, D. A., Y. J. Kaufman, C. Ichoku, L. A. Remer, D. Tanré, and B. N Holben. 2002. Validation of MODIS aerosol optical depth retrieval over land. Geophys. Res. Lett., 10.1029/2001GL013205.

Ichoku, C., D. A. Chu, S. Mattoo, Y. J. Kaufman, L. A. Remer, D. Tanré, I. Slutsker, and B. Holben. 2002. A spatio-temporal approach for global validation and analysis of MODIS aerosol products. Geophys. Res. Lett. 10.1029/2001GL013206.

Remer, L. A., D. Tanré, Y. J. Kaufman, C. Ichoku, S. Mattoo, R. Levy, D. A. Chu, B. N. Holben, O. Dubovik, Z. Ahmad, A. Smirnov, J. V. Martins, and R. -R. Li. 2002. Validation of MODIS aerosol retrieval over ocean. Geophys. Res. Lett., 10.1029/2001GL013204.

Data Format:

The MOD04_L2 swath data files included in this data set are from the GSFC DAAC (V4.1.0, Collection 004). The MODIS Level 2 data files were converted from Hierarchical Data Format (HDF) to granule tables (GRANT) format. The GRANT format provides the extracted Scientific Data Set (SDS) in ASCII table form where each pixel (x,y) is represented as a row of data with georeferencing information and each SDS is provided as a separate column in the table. For information on missing data, see the companion file. The ASCII tables are in comma-delimited format and should be read with a text editor or spreadsheet software and not an image viewer.

The file naming convention is: MOD04_L2.AYYYYDDD.HHMM.grnt

Where: MOD04_L2 = MODIS product and level
A = Platform code (A= Terra)
YYYYDDD = Year and Julian day of acquisition
HHMM = Time of acquisition
.grnt = Suffix denoting GRANT-format data file

The typical structure of a GRANT file is given below, where the first several lines provide header information that precedes the data records.

line 1 Title MODIS Aerosol Products Granule Tables (GRANT)
line 2 HDF name Name of the original hdf file
line 3 SDS names Scientific Data Set names
line 4 SDS units Units for each SDS
line 5 SDS number of layers Number of layers
line 6 Geolocation #rows Size of the input image in lines (y, usually 203)
line 7 Geolocation #cols Size of the input image in samples (x, usually 135)
line 8 Pixel size (km) spatial resolution (10 km)
line 9-15 Contact Information Contact informaton for this product file
line 16 List of SDS extracted abbreviated names of extracted SDS (see table below)
line 17-->End of file pixel values, one line per pixel (row/column)

Column headings are as follows:

SDS Name SDS Short Name (column headings) Wavelength or other identifiers for multi-layer
SDS names (replaces '#' in the SDS short name)
Pixel Location rwo, column --
Longitude lon --
Latitude lat --
Solar_Zenith solz --
Solar_Azimuth sola --
Sensor_Zenith senz --
Sensor_Azimuth sena --
Scattering_Angle scang --
Optical_Depth_Land_And_Ocean AOT0550 --
Optical_Depth_Ratio_Small_Land_And_Ocean rAOTse0550 --
Continental_Optical_Depth_Land AOT####cont-l 0470, 0660
Corrected_Optical_Depth_Land AOT####corr-l 0470, 0550, 0660
Angstrom_Exponent_Land Aexp0470-0670-l --
Cloud_Fraction_Land cfrac-l --
Mean_Reflectance_Land mref####-l 0470, 0660, 0870, 2100, 3750
Solution_Index_Ocean_Small solindx-s#-o b, a (model fit values, b=best, a=average)
Solution_Index_Ocean_Large solindx-l#-o b, a (model fit values, b=best, a=average)
Effective_Optical_Depth_Average_Ocean AOT####ea-o 0470, 0550, 0660, 0870, 1200, 1600, 2100
Optical_Depth_Small_Average_Ocean AOT#####sa-o 0470, 0550, 0660, 0870, 1200, 1600, 2100
Effective_Radius_Ocean effr0550#-o b, a (model fit values, b=best, a=average)
Optical_Depth_Ratio_Small_Ocean_0.86micron rAOTse0860#-o b, a (model fit values, b=best, a=average)
Angstrom_Exponent_1_Ocean Aexp0550-0860#-o b, a (model fit values, b=best, a=average)
Angstrom_Exponent_2_Ocean Aexp0860-2130#-o b, a (model fit values, b=best, a=average)
Least_Squares_Error_Ocean lsqerr-#-o b, a (model fit values, b=best, a=average)
Cloud_Fraction_Ocean cfrac-o --
Backscattering_Ratio_Average_Ocean bsr####a-o 0470, 0550, 0660, 0870, 1200, 1600, 2100
Cloud_Condensation_Nuclei_Ocean CCN0550#-o b, a (model fit values, b=best, a=average)
Mean_Reflectance_Ocean mref####-o 0470, 0550, 0660, 0870, 1200, 1600, 2100
Mean_Reflectance_Land_All mrall####-l 0470, 0660, 2100
Standard Deviation_Reflectance_Land_All srall####-l 0470, 0660, 2100
Path_Radiance_Land pathrad####-l 0470, 0660
Error_Path_Radiance_Land errprad####-l 0470, 0660
Critical_Reflectance_Land critref####-l 0470, 0660
Error_Critical_Reflectance_Land errcref####-l 0470, 0660
QualityWeight_Path_Radiance_Land qwtprad####-l 0470, 0660
QualityWeight_Critical_Reflectance_Land qwtcref####-l 0470, 0660
Optical_Depth_by_models_ocean AOT0550m##-o 01, 02, 03, 04, 05, 06, 07, 08, 09

NOTE: There are 96 total columns for each data entry in the data files.

Additional information about the MODIS aerosol product, parameters measured, and data format is found in the companion file: ftp://daac.ornl.gov/data/safari2k/remote_sensing/modis_MOD04_aerosol/comp/modis_MOD04_aerosol_readme.pdf.

Document Information:

2005/8/1

Document Review Date:

2005/8/1

Document Curator:

webmaster@www.daac.ornl.gov

Document URL:

http://daac.ornl.gov