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.
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.
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.
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: http://daac.ornl.gov/daacdata/safari2k/remote_sensing/modis_MOD04_aerosol/comp/modis_MOD04_aerosol_readme.pdf.
2005/8/1
2005/8/1
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