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SAFARI 2000 MAPSS MOD04_L2 AEROSOL SUMMARY DATA FOR SOUTHERN AFRICA
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Summary:

The Moderate Resolution Imaging Spectroradiometer (MODIS) Atmosphere Group develops remote-sensing algorithms for deriving sets of atmospheric parameters from MODIS radiance data. These parameters can be integrated into conceptual and predictive global models. MODIS Atmosphere Products Subset Statistics (MAPSS) are generated over important locations around the world as one of the ways to increase the scope of application of the MODIS atmospheric parameters.

This MAPSS data set contains daily time series of the MODIS MOD04_L2 aerosol product over seventeen (17) AERONET sunphotometer measurement sites in southern Africa for the period February 26, 2000, through December 31, 2001. The process of generating the statistics involves identifying these locations on the MODIS MOD04_L2 product and extracting the values of the pixel corresponding to each coordinate point as well as values for surrounding pixels falling within a 50 x 50 km box centered on the coordinate point.

The data files are stored as ASCII tables in comma-separated-value (.csv) format. There is one file per site per year for each of the following variables: cloud fraction (land); cloud fraction (ocean); particle effective radius (ocean); optical depth (land and ocean); optical depth (land, corrected); optical depth (ocean, effective average); and optical depth ratio (small ocean).

Data Citation:

Cite this data set as follows:

Ichoku, C., Y. Kaufman, and L. Remer. 2005. SAFARI 2000 MAPSS MOD04_L2 Aerosol Summary Data 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/814.

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. [ http://modis.gsfc.nasa.gov/data/atbd/atbd_mod02.pdf ]

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 data files are stored as ASCII tables in comma-separated-value (.csv) format. There is one file per site per year for each of the following seven variables:

MOD04 Aerosol Data
File Name Data Column Abbreviations Definition
cld_frc_lan cfrac-l cloud fraction land
cld_frc_ocn cfrac-o cloud fraction ocean
eff_rad_ocn effr0550b-a, effr0550b-o effective radius ocean
opt_dp_l-o AOT0550 optical depth land and ocean
opt_dp_lan_c AOT0470corr-l, AOT0550corr-l,
AOT0660corr-l
optical depth land, corrected
opt_dp_ocn_e AOT0470ea-o, AOT0550ea-o,
AOT0660ea-o, AOT0870ea-o,
AOT1200ea-o, AOT1600ea-o,
AOT2100ea-o
optical depth ocean, effective average
opt_dp_s_ocn rAOTse0550a, rAOTse0550b optical depth ratio small ocean

The data files contain the following columns:

In the data files column names representing the above statistics are prefixed by: pval_, mean_, sdev_, slop_, slaz_, and mcoc_, respectively. These prefixes are followed by a short acronym designating the aerosol product. If numbers or number ranges are included in these acronyms, they represent wavelength in nanometers. If the acronym ends with a "-l", then the product covers only land surfaces, but if it ends with a "-o" the product covers only ocean surfaces. Otherwise, it can potentially cover any type of surface.

These statistical parameters were calculated for the MODIS MOD04_L2 aerosol product for SAFARI 2000 for the period February 26, 2000, through December 31, 2001. However, there may be some data gaps resulting from non-retrieval of the MODIS images due to some unfavorable factors such as cloud cover in the reflective wavebands.

NOTE: It is possible for the data columns to change part way through a file as parameters were added or removed from the extraction process. Instead of reprocessing the entire file, such changes were marked by the insertion of a new list of column headings at the start of the new column arrangement.

Column Label Description/format  (example)

Date

2002-01-02

Time

11:15

Dayfrac

0.46875000

HDFfile

MOD05_L2.A2002002.1115.003.2002007010715.hdf

Location

Ascension_Island

Longitude

decimal degrees  (-14.415)

Latitude

decimal degrees  (-7.976)

SolarZenith

degrees 

SolarAzimuth

degrees 

SensorZenith

degrees 

SensorAzimuth

degrees 

ScatteringAngle

degrees 

boxsize

Square km 

nchan

Number of channels 

pval_*

Value of the central pixel, units given in file header 

npix_*

Number of pixels in subset

mean_*

Mean of the subset, units given in file header 

sdev_*

Standard deviation of the subset, units given in file header 

slop_*

Slope of a plane fitted to the subset 

slaz_*

Azimuth (direction, degrees from true north) of the slope 

mcoc_*

Multiple Correlation Coefficient 

* See "Data Column Abbreviations" in previous table.

Example data files:ascension_2000_cld_frc_lan.csv

TITLE : MODIS Aerosol Products Subset Statistics (MAPSS)

PGE Type : MOD04_L2

SDS name : Cloud_Fraction_Land

SDS description : "Cloud fraction (%)"

SDS no.of layers : 1

SDS units of measure : None

Contact person : Charles Ichoku (ichoku@climate.gsfc.nasa.gov)

Pr. Investigator(s) : Yoram Kaufman (kaufman@climate.gsfc.nasa.gov)

Lorraine Remer (remer@climate.gsfc.nasa.gov)

Date,Time,Dayfrac,HDFfile,Location,Longitude,Latitude,SolarZenith,SensorZenith,ScatteringAngle,boxsize,nchan,pval_cfrac-l,npix_cfrac-l,mean_cfrac-l,sdev_cfrac-l,slop_cfrac-l,slaz_cfrac-l,mcoc_cfrac-l

2000-02-28,11:40,0.48611113,MOD04_L2.A2000059.1140.002.2000062220536.hdf,Ascension_Island,-14.415,-7.976,22.090,7.830,157.840,3,1,,0,,,,,

2000-03-01,11:25,0.47569445,MOD04_L2.A2000061.1125.002.2000067110824.hdf,Ascension_Island,-14.415,-7.976,25.040,21.140,149.920,3,1,,0,,,,,

2000-03-02,12:10,0.50694448,MOD04_L2.A2000062.1210.002.2000069055534.hdf,Ascension_Island,-14.415,-7.976,14.340,58.460,122.240,3,1,,0,,,,,

2000-03-05,11:00,0.45833334,MOD04_L2.A2000065.1100.002.2000070072347.hdf,Ascension_Island,-14.415,-7.976,31.080,58.090,123.540,3,1,,0,,,,,

ascension_2000_eff_rad_ocn.csv

TITLE : MODIS Aerosol Products Subset Statistics (MAPSS)

PGE Type : MOD04_L2

SDS name : Effective_Radius_Ocean

SDS description : "Effective_Radius at 0.55 micron of both solutions"

SDS no.of layers : 2

SDS units of measure : micron

Contact person : Charles Ichoku (ichoku@climate.gsfc.nasa.gov)

Pr. Investigator(s) : Yoram Kaufman (kaufman@climate.gsfc.nasa.gov)

Lorraine Remer (remer@climate.gsfc.nasa.gov)

Date,Time,Dayfrac,HDFfile,Location,Longitude,Latitude,SolarZenith,SensorZenith,ScatteringAngle,boxsize,nchan,pval_effr0550b-o,npix_effr0550b-o,mean_effr0550b-o,sdev_effr0550b-o,slop_effr0550b-o,slaz_effr0550b-o,mcoc_effr0550b-o,pval_effr0550a-o,npix_effr0550a-o,mean_effr0550a-o,sdev_effr0550a-o,slop_effr0550a-o,slaz_effr0550a-o,mcoc_effr0550a-o

2000-02-28,11:40,0.48611113,MOD04_L2.A2000059.1140.002.2000062220536.hdf,Ascension_Island,-14.415,-7.976,22.090,7.830,157.840,3,2,,0,,,,,,,0,,,,,

2000-03-01,11:25,0.47569445,MOD04_L2.A2000061.1125.002.2000067110824.hdf,Ascension_Island,-14.415,-7.976,25.040,21.140,149.920,3,2,,0,,,,,,,0,,,,,

2000-03-02,12:10,0.50694448,MOD04_L2.A2000062.1210.002.2000069055534.hdf,Ascension_Island,-14.415,-7.976,14.340,58.460,122.240,3,2,,4,0.633,0.550,65.426,123.469,1.000,,4,1.121,0.092,42.253,166.752,0.909

2000-03-05,11:00,0.45833334,MOD04_L2.A2000065.1100.002.2000070072347.hdf,Ascension_Island,-14.415,-7.976,31.080,58.090,123.540,3,2,,0,,,,,,,0,,,,,

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/mapss_modis_aerosol/comp/mapss_modis_aerosol_readme.pdf.

Document Information:

2005/7/27

Document Review Date:

2005/7/27

Document Curator:

webmaster@www.daac.ornl.gov

Document URL:

http://daac.ornl.gov