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 MOD05_L2 water vapor product over seventeen (17) AERONET sunphotometer measurement sites in southern Africa for the period February 24, 2000, through March 4, 2002. The process of generating the statistics involves identifying these locations on the MODIS MOD05_L2 product and extracting the values of the pixel corresponding to each coordinate point as well as surrounding pixels falling within a 50 x 50 km box centered on the coordinate point.
The data product consists of column water vapor amounts. During the daytime a near-infrared algorithm is applied over clear land areas of the globe and above clouds over both land and ocean. Over clear ocean areas, water vapor estimates are provided over the extended glint area. An infrared algorithm for deriving atmospheric profiles is also applied both day and night for Level 2.
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 two variables: total column precipitable water vapor (infrared retrieved) and total column precipitable water vapor (near-infrared retrieved).
Cite this data set as follows:
Ichoku, C., Y. J. Kaufman, and L. A. Remer. 2005. SAFARI 2000 MAPSS MOD05_L2 Water Vapor 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/815.
Gao B. -C., and Y. J. Kaufman. 1998. The MODIS Near-IR Water Vapor Algorithm. Products: MOD05_L2, MOD08_D3, MOD08_E3, MOD08_M3. ATBD Reference Number: ATBD-MOD-03. [Document included as a companion file.]
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 two variables:
MOD05 Water Vapor Data File Name Data Column Abbrev. Definition Total Column Precipitable Water Vapor - Infrared Total Column Precipitable Water Vapor - Near-infrared
The data files contain the following columns:
The first 14 columns in each data file describe the AERONET location and measurement characteristics and the next 7 are computed statistics for the subset array of pixels for the AERONET location.
In the data files, column names representing the statistics are prefixed by: pval_, mean_, sdev_, slop_, slaz_, and mcoc_, respectively. These prefixes are followed by a short acronym to identify the water vapor product.
These statistical parameters were calculated for the MODIS MOD05 L2 water vapor product for SAFARI 2000 for the period February 24, 2000 through March 4, 2002. There may be some data gaps, however, 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 (29.220) SolarAzimuth
degrees (123.650) SensorZenith
degrees (20.840) SensorAzimuth
degrees (97.890) ScatteringAngle
degrees (missing) boxsize
Square km (11) nchan
Number of channels (1) pval_wir or _wni
Value of the central pixel in cm (3.583) npix_wir or _wni
Number of pixels in subset (94) mean_wir or _wni
Mean of the subset in cm (3.571) sdev_wir or _wni
Standard deviation of the subset in cm (0.159) slop_wir or _wni
Slope of a plane fitted to the subset (30.829) slaz_wir or _wni
Azimuth (direction, degrees from true north) of the slope (68.474) mcoc_wir or _wni
Multiple Correlation Coefficient (0.575)
Example data files: acsension_2002_wtr_vap_ir.csv
TITLE : MODIS Aerosol Products Subset Statistics (MAPSS)
PGE Type : MOD05_L2
SDS name : Water_Vapor_Infrared
SDS description : "Total Column Precipitable Water Vapor - IR Retrieval"
SDS no.of layers : 1
SDS units of measure : cm
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,SolarAzimuth,SensorZenith,SensorAzimuth,ScatteringAngle,boxsize,nchan,pval_wir,npix_wir,mean_wir,sdev_wir,slop_wir,slaz_wir,mcoc_wir
2002-01-02,11:15,0.46875000,MOD05_L2.A2002002.1115.003.2002007010715.hdf,Ascension_Island,-14.415,-7.976,29.220,123.650,20.840,97.890,,11,1,3.583,94,3.571,0.159,30.829,68.474,0.575
2002-01-02,23:30,0.97916669,MOD05_L2.A2002002.2330.003.2002007074817.hdf,Ascension_Island,-14.415,-7.976,142.440,-145.630,1.840,71.980,,11,1,,0,,,,,
2002-01-03,11:55,0.49652779,MOD05_L2.A2002003.1155.003.2002008224850.hdf,Ascension_Island,-14.415,-7.976,21.000,136.550,58.790,-83.050,,11,1,,68,3.942,0.129,16.447,17.914,0.398
2002-01-04,00:15,0.01041667,MOD05_L2.A2002004.0015.003.2002009234448.hdf,Ascension_Island,-14.415,-7.976,147.250,-160.260,64.630,-100.020,,11,1,,0,,,,,
2002-01-04,00:15,0.01041667,MOD05_L2.A2002004.0015.003.2002013202444.hdf,Ascension_Island,-14.415,-7.976,147.250,-160.260,64.630,-100.020,,11,1,,12,4.036,0.190,26.654,4.396,0.386
2002-01-04,11:00,0.45833334,MOD05_L2.A2002004.1100.003.2002010043926.hdf,Ascension_Island,-14.415,-7.976,31.940,120.800,43.360,98.670,,11,1,,0,,,,,
2002-01-04,11:00,0.45833334,MOD05_L2.A2002004.1100.003.2002014075343.hdf,Ascension_Island,-14.415,-7.976,31.940,120.800,43.360,98.670,,11,1,3.762,30,3.721,0.147,13.421,181.197,0.278
acsension_2002_wtr_vap_nir.csv
TITLE : MODIS Aerosol Products Subset Statistics (MAPSS)
PGE Type : MOD05_L2
SDS name : Water_Vapor_Near_Infrared
SDS description : "Total Column Precipitable Water Vapor - Near Infrared Retrieval"
SDS no.of layers : 1
SDS units of measure : cm
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,SolarAzimuth,SensorZenith,SensorAzimuth,ScatteringAngle,boxsize,nchan,pval_wni,npix_wni,mean_wni,sdev_wni,slop_wni,slaz_wni,mcoc_wni
2002-01-02,11:15,0.46875000,MOD05_L2.A2002002.1115.003.2002007010715.hdf,Ascension_Island,-14.415,-7.976,29.220,123.650,20.840,97.890,,51,1,2.522,1628,2.316,0.384,59.775,248.849,0.635
2002-01-02,23:30,0.97916669,MOD05_L2.A2002002.2330.003.2002007074817.hdf,Ascension_Island,-14.415,-7.976,142.440,-145.630,1.840,71.980,,51,1,,0,,,,,
2002-01-03,11:55,0.49652779,MOD05_L2.A2002003.1155.003.2002008224850.hdf,Ascension_Island,-14.415,-7.976,21.000,136.550,58.790,-83.050,,51,1,,1147,2.646,0.256,16.963,304.338,0.375
2002-01-04,00:15,0.01041667,MOD05_L2.A2002004.0015.003.2002009234448.hdf,Ascension_Island,-14.415,-7.976,147.250,-160.260,64.630,-100.020,,51,1,,0,,,,,
2002-01-04,00:15,0.01041667,MOD05_L2.A2002004.0015.003.2002013202444.hdf,Ascension_Island,-14.415,-7.976,147.250,-160.260,64.630,-100.020,,51,1,,0,,,,,
2002-01-04,11:00,0.45833334,MOD05_L2.A2002004.1100.003.2002010043926.hdf,Ascension_Island,-14.415,-7.976,31.940,120.800,43.360,98.670,,51,1,1.994,323,1.901,0.191,21.020,277.444,0.464
2002-01-04,11:00,0.45833334,MOD05_L2.A2002004.1100.003.2002014075343.hdf,Ascension_Island,-14.415,-7.976,31.940,120.800,43.360,98.670,,51,1,1.994,323,1.901,0.191,21.020,277.444,0.464
Additional information about the MODIS water vapor product, parameters measured, and data format is found in the companion file: http://daac.ornl.gov/daacdata/safari2k/remote_sensing/mapss_modis_watervapor/comp/mapss_modis_watervapor_readme.pdf.
2005/7/28
2005/7/28
webmaster@www.daac.ornl.gov