Skip to main content

DAAC Home > Get Data > Field Campaigns > SAFARI 2000 (S2K) > Data Set Documentation
SAFARI 2000 MAPSS MOD05_L2 WATER VAPOR SUMMARY DATA FOR SOUTHERN AFRICA
Get Data

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 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).

Data Citation:

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.

References:

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.]

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 two variables:

MOD05 Water Vapor Data
File Name Data Column Abbrev. Definition
*_wtr_vap_ir
wir
Total Column Precipitable Water Vapor - Infrared
*_wtr_vap_nir
wni
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.

Document Information:

2005/7/28

Document Review Date:

2005/7/28

Document Curator:

webmaster@www.daac.ornl.gov

Document URL:

http://daac.ornl.gov