This data set includes data collected over the Soil Moisture Experiment 2002 (SMEX02) area of Iowa, USA, during June and August, 2002. The SeaWinds scatterometer on NASA's QuikScat satellite collected backscatter data. Data are provided in binary arrays, digital images, and video (.avi) files, and are available via FTP.
These data were collected as part of a validation study for the Advanced Microwave Scanning Radiometer - Earth Observing System (AMSR-E). AMSR-E is a mission instrument launched aboard NASA's Aqua Satellite on 04 May 2002. AMSR-E validation studies linked to SMEX are designed to evaluate the accuracy of AMSR-E soil moisture data. Specific validation objectives include assessing and refining soil moisture algorithm performance; verifying soil moisture estimation accuracy; investigating the effects of vegetation, surface temperature, topography, and soil texture on soil moisture accuracy; and determining the regions that are useful for AMSR-E soil moisture measurements.
Nghiem, S. 2004. SMEX02 QuikSCAT/SeaWinds Backscatter Data, Iowa. Boulder, CO, USA: National Snow and Ice Data Center. Digital media.
|Data format||Binary, browse image, and video files|
|Spatial coverage and resolution||39° to 45°N, -98° to -89°W
25 km resolution
|Temporal coverage and resolution||Daily coverage 1 June through 21 August 2002|
|File naming convention||Binary data files are named using the following format:
Year, month, day, polarization (H or V), version, ascending or descending.bin
For example: 20020828Hc5des.bin
See below for details and other data file naming conventions
|File size||Binary files are 6 KB
browse image files are 24.8-57.2 KB
video files are 68.9-74.6 MB
|Procedures for obtaining data||Data are available via FTP.|
Son V. Nghiem
Jet Propulsion Laboratory
California Institute of Technology
NSIDC User Services
National Snow and Ice Data Center
CIRES, 449 UCB
University of Colorado
Boulder, CO 80309-0449 USA
phone: +1 303.492.6199
fax: +1 303.492.2468
form: Contact NSIDC User Services
Data are binary arrays, browse image files, and video files.
The following table shows the directories and contents of the directories.
|data||All binary data files|
|images/polarization and direction directories||Four browse images per day, with names that indicate polarization and direction|
|movies||AVI movies made from the images in the images directory|
|reader||Fortran reader to read data files|
The fields in the binary file names are as follows:
For example, the data in the file "20020828Hc5des.bin" were obtained 28 August 2002 at a horizontal polarization and a descending pass.
The browse image files have a complex naming convention, explained by the following table. The field descriptions use examples from the file "20020609_1602Hc5des.gif."
The video files follow this convention:
For example, "qscat_v_pol_ascending.avi."
Each binary data file is 6 KB, image files are 24.8-57.2 KB, and video files are 68.9-74.6 MB.
Southernmost Latitude: 39° N
Northernmost Latitude: 45° N
Westernmost Longitude: -98° W
Easternmost Longitude: -89° W
Measurements are in 25 km resolution.
Data are gridded in 0.2 degrees in latitude/longitude projection.
Data cover the period of 1 June through 21 August 2002.
Daily coverage includes four browse images per day. Images include ascending and descending images for both horizontal (H) and vertical (V) polarizations.
The parameter for this data set is microwave backscatter. The following chart shows the backscatter data for the SMEX02 study period. (Click on the image to see a larger version of the chart.)
Backscatter measurements are given in decibels (dB).
The following image is a portion of the binary data file "20020831_Vc5des.bin."
The next image is a small version of the image file "20020827_1502Vc5des.gif."
Data are available via FTP.
Total volume of the binary, image, and movie files is 603.63 MB.
A Fortran reader is available for download with the binary data files. The Fortran code was written in Fortran77 and tested using a Sun compiler. You can also view the data with other appropriate applications.
See Soil Moisture Experiment (SMEX) for more information.
The QuikSCAT satellite was successfully launched at 7:15 p.m. Pacific Daylight Time on 19 June 1999 from the Vandenberg Air Force Base in California. The satellite carries the SeaWinds scatterometer for ocean wind measurements. SeaWinds uses a rotating dish antenna with two spot beams that sweep in a circular pattern. The antenna radiates microwave pulses at a frequency of 13.4 GHz across broad regions on Earth's surface. The scatterometer collects data at 13.4 GHz on both ocean and land. Backscatter data, at a radiometric resolution of 7 km x 25 km, are acquired with the vertical polarization at a constant incidence angle of 54° over a conical-scanning swath of 1800 km, and with the horizontal polarization at 46° over a 1400-km swath. The large swath can cover almost the entire globe in two days even at low latitudes and equatorial regions.
The cell sigma0 data were grouped by day, local time of day, beam, and geographic location. Data quality flags were checked. Only data passing the quality check were used. The average sigma0 was calculated for each group using natural numbers, not dB.
S. V. Nghiem and G. Neumann. 2004. "QuikSCAT/SeaWinds Data Package for SMEX 2002." JPL CL 04-0432, Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California.
SeaWinds at JPL
The following acronyms and abbreviations are used in this document.
|AMSR-E||Advanced Microwave Scanning Radiometer - Earth Observing System|
|AVI||Audio-Visual Interleave (video format)|
|FTP||File Transfer Protocol|
|GIF||Graphics Interchange Format|
|JPL||Jet Propulsion Laboratory|
|SMEX||Soil Moisture Experiment|