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Data Set ID:

SMEX02 AMSR-E Level 3 Daily Gridded Brightness Temperatures, Iowa, Version 1

This data set contains Advanced Microwave Scanning Radiometer - Earth Observing System (AMSR-E) level 3 daily gridded brightness temperatures, spatially subsetted to the state of Iowa, USA.

Geographic Coverage

  • Microwave > Brightness Temperature
Spatial Coverage:
  • N: 45, S: 39, E: -89, W: -98

Spatial Resolution: Not Specified
Temporal Coverage:
  • 1 June 2002 to 31 August 2002
Temporal Resolution: Not specified
Data Format(s):
  • Binary
  • ASCII Text
Platform(s) AQUA
Sensor(s): AMSR-E
Version: V1
Data Contributor(s): Eni Njoku
Data Citation

As a condition of using these data, you must cite the use of this data set using the following citation. For more information, see our Use and Copyright Web page.

Njoku, E. G. 2004. SMEX02 AMSR-E Level 3 Daily Gridded Brightness Temperatures, Iowa, Version 1. [Indicate subset used]. Boulder, Colorado USA. NASA National Snow and Ice Data Center Distributed Active Archive Center. doi: [Date Accessed].

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Detailed Data Description


The latitude and longitude data are ASCII files. Each daily brightness temperature file contains 24 data arrays of dimension 24 x 35 (rows/latitudes x columns/longitudes). The data are stored as two-byte, big-endian integers in column major order, where following along the stored contiguous data increases rows before columns. Data arrays are from the 6.9, 10.7, 18.7, 36.5, and 89.0 GHz channels (V and H). The order and spatial resolution of the 24 data arrays are shown in the following table.

Channel Type Resolution
TB06.9V Ascending 56 km
TB06.9H Ascending 56 km
TB10.7V Ascending 56 km
TB10.7H Ascending 56 km
TB18.7V Ascending 56 km
TB18.7H Ascending 56 km
TB36.5V Ascending 56 km
TB36.5H Ascending 56 km
TB36.5V Ascending 12 km
TB36.5H Ascending 12 km
TB89.0V Ascending 12 km
TB89.0H Ascending 12 km
TB06.9V Descending 56 km
TB06.9H Descending 56 km
TB10.7V Descending 56 km
TB10.7H Descending 56 km
TB18.7V Descending 56 km
TB18.7H Descending 56 km
TB36.5V Descending 56 km
TB36.5H Descending 56 km
TB36.5V Descending 12 km
TB36.5H Descending 12 km
TB89.0V Descending 12 km
TB89.0H Descending 12 km
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File Naming Convention

Brightness temperature data file names use the following convention:
  X1 = version number of the level 3 data
  YYYY = four-digit year
  MM = two-digit month
  DD = two-digit day

Latitude and longitude files are named "Iowa_lat.txt" and "Iowa_lon.txt".

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File Size

Binary files are 40 KB each. Longitude and latitude files are 14 KB.

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Binary files are 40 KB each. Longitude and latitude files are 14 KB. Total volume is 3.2 MB.

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Spatial Coverage

The study area covers the state of Iowa in the United States.

Southernmost Latitude: 39 ° N 
Northernmost Latitude: 45° N 
Westernmost Longitude: -98° W
Easternmost Longitude: -89° W

Spatial Resolution

Each daily brightness temperature file contains data arrays from the 6.9, 10.7, 18.7, 36.5, and 89.0 GHz channels (V and H). The resolution is either 56 km or 12 km. The 6.9, 10.7, and 18.7 (V and H) data are 56 km resolution; the 89.0 GHz (V and H) data are 12 km resolution. The 36.5 GHz (V and H) data are provided with both 56 km and 12 km resolution. (Refer to the channel table in the Format section of this document.)

The 56 km and 12 km resolutions correspond to the Resolution 1 and Resolution 4 definitions contained in the AMSR-E/Aqua L2A Global Swath Spatially-Resampled Brightness Temperatures (Tb) documentation under Spatial Resolution.


The data are in 25 km cylindrical EASE-Grid projection. Please see Processing Steps for details.

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Temporal Coverage

The study was conducted 1 June through 31 August 2002.

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Parameter or Variable

Parameter Description

This data set contains AMSR-E level 3 daily gridded brightness temperatures.

Unit of Measurement

Brightness temperatures are given in tenths Kelvin.

Parameter Values

The brightness temperature data values are in units of tenths Kelvin, and are written as two-byte integers. The data arrays are written sequentially in flat binary format on a big-endian UNIX machine.

Sample Images

The following sample images illustrate the 36.5 GHz (V) data in 56 km and 12 km resolution. Click on a thumbnail below to view the full image.

56 km Sample 12 km Sample
Click to view 56 km sample image Click to view 12 km sample image
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Software and Tools

The following MATLAB code illustrates how the data arrays can be read:

  fid = fopen('Iowa_AMSR_E_L3_DailyLand_X1_20020601.bin','r','ieee-be');
  TB06vr1a = fread(fid,[24 35],'integer*2') * 0.1;
  TB06hr1a = fread(fid,[24 35],'integer*2') * 0.1;
  TB10vr1a = fread(fid,[24 35],'integer*2') * 0.1;
  TB10hr1a = fread(fid,[24 35],'integer*2') * 0.1;
  TB18vr1a = fread(fid,[24 35],'integer*2') * 0.1;
  TB18hr1a = fread(fid,[24 35],'integer*2') * 0.1;
  TB36vr1a = fread(fid,[24 35],'integer*2') * 0.1;
  TB36hr1a = fread(fid,[24 35],'integer*2') * 0.1;
  TB36vr4a = fread(fid,[24 35],'integer*2') * 0.1;
  TB36hr4a = fread(fid,[24 35],'integer*2') * 0.1;
  TB89vr4a = fread(fid,[24 35],'integer*2') * 0.1;
  TB89hr4a = fread(fid,[24 35],'integer*2') * 0.1;
  TB06vr1d = fread(fid,[24 35],'integer*2') * 0.1;
  TB06hr1d = fread(fid,[24 35],'integer*2') * 0.1;
  TB10vr1d = fread(fid,[24 35],'integer*2') * 0.1;
  TB10hr1d = fread(fid,[24 35],'integer*2') * 0.1;
  TB18vr1d = fread(fid,[24 35],'integer*2') * 0.1;
  TB18hr1d = fread(fid,[24 35],'integer*2') * 0.1;
  TB36vr1d = fread(fid,[24 35],'integer*2') * 0.1;
  TB36hr1d = fread(fid,[24 35],'integer*2') * 0.1;
  TB36vr4d = fread(fid,[24 35],'integer*2') * 0.1;
  TB36hr4d = fread(fid,[24 35],'integer*2') * 0.1;
  TB89vr4d = fread(fid,[24 35],'integer*2') * 0.1;
  TB89hr4d = fread(fid,[24 35],'integer*2') * 0.1;
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Data Acquisition and Processing

Derivation Techniques and Algorithms

Processing Steps

The level 3 data are derived from level 2A source data. (See the AMSR-E/Aqua L2A Global Swath Spatially-Resampled Brightness Temperatures (Tb) documentation.) Level 3 gridded data were derived by resampling the level 2A swath data to the 25 km cylindrical EASE-Grid projection, using bin-averaging, and then compositing the daily swaths into separate ascending and descending grids. To associate a given array value with its location, refer to the latitude file "Iowa_lat.txt" and the longitude file "Iowa_lon.txt." For details regarding the EASE-Grid projection, please see All About EASE-Grid.

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Contacts and Acknowledgments

Eni G. Njoku
Steven Chan

Jet Propulsion Laboratory
Pasadena, California

Document Information


March 2004

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