Integrated Climate Data Center

L3B SMOS Brightness Temperature

CliSAP/KlimaCampus Product

 

Left: Mean daily brightness temperature (TB) -intensity in the Northern hemisphere over open water, sea ice, and some of the adjacent land masses for December 1, 2012. Right: Corresponding standard deviation calculated as the variation of TB data pairs of the respective grid cell.

 

Access

RESTRICTED only accessable in ZMAW network or via CliSAP login What does that mean?

Data access via file system: /data/icdc/ice_and_snow/smos_tb

 

Description

The Microwave Imagine Radiometer with Aperture Synthesis (MIRAS) aboard the SMOS satellite measures the Earth's surface brightness temperature at L-Band at a frequency of 1.4 GHz. These measurements are full polarimetric and are carried out at nadir incidence angles of between 0 and 65°. Both polar hemispheres are covered completely every day.

Here we offer mean daily brightness temperature intensities gridded onto a polar-stereographic grid with 12.5 km grid resolution. In order to do so, first all brightness temperature (TB) measurements carried out during one day at both polarizations (horizontal and vertical, h and v) and nadir incidence angles of between 0 and 40° are collected on the special SMOS ISEA grid (The special viewing geometry of SMOS required a special native grid.). TBh and TBv have to acquired within 2.5 s to form a data pair to be used. For each SMOS ISEA grid cell all TB values are averaged over the given incidence angle range to compute the brightness temperature intensity (TBh + TBv)/2. Subsequently, the data are interpolated onto the mentioned polar-stereographic grid.

The documentation reveals more details of the processing.

 

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Parameters

Name Unit
Brightness Temperature Intensity K
Brightness Temperature Intensity standard deviation K
Number of TB data pairs per grid cell  
Relative fraction of RFI contaminated grid cells 0-100%

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Coverage, spatial and temporal resolution

Period and temporal resolution: 

  • 01/01/2010 - today
  • Daily

Data gaps exist during the Commissioning Phase (Jan.-May 2010) and from Dec. 27-31, 2010, due to problems with the antenna.

Coverage and spatial resolution:

  • Northern & Southern hemisphere poleward of 50°N & 50°S, respectively
  • Spatial resolution: 12.5 km x 12.5 km, polar-stereographic grid of the NSIDC, centered at 70°N and 70°S, respectively
  • Geographic longitude: 0°E to 360°E
  • Geographic latitude: 50°N and 50°S to 90°N and 90°S, respectively
  • Dimensions: 608 columns x 896 rows (Northern hemisphere), 632 columns x 664 rows (Southern hemisphere)
  • Altitude: 0.0m

Format:

  • NetCDF

Data quality

This data set contains the standard deviation of the TB intensity. For this all TBh / TBv pairs that are used to compute the daily average TB intensity for the respective ISEA grid cell are considered. The resulting standard deviation values are interpolated into the 12.5 km grid and are a measure for the variation of TB Intensity for the respective day and incidence angle range of 0-40°. An estimation of the representativity of these standard deviations is possible with the number of TBh - TBv data pairs given in the data set as well, also interpolated into the 12.5 km grid.

Radio Frequency Interference (RFI) is one of the major problems in SMOS data processing. Although RFI sources are known and a lot has been done in the past to mitigate RFI influence on SMOS data by deleting RFI sources still RFI cannot be excluded. Therefore the data set contains in addition for each grid cell the relative fraction of TB data pairs that have been discarded from the computation of the TB intensity because of RFI.

More details can be found in the documentation.

 

Contact

SMOSIce Project Scientist
Xiangshan Tian-Kunze
CliSAP / KlimaCampus / Institute of Oceanography
email: xiangshan.tian-kunze@we dont want spamzmaw.de

SMOSIce Project Principal Investigator
Lars Kaleschke
CliSAP / KlimaCampus / Institute of Oceanography
email: lars.kaleschke@we dont want spamzmaw.de

Stefan Kern
CliSAP / KlimaCampus / ICDC
email: stefan.kern@we dont want spamzmaw.de

 

Data citation

Please refer to 

X. Tian-Kunze, L. Kaleschke, and N. Maass (2012), updated current
year. SMOS Daily Polar Gridded Brightness Temperatures, [list
dates of temporal coverage used]. ICDC, http://icdc.zmaw.de, University of Hamburg, Germany, Digital media.

 

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