Brightness Temperatures from L3B SMOS

Arctic Brightness Temperature Intensity December 2012 — Mean daily brightness temperature intensity (TB) in the Northern hemisphere over open water, sea ice, and some of the adjacent land masses for December 1, 2012 (top) and corresponding uncertainty (bottom). Copyright: UHH/CEN/AJB.

Arctic Brightness Temperature Uncertainty December 2012 — Mean daily brightness temperature intensity (TB) in the Northern hemisphere over open water, sea ice, and some of the adjacent land masses for December 1, 2012 (top) and corresponding uncertainty (bottom). Copyright: UHH/CEN/AJB.

Topics

Access

UNRESTRICTED:

View TB data at LAS
Get TB data via HTTP (wget shell script to get all data)
Access TB data via OPeNDAP

RESTRICTED:This link to the data set is only available for a restricted user group. The data set is only accessible in CEN/MPI net or accessible from external nets with a customer account. Please contact ICDC if you would like to access this data from outside the network.

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

to top

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.

Attention! Since Dec 2, 2016 version 3 is available. The data are reprocessed consistently using v620 L1C data. An improved data filtering method regarding to RFI and geophysical noises is applied in the processing chain from L1C to L3B, which improved the L3B data quality and availability.

The documentation reveals more details of the processing (see references).

This data set is a CliSAP/KlimaCampus product.

Last update of data set at ICDC:

to top

Parameters

Parameters of the brightness temperature data set
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	%

to top

Coverage, spatial and temporal resolution

Period and temporal resolution:

01/01/2010 - 30/09/2019
Daily

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 (see references), 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

to top

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 mentioned in the references.

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

to top

Contact

Project Scientist
Xiangshan Tian-Kunze
email: xiangshan.tiankunze (at) awi.de

Principal Investigator
Lars Kaleschke
Alfred Wegener Institute for Polar and Marine Research / Bremerhaven
email: lars.kaleschke (at) awi.de

Stefan Kern
ICDC / CEN / University of Hamburg
E-Mail: stefan.kern"AT"uni-hamburg.de

to top

References

Literature:

Documentation SMOS Daily Polar Gridded Brightness Temperatures (L3B), Tian-Kunze et al., 2016 (pdf, not barrier-free)
Kaleschke et al., Sea ice thickness retrieval from SMOS brightness temperatures during the Arctic freeze-up period, GEOPHYSICAL RESEARCH LETTERS, VOL. 39, L05501, doi:10.1029/2012GL050916, 2012, (pdf, not barrier-free)

Websites:

NSIDC Geocoordinate and Pixel-Area Tools, https://nsidc.org/data/polar-stereo/tools_geo_pixel.html

to top

Data citation

Please cite the data as follows:

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, CEN, University of Hamburg, Germany, Digital media.

and with the following acknowledgments:

Thanks to ICDC, CEN, University of Hamburg for data support.

to top