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.
RESTRICTED only accessable in CEN/MPI network or via CliSAP login What does that mean?
Data access via file system: /data/icdc/ice_and_snow/smos_tb
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.
|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%|
Period and temporal resolution:
- 01/01/2010 - today
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
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.
email: xiangshan.tiankunze (at) awi.de
Alfred Wegener Institute for Polar and Marine Research / Bremerhaven
email: lars.kaleschke (at) awi.de
ICDC / CEN / University of Hamburg
email: stefan.kern (at) uni-hamburg.de
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, icdc.cen.uni-hamburg.de, University of Hamburg, Germany, Digital media.