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Data access via file system: /data/icdc/ice_and_snow/arctic_lead_fraction_cryosat2
Data obtained with the SIRAL instrument aboard the CryoSat-2 satellite are used to produce a data set of the percentage lead area fraction for winter months January, February, and March on the NSIDC polar-stereographic grid with 100 km grid resolution.
The first step is a supervised classification of different parameters derived from SIRAL measurements. The results of the classification are inter-compared with contemporary MODIS visible imagery with the goal to find the best parameter / parameter combination to identify leads in Arctic sea ice. The parameter with the best classification agreement to the MODIS imagery which - among the pulse peakiness - is the maximum power of the waveforms is used to derive the Arctic lead area fraction offered here.
For more details of the methodology and potential limitations we refer to the publications given in the references.
This data set has been published via ICDC on October 9 2015.
|Lead Area Fraction||0-100%|
|Number of data per month and grid cell||--|
|Sea ice mask||0,1|
Period and temporal resolution:
- Monthly, January to March (2015: February)
Coverage and spatial resolution:
- Northern hemisphere
- Spatial resolution: 100 km x 100 km, polar-stereographic grid from NSIDC, tangential plane at 70°N and 70°S, respectively
- Geographic longitude: -180°E to 180°E
- Geographic latitude: from about 41°N to 90°N, in the corners of the grid further equatorward
- Dimension: 76 columns x 112 rows
- Altitude: 0.0 m
The data set does not contain uncertainty estimates.
The validation of the lead detection mainly took place based on a comparisons between contemporary visual MODIS scenes and CS-2 tracks. The used classifier has been optimized by these scenes to minimize miss-classification of ice as leads and vice versa.
Independent validation by additional scenes confirms that nearly all leads wider than 250 m are detected. The detection behavior below this width cannot be quantified. Leads covered by newly formed thin ice are also detected but an upper boundary of ice thickness (or age) cannot also be estimated due to missing validation data.
The general lead distribution shows reasonable regional pattern and spatial transitions with slightly higher lead fractions than in previous estimates. This difference to those can be well explained by the ability to detect smaller leads compared, e.g., to the approach used to detect leads from AMSR-E data.
More details are found in the references.
Institute of Oceanography / CEN / University of Hamburg
email: andreas.wernecke (at) uni-hamburg.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