Friday, September 4, 2020

The PO.DAAC is pleased to announce the public release of the QuikSCAT Level 2B Ocean Wind Vectors in 12.5km Slice Composites version 4.1 dataset. More information regarding the QuikSCAT mission and instrumentation is available from PO.DAAC’s mission webpage.

This dataset provides the latest reprocessed version 4.1 of the Level 2B science-quality ocean surface wind vector retrievals from the QuikSCAT scatterometer in netCDF-4 format. The retrievals are provided on a non-uniform grid within the swath at 12.5 km pixel resolution. Version 4.1 processing begins with the same Level 1B (L1B) Sigma-0 (normalized radar cross-section) data as used in the previous Version 4.0 processing and continues the near coastal wind retrieval using the Land Contamination Ratio with Expected Sigma-0 (LCRES) technique. This new version has a number of key improvements and changes over the previous version 4.0, including: 1) winds are now retrieved using LCRES to within 5-km and 10-km of the coast within oceans/seas and lakes respectively; 2) coastal winds are now flagged as poor coastal quality and likely corrupted in orbits with estimated spacecraft pitch error greater than 0.04 degrees, which affects 150 orbits of data where coastal winds are severely contaminated by land due to poor attitude knowledge (note: attitude error tracking can identify pitch error but not yaw error, so when estimated pitch error is far from zero, it implies yaw error is large and uncorrected); 3) coastal winds are flagged based upon the long term mean wind speed and standard deviation of wind speed for each place on the ground; 4) four quantities, means and standard deviations computed with and without the land contamination correction algorithm applied (note: higher mean and smaller standard deviation are evidence of land contamination), are used to estimate the expected wind speed bias with respect to neighboring wind vector cells over open water; 5) wind vector cells with estimated speed bias greater than 0.4 m/s are flagged as poor coastal quality and likely corrupted; 6) winds within 5-km of the coast of an ocean/sea and 10-km of the coast of a lake are flagged as poor coastal quality and likely corrupted; the larger distance threshold for lakes is due to higher variability in lake water levels.

The QuikSCAT L2B version 4.1 dataset provides near-global, daily coverage from 1999-October-27 to 2009-November-22 and is described and discoverable via the PO.DAAC data portal.

Citation: SeaPAC. 2020. QuikSCAT Level 2B Ocean Wind Vectors in 12.5km Slice Composites Version 4.1. Ver. 4.1. PO.DAAC, CA, USA. Dataset accessed [YYYY-MM-DD] at

Comments/Questions? Please contact  or visit the PO.DAAC Ocean Wind Forum.