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QuikSCAT Level 2B Ocean Wind Vectors in 12.5km Slice Composites Version 4.0

This dataset contains the latest reprocessed version 4.0 of the Level 2B science-quality ocean surface wind vector retrievals from the QuikSCAT scatterometer. The retrievals are provided on a non-uniform grid within the swath at 12.5 km pixel resolution. Higher resolution is achieved through a slice composite technique in which high resolution slice measurements from L1B data are composited into a 12.5 km wind vector cell. Each L2B file corresponds to a specific orbital revolution (rev) number, which begins at the southernmost point of the ascending orbit. This is an official dataset produced by the NASA QuikSCAT Project through the SeaWinds Processing and Analysis Center (SeaPAC). Version 4.0 processing begins with the same L1B (time-ordered backscatter) data as used in the previous Version 3.1 processing. The new version has three important improvements over the previous version 3.1. First, a sea-surface temperature (SST) dependent geophysical model function (GMF) developed by Lucrezia Ricciardulli of Remote Sensing Systems is used in wind retrieval in order to fix persistent speed biases in Ku-band data over cold ocean. Second, near coastal winds are retrieved using the Land Contamination Ratio with Expected Sigma-0 (LCRES) technique which retrieves winds significantly closer to the coast than has been done before. Third, flagging is simplified and extra flags are provided. All of the legacy quality flags are preserved with the same meaning. A new single bit wind_retrieval_likely_corrupted_flag is established for conditions in which approximately 3% (or greater) of the data comprising a wind vector cell (WVC) exhibits suboptimal performance due to rain, ice, or a few other rare anomalous cases. Another bit wind_retrieval_possibly_corrupted_flag is established for conditions in which approximately 15% of the data comprising a WVC near rain, ice, or a coastal boundary is thought to be high quality but may not match up well with numerical wind models due to either remaining rain/ice/land contamination or variability in the winds near ice, rain, and coasts that are not reflected in the numerical weather prediction (NWP) matchups. In addition to these two new bits, copious quality information is provided in the flags and eflags variables to allow users to tailor flags to meet their own needs. New and legacy flag bits are described in more detail in the user guide.

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