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Description

This dataset contains the latest reprocessed version 4.1 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 4.1 processing begins with the same L1B (time-ordered backscatter) data as used in the previous Version 4.0 processing. This new version has a number of key improvements and changes over the previous version 4.0, including: 1) winds are now retrieved 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.

Product Summary

Platforms
QUIKSCAT
Instruments
SEAWINDS
Spatial Extent

N: 90 S: -90 E: 180 W: -180

Spatial Resolution
12500 Meters x 12500 Meters
Geographic Region
GLOBAL OCEAN
Coordinate System
CARTESIAN
Granule Spatial Representation
CARTESIAN
Temporal Extent
1999-10-27 to 2009-11-22
Data Partner
Physical Oceanography Distributed Active Archive Center, Jet Propulsion Laboratory, NASA (NASA/JPL/PODAAC) ,
SeaWinds Processing and Analysis Center, Jet Propulsion Laboratory, NASA (NASA/JPL/SeaPAC)
Concept ID
C2036882397-POCLOUD
Data State
COMPLETE
Number of Files/Granules
51974
Processing Level
2
Published
Updated
Science Keywords
Surface Winds ,
Surface Winds

Citation

Citation is critically important for dataset documentation and discovery. This dataset is openly shared, without restriction, in accordance with the EOSDIS Data Use and Citation Guidance.

Copy Citation

SeaPAC. (2020). QuikSCAT Level 2B Ocean Wind Vectors in 12.5km Slice Composites Version 4.1 [Data set]. NASA Physical Oceanography Distributed Active Archive Center. https://doi.org/10.5067/QSX12-L2B41 Date Accessed: 2025-12-14

Documents

Variables

Variables are a set of physical properties whose values determine the characteristics or behavior of something. For example, temperature and pressure are variables of the atmosphere. Parameters and variables can be used interchangeably. Variable level attributes provide individual information for each variable.

The Name in this table is the variable name. Fill value indicates missing or undefined data points in a variable. Valid range is the range of values the variable can store. Scale factor is used to increase or decrease the size of an object and can be used to correct for distortion. For questions on a specific variable, please use the Earthdata Forum.

Name Description Units Data Type Fill Value Valid Range Scale Factor
ambiguity_direction wind direction ambiguity degrees float -9999 0 to 360 1
ambiguity_obj wind objective function values 1 float -9999 -199 0 1
ambiguity_speed wind speed ambiguity m s-1 float -9999 0 to 100 1
atmospheric_speed_bias atmospheric speed bias m s-1 float -9999 -100 to 100 1
cross_track_wind_speed_bias relative wind speed bias with respect to sweet spot m s-1 float -9999 -100 to 100 1
distance_from_coast Distance from nearest coastline km float N/A -25000 to 25000 1
eflags extended wind vector cell quality flags bit short 32767 0 to 7967 1
exp_bias_wrt_oceanward_neighbors Expected bias between the current cell and geographically oceanward neighboring cells. m s-1 float N/A -1000 to 1000 1
flags wind vector cell quality flags bit short 32767 0 to 32739 1
gmf_sst Sea Surface Temperature from NCAR Optimum Interpolation V2 product used during wind retrieval. Degrees Celsius float N/A -1000 to 1000 1
lat latitude degrees_north float N/A -90 to 90 1
lon longitude degrees_east float N/A 0 to 360 1
nudge_wind_direction model wind direction degrees float -9999 0 to 360 1
nudge_wind_speed model wind speed m s-1 float -9999 0 to 100 1
number_in_aft number of inner aft looks in wind vector cell 1 byte 0 1 to 127 1
number_in_fore number of inner forward looks in wind vector cell 1 byte 0 1 to 127 1
number_out_aft number of outer aft looks in wind vector cell 1 byte 0 1 to 127 1
number_out_fore number of outer forward looks in wind vector cell 1 byte 0 1 to 127 1
num_ambiguities number of ambiguous wind directions found in point-wise wind retrieval prior to spatial filtering 1 byte 0 1 to 4 1
rain_impact impact of rain upon wind vector retrieval 1 float -9999 0 to 100 1
retrieved_wind_direction equivalent neutral wind direction at 10 m degrees float -9999 0 to 360 1
retrieved_wind_speed equivalent neutral wind speed at 10 m m s-1 float -9999 0 to 100 1
retrieved_wind_speed_uncorrected wind speed without rain correction m s-1 float -9999 0 to 100 1
time date and time seconds since 1999-1-1 0:0:0 double N/A N/A 1
wind_obj retrieved wind objective function value 1 float -9999 -199 0 1
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