NSCAT Level 2 Ocean Wind Vector Ambiguity Removal Overlay (Hoffman, AER)
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DescriptionThis dataset contains the NASA Scatterometer (NSCAT) Level 2 ocean wind vector ambiguity overlay files for the NSCAT MGDR version 2 dataset, referenced for 25 km wind vector cells (WVC). The dataset is derived from the results of a study which used a 2-D variational analysis method (VAM) to select a wind solution from the NSCAT ambiguous winds (Hoffman et al. 2003). Hoffman et al. chose the ambiguity closest in direction to the VAM surface wind analysis. No ambiguity was chosen for poor quality wind vector cells (WVCs). ECMWF analyses were used as the background field for the VAM. Their choice of ambiguity selection is compared with that of JPL, which used a median filter initialized with NCEP analysis fields. Ambiguity selection is changed in ~5% of the dataset, often improving the depiction of meteorological features where the surface wind is strongly curved or sheared. See Hoffman et al. (2003) for more on the method and results. Additional work by Henderson et al. (2003) compares the results of median filtering (JPL) vs. the 2d-VAR method (Hoffman et al., 2003) using 51 days of NSCAT data, supplemented by the NCEP 1000 hPa wind analyses as background fields.
Dataset TypePREVIEW
MeasurementOCEANS > OCEAN WINDS > SURFACE WINDS > Wind Vector Cell Ambiguity Removal
Processing Level2
CoverageRegion: Global
Northernmost Latitude: 90 degrees
Southernmost Latitude: -90 degrees
Westernmost Longitude: 0 degrees
Easternmost Longitude: 360 degrees
Time Span: 1996-Sep-15 to 1997-Jun-29
ResolutionSpatial Resolution: 25 km (Along) x 25 km (Across)
ProjectionType: Swath
Detail: Along-track Grid
Ellipsoid: WGS 84
Latency hours
Swath Width1600000 m
Sample Frequency-
Temporal Repeat (Nominal)12 Hour
Temporal Repeat (Min)1.7 Hour
Temporal Repeat (Max)41 Day
Name: Advanced Earth Observing Satellite-I (ADEOS-I)
Orbit Period: 100.92 minutes
Inclination Angle: 98.59 degrees
Ascending Node: 1996-Sep-14 22:20:33
Name: NASA Scatterometer (NSCAT)
Swath Width: 1600 km
Description: Every two days, under all weather and cloud conditions, NSCAT measured wind speeds and directions over at least 90% of the Earth's ice-free oceans. NSCAT used six antenna beams to scan two wide bands of ocean, one on each side of the instrument's orbital path. NSCAT transmited short pulses of microwave energy to probe ocean surfaces and then measured the reflected or backscattered power. Variations in the magnitude of this backscattered power are caused by changes in small (centimeter-sized), wind-driven waves. Using a method called Doppler processing, the measured backscattered power was separated into cells at specific locations on Earth's surface.

ProjectNASA Scatterometer (NSCAT)
Data ProviderCreator: NASA/JPL/PO.DAAC
Release Place: PO.DAAC
Release Date: 1998-Jul-25
Resource: -
Keyword(s)ambiguity removal, nscat, adeos, scatterometer, hoffman, aer
Questions related to this dataset? Contact podaac@podaac.jpl.nasa.gov
Citation NASA/JPL/PO.DAAC. 1998. NSCAT Level 2 Ocean Wind Vector Ambiguity Removal Overlay (Hoffman, AER). Ver. 2. PO.DAAC, CA, USA. Dataset accessed [YYYY-MM-DD] at https://doi.org/10.5067/NSAER-L2AR0.

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For more information see Data Citations and Acknowledgments.

Journal Reference Hoffman, R. N., S. M. Leidner, J. M. Henderson, R. Atlas, J. V. Ardizzone, and S. C. Bloom, 2003: A two-dimensional variational analysis method for NSCAT ambiguity removal: methodology, sensitivity, and tuning. J. Atmos. Oceanic Technol., 20, 585-605.