NSCAT VAM Ambiguity Removal Overlay (Hoffman et al. 2003)

Products / Announcements / Citations/Ref.

Product Description
The overlay files are the result of processing the entire 9 months of NSCAT 25 km MGDR (Merged Geophysical Data Product) data version 2.0. The files contain the results of a study to use a 2-D variational analysis method (VAM) to select a wind solution from the NSCAT ambiguous winds. They 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.

Synoptic View of Ocean Surface Winds Measured by NSCAT,
September 21, 1996

NSCAT VAM Ambiguity Removal Overlay (Hoffman et al. 2003)

PProducts

NNSCAT VAM Ambiguity Removal Overlay (Hoffman et al. 2003)	FTP	daily	25 km

Announcements
This product is currently in an experimental ‘preview’ stage and is being offered as-is, with no expressed provision of data-specific technical support to users by PO.DAAC staff. However, the PO.DAAC staff would like to know your opinions regarding this specific product, such as: how is it useful for your scientific needs, is it user friendly, does this product contain any bugs or errors, and what could be done to improve this product? Please direct your comments and concerns to: podaac@podaac.jpl.nasa.gov.

Citations/References
Henderson, J. M., R. N. Hoffman, S. M. Leidner, J. V. Ardizzone, R. Atlas, and E. Brin, 2003: A comparison of a two-dimensional variational analysis method and a median filter for NSCAT ambiguity removal. J. Geophys. Res., 108, doi:10.1029/2002JC001307.

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.