Collocated VOS observations (speed and direction) used in
the GEOS-1 analyses and NSCAT winds are quality controlled, and all
observations within the spatial and temporal collocation criteria and pass the quality control are averaged. Quality control
involves (1) gross comparison to GEOS DAS wind fields, (2) comparison to
variational analysis. Wind speeds are height adjusted to a ten meter reference
height.
Rather than converting the ship observations to equivalent neutral winds, they are height adjusted assuming a 19.5 m reference height, neutral atmospheric stratification, and a roughness length of 0.152 mm.
The ambiguity used in the comparison is the closest ambiguity rather than the selected ambiguity.
Buoys
Buoys used in the GEOS-1 analyses are processed in the same
manner as the VOS observations, except that the reference height is assumed to be 5 m.
SSM/I
25 km resolution SSM/I winds are bilinearly interpolated
to NSCAT observation locations.
NCEP
NCEP winds (2x2.5°) are bilineraly
interpolated to NSCAT observation locations.
GEOS
GEOS-1 winds are bilineraly interpolated, from a 2.0° latitude by 2.5° longitue grid, to NSCAT observation
locations.
ERS-2 Scatterometer
Winds
Collocated winds with the closest ambiguities (ERS-2 and
NSCAT) to the validation data set. A variational analysis method (VAM) was used to quality check the data as follows:
1) gross outliers eliminated using GEOS analysis.
2) variational analysis of data performed using GEOS analysis (as background) with weak constraints.
3) QC performed relative to the new analysis with tighter constraints.
Contacts
BobAtlas
atlas@hera.gsfc.nasa.gov
Steve Bloom sbloom@dao.gsfc.nasa.gov
Joe Terry jterry@dao.gsfc.nasa.gov
Joe Ardizzone jardizzone@dao.gsfc.nasa.gov
Reference
Atlas, R., S. C. Bloom, R. N. Hoffman, E. Brin, J. Ardizzone,
J. Terry, D. Bungato, and J. C. Jusem, 1998: Geophysical validation of
NSCAT winds using atmospheric data and analyses. J. Geophys. Res.,
NSCAT special issue.