QuikSCAT/SeaWinds Ultra High Resolution Ocean Sigma-0
and Ultra High Resolution Winds
Resolution enhancement algorithms such as those used for making
enhanced resolution sigma-0 images over land, can also be applied
to QuikSCAT and SeaWinds data due the high sampling density. Further,
enhanced resolution backscatter images can be generated from single
pass, single azimuth look measurements, enabling wind retrieval
at the pixel resolution of the imagery. Experimental products for
ultra high resolution ocean sigma-0 images and ultra high resolution
wind retrieval have been developed at BYU and are currently being
distributed. Some sample visualizations of hurricanes are presented
here. (Not every pass is shown.) These are browse *.gif images.
Example binary files can be obtained from David Long at the Scatterometer
Climate Record Pathdinfer (SCP) project. Real-time ultra high resolution
wind and related products based on our algorithms are available from
NOAA courtesy of Paul Chang.
Please note that ultra high resolution winds are an experimental product produced from NRT data and have significant limitations, particularly near coasts. Performance varies across the swath. Ambiguity removal performance is somewhat worse than conventional 25 km winds. Product validation continues and is encouraging but does point to the fact that the high resolution estimates are noisy and can be biased, particularly at low wind speeds. Note that ultra high resolution winds currently have no rain flag, but show clear evidence of rain contamination (e.g. individual convective systems can be distinguished in many places.).
Hurricane Isabel Landfall (18 Sept. 2003, 16:01)
+ Single pass ocean backscatter images have 2.5 km/pixel image resolution
and are shown in a cross-track/along-track grid. Along-track is to the right,
cross-track is up. Upper left panel is forward looking, Vpol.
Upper right panel is after looking, Vpol.
Lower left panel is forward looking, Hpol.
Lower right panel is aft looking Hpol.
* note: To represent 2.5 km winds, these *.gif images are
huge (like 4k x 4k pixels). Some browsers can not handle the image sizes
and zooming is required to see details. The browse images are reduced
resolution versions of these images, while the storm center images are
full resolution but are reduced in size, showing only a zoomed in view
of the storm center (and still quite large gif images).
In the ultra high resolution imagery land is shown in grey
while the background field is the high resolution (2.5 km/pixel)
SeaWinds/QuikSCAT wind speed estimates derived from the ultra high
resolution ocean sigma-0 field. The black arrows show the conventional
25 km MGDR wind directions. The smaller blue arrows (only seen when image
is zoomed in) are the average ultra high resolution direction computed
within an 8 x 8 (12km X 12km) box centered on the plotted arrow's tail.
Blue arrows are spaced 5 km apart.
Since radar backscatter is related to wind speed and
due to the reduced wind speed in the hurricane eye, the eye tends to be very visible
in high resolution sigma-0 images as a low-valued area in the midst of a high
backscatter region. Since the radar signal also scatters from rain, which
is not symmetric about the eye the apparent location of the eye can be
shifted somewhat in the backscatter images. Rain and wind bands can often be resolved in the backscatter and wind imagery.
Hurricane Fabian Timeseries (Sept. 2003)
Labeled time within approximately a minute or so of the actual pass time
over storm center. This data is selected from Near-Real-Time (NRT) processsing. A
more complete dataset, which includes both QuikSCAT and SeaWinds, is available
via the anonymous file
Site in the outgoing/data/mb/HiRes
subdirectory.
Pass time, day (2003) |
Conventional
25 km MGDR winds
|
Enhanced resolution
ocean backscatter+
|
Full-size ultra high res winds* |
Browse ultra
high res winds
|
Storm center
ultra high res winds
|
20:36,240 |
gif |
gif |
gif |
gif |
gif |
08:56,242 |
gif |
gif |
gif |
gif |
gif |
21:24,242 |
gif |
gif |
gif |
gif |
gif |
08:31,243 |
gif |
gif |
gif |
gif |
|
09:45,244 |
gif |
gif |
gif |
gif |
gif |
21:12,244 |
gif |
gif |
gif |
gif |
gif |
09:20,245 |
gif |
gif |
gif |
gif |
gif |
21:46,245 |
gif |
gif |
gif |
gif |
gif |
10:10,247 |
gif |
gif |
gif |
gif |
gif |
22:33,247 |
gif |
gif |
gif |
gif |
gif |
09:45,248 |
gif |
gif |
gif |
gif |
gif |
22:06,248++ |
gif |
gif |
gif |
gif |
gif |
09:22,249 |
gif |
gif |
gif |
gif |
gif |
08:57,250 |
gif |
gif |
gif |
gif |
gif |
21:11,250 |
gif |
gif |
gif |
gif |
gif |
++ Bermuda "hit".
Software for reading BINARY high resolution ocean sigma-0 (*.avewr)
files and BINARY high resolution wind files (*.WRave3) files are
available from the Scatterometer Climate Record Pathfinder (SCP)
anonymous file
Site in the software/HRsoftware
subdirectory. Contact David Long for additional high resolution wind files.
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