SeaWinds on QuikScat
|
Northern and Southern Polar Hemisphere Views from
the SeaWinds Scatterometer on QuikScat
|
SeaWinds on ADEOSII
(To be launched Nov. 2001)
|
The MERS research group has been actively involved in polar research
in the northern and southern hemisphere. As part of these studies
the Seawinds scatterometer on QuikScat (QSCAT) data has been processed
with the Scatterometer Image Reconstruction (SIR) algorithm. This
algorithm was developed by the MERS lab to generate enhanced resolution
scatterometer imagery.
SIR generates 'A' images. The resolution of the resulting
images is as fine as ~4-5 km for QSCAT. Previous techniques
were limited to the intrinsic resolution (typically 25 km) of the
scatterometer.
Antarctic Images And Movies
All movies are made using QSCAT images unless otherwise
specified.
These images have been down sampled from original sizes.
These movies are available in mov, avi, Animated gif formats.
(Movie Notation: h,v=horizontally or vertically
polarized; ave, sir =ave or sir images; 99 or 00= year; JD296=Julian
Day)
QSCAT Antarctic Images And Movies
While satellite microwave radar scatterometers were originally
designed to measure winds over the ocean from space, they can also
be useful in polar ice studies. Using the Scatterometer Image Reconstruction
with Filtering (SIRF) resolution enhancement algorithm we have generated
a time series of radar images of the Antarctic region. New methods
for mapping the spatial extent and ice type have been developed
for use with QSCAT data. The results enable study of the dynamics
of the sea-ice sheet and permit multidecadal studies of change by
comparison with previous scatterometers. The broad coverage, dual-pol
measurements, and high resolution of QSCAT yield very high quality
images.
Microwave radar mitigates the need for optimal meteorological conditions
and solar illumination which can hamper optical sensors. The radar
scattering signal provides insight into characteristics of the ice
which can not be inferred from optical images. In particular, the
microwave images depend on both surface roughness and the electrical
properties, which vary for different ice types, enabling the retrieval
of ice characteristics from the radar data. Knowledge of the ice
characteristics is of crucial import in modeling the interaction
of the ocean and atmosphere in the polar regions and in evaluating
the Earth's heat balance. Sea-ice cover also influences the production
of Antarctic Bottom Water, a crucial factor in global ocean circulation.
QSCAT makes measurements at both vertical and horizontal electrical
polarization. Sea-ice has a nearly isotropic response while the
ocean exhibits a very directional response which is ordinarily used
to determine the direction of the wind blowing over the surface.
While the sea-ice evolves on time scales of days to weeks, winds
over the ocean can change on hourly time scales. Using images of
the vertical and horizontal radar response and the temporal variation
in the radar response over a several day period, the spatial extent
of the sea-ice can be mapped. The resulting ice edge compares favorably
with passive microwave ice maps but has higher spatial resolution
and precision.
|