Technology Innovation - Cross-beam Wind Estimation Using Spaced Antenna Method
A Doppler radar measures only the radial component of the 3D wind field. However, all the wind
components are needed to characterize the state of the atmosphere, which is particularly important
for jet launch/recoverycycles on a carrier. Although a wind vector can be derived using dual
Doppler analysis (e.g.,
Doviak and Zrnic, 1993) or a bistatic radar network
(Wurman et al., 1993),
many efforts have been made to obtain a wind vector or transverse component using single-Doppler
velocity retrieval (SDVR).
For example, the storm motion can be determined by tracking the feature
in the reflectivity field using Tracking Reflectivity Echoes by Correlation (TREC)
(Rinehart and Garvey, 1978;
Tuttle and Foote, 1990).
However, the storm motion is not necessarily the same as
wind velocity and TREC is limited when the reflectivity is homogeneous. Other SDVRs
(Qiu and Xu, 1992;
Gao et al., 2001),
while more advanced, still rely on certain conservation assumption and
require multiple time levels of data to achieve a reasonable accuracy of the retrieved parameters.
The SA method was developed in the early ionospheric measurements of velocity using spatially
separated receivers
(Briggs et al., 1950). The idea is that the time-displacement measured between
the amplitude of signals from a pair of spatially separated receivers is related to the motion of
scatterers in the direction along the two receivers (cross-beam direction).
A mobile X-band SA system was recently developed to measure the wind vector field in convective
storm environments
(Pazmany et al., 2004;
Hardwich et al., 2005).
In addition, the Multiple Antenna Profiler Radar (MAPR) at NCAR was modified to be temporarily mounted on a pedestal
to horizontally scan through storms to obtain the cross-beam wind measurements
(Brown et al., 2005).
The application of the SA method on weather radar will be tested and verified using the PAR
emulator. The impact of additional cross-beam wind measurement on numerical prediction will
be evaluated and quantified using the OSSE. Although the current PAR
at NWRT uses one receiver, it is possible to access signals from left and right halves of SPY-1
antenna through some modifications. As a result, the wind component in the direction parallel to
the baseline of the two receivers can be obtained.