Download - High resolution 3D wind profiling using an S-band polarimetric FM-CW radar: dealiasing techniques
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International Research Centre for Telecommunications and Radar
High resolution 3D wind profiling using an S-band polarimetric FM-CW radar: dealiasing techniques
Christine Unal, Herman RusschenbergDelft University of Technology, The Netherlands
Dmitri MoisseevColorado State University, Fort Collins, CO, USA
Type of measurement First main limitation: small Maximum Unambiguous Doppler velocityDealiasing techniques (polarimetric and classical)Example of Wind retrieval results
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International Research Centre for Telecommunications and Radar
Goal: Dynamics and Microphysics of Precipitation and Clouds Sensor: Doppler polarimetric radar TARA (S-band) High resolution in space (30-3 m) and time (1-10s) Location: Atmospheric profiling site Cabauw (synergy with other sensors)
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International Research Centre for Telecommunications and Radar
Measurement configuration
3 beams 3 mean Doppler velocities
horizontal wind + vertical wind
15o
OB1
Y
X
MBOB2
750
15o
elevation
vertical
MB
VV HV HH OB1 OB2
The max. unambiguous Doppler velocity is reduced by a factor 5
time
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International Research Centre for Telecommunications and Radar
Polarimetric de-aliasing
,max
4( ) 2D D Dl lv n V t
Expected differential phase ~ 0 at S-band
Measured differential phase:
Measured Doppler speed Maximum unambiguousDoppler speed
( ) 2 2cD D
s
t kl n n
nT n
Non simultaneity of VV and HH measurements
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International Research Centre for Telecommunications and Radar
Main beam: polarimetric dealiasing technique
,max ,max5 , 3D DV V
,max ,max3 ,D DV V
,max ,max,D DV V
,max ,max,3D DV V
,max ,max3 ,5D DV V
Expected differential phase ~ 0 at S-band
Measured differential phase shows different mean values in case of aliasing
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International Research Centre for Telecommunications and Radar
Main beam: polarimetric dealiasing technique
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International Research Centre for Telecommunications and Radar
Main beam: polarimetric dealiasing technique
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International Research Centre for Telecommunications and Radar
Profiles of mean Doppler velocities for the 3 beams
Classical dealiasing Polarimetric dealiasing
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International Research Centre for Telecommunications and Radar
Resulting horizontal wind retrievals
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International Research Centre for Telecommunications and Radar
Conclusions
High resolution profiling of horizontal wind in precipitation and clouds example with time resolution = 5 s and range resolution = 30 m
What has still to be doneImproved clutter suppression for non polarimetric beamsSeparation between fall velocities of hydrometeors and vertical windCorrection for effects of beam divergence (possible limitation for high altitudes clouds)
First ObjectivesDynamics of the boundary layer. Preparation for study of cloud-aerosol interaction.
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International Research Centre for Telecommunications and Radar
Main beam: polarimetric dealiasing technique
Applying the classification in 5 intervals, the Doppler spectra bins of targets with co smaller than 0.78 are placed in the wrong interval of Doppler velocities
Clutter and noise reduction
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International Research Centre for Telecommunications and Radar
Offset beam: classical dealiasing technique
Precipitation event
slant profile
Aliased Doppler spectra
Doppler velocity [m/s]
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International Research Centre for Telecommunications and Radar
Offset beam: classical dealiasing technique
Resulting spectrograph with dealiasing + noise reduction
,maxDVSearch for signal above noise level at
Unfolding (using max. spectral reflectivity)
Reference: Doppler spectrum of cloud
Range continuity check with a cross correlation function