High resolution 3D wind profiling using an S-band polarimetric FM-CW radar: dealiasing techniques

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

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)

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

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

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

International Research Centre for Telecommunications and Radar

Main beam: polarimetric dealiasing technique

International Research Centre for Telecommunications and Radar

Main beam: polarimetric dealiasing technique

International Research Centre for Telecommunications and Radar

Profiles of mean Doppler velocities for the 3 beams

Classical dealiasing Polarimetric dealiasing

International Research Centre for Telecommunications and Radar

Resulting horizontal wind retrievals

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.

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

International Research Centre for Telecommunications and Radar

Offset beam: classical dealiasing technique

Precipitation event

slant profile

Aliased Doppler spectra

Doppler velocity [m/s]

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