Wind Field Observations with a Monostatic and Bistatic C ... - WakeNet

Wind Field Observations with 

a Monostatic and Bistatic 

C-band Doppler Radar Network 

Institut für Physik der Atmosphäre 

Martin Hagen 

Institut für Physik der Atmosphäre, DLR Oberpfaffenhofen

Wind field and Doppler radar 

Doppler radar (and lidar) can only measure one component 

(the radial one) of the 3-dimensional wind vector 

v r 

w 

v 

u 

-16 0 m/s 16 


Martin Hagen, Wakenet-3 Wind Workshop, Palaiseau, 29 - 30 March 2010 

2

Wind field and Doppler radar 

Estimation of the 3-dimensional 

single Doppler wind field techniques (VAD, VVP, UWT, ...) 

make assumptions about the 

wind field (linear, homogeneous, 

constant) within a region 

(dimension of several kilometres) 

requires more than one radar 

(or lidar) 

vertical air motion can not be 

retrieved, it will be estimated by 

vertical integration of convergences 

of the horizontal wind field (3d-var, 4d-var techniques) 



3

Monostatic and Bistatic Doppler Radar Network 

Monostatic radar network: 

same antenna for 

transmit and receive 

Bistatic radar network: 

different antennas for 


Bistatic 

Receiver 



4

Monostatic Doppler Radar Network 

Monostatic radar network: 

same antenna for 


minimum 2, better more radars (or lidars) are required 

synchronized scanning 

short distance (20 – 40 km) between radars to 

cover low-level wind field features close to the 

airport (operational networks: distance 100 - 200 km) 



5

Monostatic Doppler radar network 

Estimation of horizontal wind vector 

with measurements from two 

Doppler radars 

Highest accuracy if intersection 

angle γ = 90° 

Sufficient accuracy for 30° < γ < 150° 

St. dev. hor. wind (m/s) 

10 

8 

6 

4 

2 

0 

0 30 60 90 120 150 180 

Intersection angle (°) 

assumed st. dev. of Doppler velocity 1 m/s 

Radar 2 

90° 

Basislinie 

120° 

Radar 1 

60° 



6

Monostatic and Bistatic Doppler Radar Network 

Bistatic radar network: 

different antennas for 



Receiver 

Bistatic radar network uses one active (transmit and receive) radar 

and several passive receivers 

measurements are synchronized in time and space 

bistatic receivers are cheap (0.1 vs. 1.5 M€) 

distance between receivers – radar: 20 – 40 km 



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Bistatic Doppler radar network 

Horizontal wind composed from 

radial Doppler velocity measured by radar (v r ), 

(elliptical) Doppler velocity measured by bistatic receiver (v e ). 

accuracy is reduced since 

intersection angle between 

v e and v r = ½ scattering angle γ 

St. dev. hor. wind (m/s) 

10 

8 

6 

4 

2 

0 

bistatic 

monostatic 

assumed st. dev. of Doppler velocity 1 m/s 

0 30 60 90 120 150 180 

scattering angle (°) 

r t 

v e 

v r 

scattering 

angle γ 

Transmitter 

+ Receiver 

r b 

Receiver 



8

Monostatic versus bistatic Doppler radar network 

Reduced accuracy and areal coverage can easily be compensated 

by a larger number of receivers 

monostatic 2 radars bistatic 1 radar 1 receiver bistatic 1 radar 3 receivers 



9

Bistatic Doppler radar network 

first trials 1993: NCAR / Univ. of Oklahoma 

challenge: synchronization of oscillator at radar and remote site 

for accurate phase estimation 

available systems for research: 

McGill University Montreal (1996 – 2002 ?) 

first permanent installation, klystron transmitter 

NCAR S-Pol radar field campaigns 

e.g. IMPROVE I at Pacific coast (2001) 

NICT Japan, Okinawa (2003 ?) 

C-band, klystron transmitter, GPM ground validation site 

DLR Oberpfaffenhofen (1998 – 2005; 2010 - ) 

first C-band system with magnetron transmitter 



10

Overview of DLR 

bistatic radar net 

Radar POLDIRAD 

Bistatic receiver 

at radar 

Remote bistatic 

receiver 

Hub: 

central processor 

and 

communication 

POLDIRAD 

System 

antenna 

angles, 

trigger 

GPS 

antenna 

Phasedetection 

synchronized 

with GPS signal 

local display 

phase 

of tx 

pulse 

Radar 

data 

unit 

Radarcontrol 

Magnetron 

Dopplervelocity 


Reflectivity 

Receiver at the radar 

Doppler 

R 

velocities 


B1 reflectivities 

from both 

receivers 

Realtime 

wind 

vectors 

Central bistatic vector processor 


I, Q 

Veloc. Refl. 

Radar 

antenna 

TCP/IP 

network 

with ISDN 

routers 



antenna 

Azim., Elev., 

time, phase 

Dopplervelocity 


Veloc. Refl. Reflectivity 

Phasemeasurement 

synchronized 

with GPS signal 

local display 

Remote receiver 

GPS 

antenna 

11

Bistatic Doppler radar network at DLR Oberpfaffenhofen 

Lagerlechfeld 

Ri ed 

MÜNCHEN 

Dual-Doppler 

Triple-Doppler 

4-Doppler 

Oberpfaffenhofen 

10 km 

20 km 

11,7 km 

Licht enau 

30 km 

40 km 

50 km 

Antenna aperture Horizontal Vertical 

Lichtenau 60° 8°, 22° 

Lagerlechfeld 60° 8°, 22° 

Ried 60° 8° 



12

Bistatic Doppler radar network at DLR Oberpfaffenhofen 

Lagerlechfeld Lechfeld 



13

DLR bistatic Doppler radar network wind synthesis 

Doppler velocity radar receiver Lechfeld receiver Ried 

receiver Lichtenau 



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Observation of thunderstorm outflow 

9 July 2002 

1557 UTC 

Elevation 5.4° 



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Observations in clear-air echoes 

Clear-air echoes give 

good radar coverage 

at short distances 

(~50 km) during 

summer (insects) 

Minimum detectable 

signal of bistatic 

receivers is less than 

for monostatic radars 

due to reduced 

antenna gain 

~10 vs. 45 dB 



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Evaluation of bistatic Doppler wind field 

Independent Doppler measurements at Hohenpeißenberg 

Vh 

BINET 

Vr 

HP from BINET 

Difference 

Vr 

HP meas. 

Friedrich & Hagen, 2004 

JTECH, 21, 1840-1854 



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Conclusion Bistatic Doppler radar network 

Advantages: 

Low costs for a multiple Doppler radar system 

high resolution (pulse volume) wind field estimates 

temporal synchronized measurements 

Disadvantages: 

reduced sensitivity (clear-air observations unlikely) 

contamination by 

side-lobes of radar 

Production and support 

of systems stopped 

Friedrich, 2002, PhD thesis 



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Wind Field Observations with a Monostatic and Bistatic C ... - WakeNet

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