Status of Dual-Doppler Wind Retrieval Project
Carpe Diem 6th Meeting
Helsinki
24 June 2004
by
Kheng
University of Essex
Recall in Dublin
● What we have done
– Shown visualisation examples produced by DARWIn
– Converted Polar data -> Cartesian
– Successfully constructed 3D wind fields
– Shown 2 case studies
Coordinates conversion II
Case I (17 Dec 2002) 1915hr : Dual-Doppler Wind Field
Case Studies
- Case I : (17 Dec 2002) 1915hr
- Case II : (15 Aug 2003) 1815 hr
Case I (17 Dec 2002) 1915hr : Gattatico Doppler Velocity
Case II (15 Aug 2003) 1815hr :Dual Doppler Wind Field
Remarks from Dublin meeting
● Problems & comments
– Limited data sets
– How to verify validity of the constructed 3D wind fields.
– Triple Doppler retrieval
– Comparison with NWP model
New data sets● 2003 July 13 – 14
– Bologna, Gattatico, scan time (00, 12, 15, 27, 30 ...)
● 2003 July 31
– Bologna, Gattatico, Teolo
● 2003 September 09
– Bologna, Gattatico
● 2003 November 11
– Bologna, Gattatico, Teolo
Case 1: (2003 Jul 13) 2330 hr 3.2o
PPI – Reflectivity
Gattatico Bologna
Case 1: (2003 Jul 13) 2330 hr 3.2o
PPI – Doppler Velocity
BolognaGattatico
Case 1: (2003 Jul 13) 2330 hr 3.2o
Wind Field
How do we know that the wind field is correct?
Numerical procedures● Iterative method:
– horizontal components
– vertical component
● Boundary conditions:
– zero velocity on ground
● Typical convergent factor
dzd
wzw
yv
xu
1
where0
030.0,,
)1(,,
)(
,,)(
,,)1(
max
kjin
kjin
kjin
kjin
ww
ww
11 , nnnn wDCvwBAu
Comparison of reconstructed radial velocity field and radar measurement
measurement
reconstruction
Gattatico Gattatico
Bologna Bologna
“along-track” components
r1
r2
r12
v . (r12 + r2 – r1) = 0
= v(cal).r12 + vr2 (obs) r2 – vr1 (obs) r1
Typical relative deviation, /(v .r12) < ±1%
v
Case 2: (2003 Jul 31) 1734 hr 3.1o
PPI – Gattatico
ZDRReflectivity
Case 2: (2003 Jul 31) 1734 hr 3.1o
PPI – Gattatico
ZDRReflectivity
Case 2: (2003 Jul 31) 1734 hr 3.1o
PPI – Bologna
ZDRReflectivity
Case 2: (2003 Jul 31) 1734 hr 3.1o
PPI – Bologna
ZDRReflectivity
Possibility of performing triple-Doppler analysis?
we are still trying because of ...
Case 2: (2003 Jul 31) 1730 hr 2.5o
PPI – Teolo
Doppler velocityReflectivity
Case 2: (2003 Jul 31) 1730 hrPPI – Doppler Velocity
Teolo 2.5oGattatico 3.1o
Case 2: (2003 Jul 31) 1730 hrPPI – Doppler Velocity
Teolo 2.5oGattatico 3.1o
Problems with Triple-Doppler
● Teolo – many rays are missing
● Teolo – Doppler radial velocity convention
● Teolo – 470 m asl, lowest elevation 0.9 deg
– Minimun height ~ 1400 m (centre)
● Gattatico & Bologna – ? m asl, lowest elevation 0.5 deg
– Minimun height ~ 600 m (centre)
– Next elevation ~ 1400 m (centre)
Case 3: (2003 Sep 09) 1315 hr 2.3o
PPI – Reflectivity
Gattatico Bologna
Case 3: (2003 Sep 09) 1315 hr 2.3o
PPI – Doppler Velocity
Gattatico Bologna
measurement
reconstruction
Case 3: (2003 Sep 09) 1315 hr 2.3o
PPI – Radial Velocity Comparison
Gattatico Gattatico
BolognaBologna
Case 3: (2003 Sep 09) 1315 hr3D wind field
Case 4: (2003 Nov 11) 0349 hr 2.3o
PPI – Reflectivity
Gattatico Bologna
Case 4: (2003 Nov 11) 0349 hr 2.3o
PPI – Doppler Velocity (folding problem)
Gattatico Bologna
Case 4: (2003 Nov 11) 0349 hr 4.8o
PPI – ZDR (bright band)
Case 4: (2003 Nov 11) 0350 hr 2.5o
PPI – Teolo
Doppler velocityReflectivity
measurement
reconstruction
Case 4: (2003 Nov 11) 0345 hr 1.4o
PPI – Radial Velocity Comparison
Gattatico Gattatico
BolognaBologna
Case 4: (2003 Nov 11) 0345 hrWind Field
Comparison with NWP model?
a CD with radar data has been sent to SMHI and wind field information of
several cases have been made available for comparison ...
Conclusion● Analysed a few more new cases.
● All the derived wind fields have been checked by comparing with original measurement and calculating relative deviation of “along-track” component.
● Made initial attempts on triple-Doppler analysis, but need more time to understand Teolo data.
