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.