Low-level Wind Analysis and Prediction During B08FDP 2006

Juanzhen Sun and Mingxuan Chen

Other contributors:Jim WilsonRita RobertsSue DettlingYingchun WangXiaoguang TanFeng Gao

5th ICMCS - Oct. 31, 2006

Outline

• Description of the analysis system VDRAS• Preliminary results from B08FDP 2006• Summary and future work

5th ICMCS - Oct. 31, 2006

What is VDRAS?

5th ICMCS - Oct. 31, 2006

• Continuously cycled 4D-Var system of a cloud-scale model

• Assimilate both radial velocity and reflectivity

• Can be updated every 12 min.

• Produce analyses of wind, temperature perturbation,

relative humidity, and some microphysics

• Has been implemented in real time at more than ten

locations

Variational Doppler Radar Analysis System

Flow chart of VDRAS analysis procedures

4DVar constrained by a cloud-scale model

radial velocityreflectivity

u,v,w,T, qr,qc ,qv

Mesoscale analysisMM5 output

Surface obs. VAD analysis

0 min 6 min 12 min

Preprocessing andQuality control

Integrated display with

ANC

Background

5th ICMCS - Oct. 31, 2006

4DVar radar data assimilation

VDRAS Verification from previous studies

• ACARS (Sun and Crook 2000)

• Dual-Doppler (Crook and Sun 2004)

• Research aircraft (Sun and Crook 1998)

5th ICMCS - Oct. 31, 2006

Cpol

Kurnell

rms(udual – uvdras) = 1.4 m/s

rms(vdual – vvdras) = 0.8 m/s

Dual-Doppler verification

VDRAS implementation in Beijing

• Domain size: 100X100X14 grid points with a 3kmx3kmx375m resolution assimilating BJRS and TJRS data

• Run on a 2-processor Dell workstation

• Take ~ 20 min for each analysis (with a 12 min assimilation window) plus a 1-hour forecast

5th ICMCS - Oct. 31, 2006

Special Issues for VDRAS in Beijing

5th ICMCS - Oct. 31, 2006

• Complex terrain

• Radar data quality - AP problem - Radars only operate in storm

mode • Dense surface network in

Beijing but sparse outside

• MM5 analysis only twice a day

Squall line of July 10, 2006

0408 UTC 0550 UTC

Convective system enhanced by southeast flow

VDRAS analysis

Wind and Convergence at z = 0.938 km Wind and relative humidity at z = 0.563 km

0408 UTC 0408 UTC

Severe storm of Aug. 1, 2006

Storm initiated on the mountain and enhanced by low-level boundary interaction

0904 UTC

Observed reflectivity Analyzed convergenceZ = 0.9325 km

0925 UTC0947 UTC1007 UTC1029 UTC

1-hour forecast winds overlaid on observed reflectivityupdated every 20 min.

Summary and Future Work

5th ICMCS - Oct. 31, 2006

• VDRAS was able to run robustly at BMB, assimilating radial velocity and reflectivity from BJRS and TJRS• VDRAS produced analyses on a 300kmx300km domain every 20

min.• Preliminary case studies indicated that VDRAS produced

reasonable analysis even with the complex terrain• Further studies are needed to verify VDRAS analysis using independent data• Surface wind (2 meter above ground) forecast product will be

generated for water sports venues