1. Low-level Wind Analysis and Prediction During B08FDP 2006 Juanzhen Sun and Mingxuan Chen Other contributors: Jim Wilson Rita Roberts Sue Dettling Yingchun Wang Xiaoguang Tan Feng Gao 5th ICMCS - Oct. 31, 2006

2. Outline Description of the analysis system VDRAS Preliminary results from B08FDP 2006 Summary and future work 5th ICMCS - Oct. 31, 2006

3. 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

4. Flow chart of VDRAS analysis procedures 4DVar constrained by a cloud-scale model radial velocity reflectivity u,v,w,T, q r,q c,q v Mesoscale analysis MM5 output Surface obs. VAD analysis 0 min 6 min 12 min Preprocessing and Quality control Integrated display with ANC Background 5th ICMCS - Oct. 31, 2006 4DVar radar data assimilation

5. 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 Kurn ell rms(u dual – u vdras ) = 1.4 m/s rms(v dual – v vdras ) = 0.8 m/s Dual-Doppler verification

6. 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

7. 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

8. Squall line of July 10, 2006 0408 UTC0550 UTC Convective system enhanced by southeast flow

9. VDRAS analysis Wind and Convergence at z = 0.938 kmWind and relative humidity at z = 0.563 km 0408 UTC

10. Severe storm of Aug. 1, 2006 Storm initiated on the mountain and enhanced by low-level boundary interaction 0904 UTC Observed reflectivityAnalyzed convergence Z = 0.9325 km 0925 UTC0947 UTC1007 UTC 1029 UTC

11. 1-hour forecast winds overlaid on observed reflectivity updated every 20 min.

12. 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