Reference: Jung Y., G. Zhang, and M. Xue, 2008: Assimilation of simulated polarimetric

1. Assimilation of simulated polarimetric radar data for a convective storm using the ensemble Kalman filter. Part I: Observation operators for reflectivity and polarimetric variables. Reference: Jung Y., G. Zhang, and M. Xue, 2008: Assimilation of simulated polarimetric radar data for a convective storm using the ensemble Kalman filter. Part I: Observation operators for reflectivity and polarimetric variables. Mon. Wea. Rev., 136, 2228–2245. Report : Prudence Chien

2. OUTLINE • The model and convection storm simulations • The observation operators and simulation of observations • Application to convections storms • Summary and conclusions

3. OSSE(Observing System Simulation Experiment)觀測系統模擬實驗 將真實觀測到的環境場資訊，ex：sounding等，放到數值模式裡建立虛擬的真實大氣情況與(雷達)觀測資料。再配合實驗的目的修改模式或同化方法，重新預報，最後和虛擬真實大氣做比較，以瞭解各實驗的預報能力。 吳子榆, 2008:利用EnKF同化雙偏極化雷達資料PARTⅡ:雙偏極化資料針對對流風暴分析之影響

4. The model and convection storm simulations • Advanced Regional Prediction System (ARPS) Center for Analysis and Prediction of Storms, University of Oklahoma, 1989 • Compressible • Nonhydrostatic • Ice microphysics scheme -> LFO83

5. http://www.caps.ou.edu/ARPS/arpsoverview.html

6. The observation operators and simulation of observations • The shape, orientation, and drop size distribution of hydrometeors • Melting ice (snow-hail) model • Observation operators

7. a. The shape, orientation, and drop size distribution of hydrometeors (Straka et al. 2000)

8. a. The shape, orientation, and drop size distribution of hydrometeors (Lin et al. 1983) get Minor axis Major axis D:equivalent diameter(mm) By an equivalent model (Green 1975) r≡ Fit a polynomial function (Zhang et al. 2001)

9. b. Melting ice (snow-hail) model • Fraction Set Fmax = 0.5 Fqr : mixing ratio of rainwater in the mixture form (1 – Fqr) : mixing ratio of rainwater in the pure water form Snow melting fw = 0 fs = 1 fw = 1 fs = 0 • Density • Dielectric constant Maxwell–Garnett mixing formula (Maxwell-Garnett 1904)

10. c. Observation operators x : hydrometeor type fa , fb : backscattering amplitudes

11. c. Observation operators rain Minor-axis Major-axis Rain-snow Rain-hail Major-axis Major-axis Minor-axis Minor-axis

12. c. Observation operators WSR-88D radar λ = 10.7 cm Rain reflectivities Hydrometeor reflectivities Total reflectivities

13. c. Observation operators ZDR: differential reflectivity Shape of hydrometeor : axis & size Zdp:reflectivity difference Mixed-phase precipitation concentration KDP :specific differential phase Linearly proportional to the rain fall rate

14. Application to convections storms • 2D Squall-line case • 3D Supercell storm

15. a. Squall-line case

17. LI : Linear interpolation model (Jung et al. 2005) MI : Melting ice model

19. b. Supercell storm

21. qr ZH ZDR qs KDP qh

22. Summary and conclusions • The purpose of develop radar operators1. Assimilating the corresponding measurements into storm-scale numerical models2. Verify model predictions against radar observations • A new melting modelAssumes a function for the water fraction based on known rainwater, snow, and hail mixing ratios=> Improve microphysics schemes

23. Summary and conclusions • Convective storms • Overestimate reflectivity1. Neglected non-Raleigh scattering2. Fixed DSD intercept parameter of hail3. Lack of raindrop breakup

24. Thanks for your attention.

26. EnKF Zhiyong Meng and Fuqing Zhang : Comparing WRF-based EnKF with 3DVar for an MCV Event during BAMEX

27. OSSEs 黃國禎, 2007:使用系集卡曼濾波器同化都卜勒雷達資料之研究