Development and Research of GSI- based Var/EnKF/EnVar/ Hybrid System to Assimilate Radar ObservaBons for ConvecBve Scale NWP

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1 Development and Research of GSI- based Var/EnKF/EnVar/ Hybrid System to Assimilate Radar ObservaBons for ConvecBve Scale NWP Xuguang Wang School of Meteorology University of Oklahoma, Norman, OK D Acknowledgement Yongming Wang (OU), Aaron Johnson (OU) Jacob Carley (NOAA/NCEP) Lou Wicker (NOAA/NSSL) Buleprints for Next-Generation Data Assimilation System Workshop Mar. 8-10, 2016, Boulder, CO 1

2 Challenges for next generation DA system for NWP Future generation DA system should be capable of producing accurate multiscale analysis through effectively assimilating observations from various in-situ and remote sensing platforms in computationally efficient manner. 2

3 GSI-based Var/EnKF/EnVar/Hybrid for global and regional modeling systems GSI- based Var/EnKF/3/4DEnVar/ Hybrid GFS WRF- NMMB WRF ARW Hurricane- WRF (HWRF) GSI based Hybrid was implemented operationally at NCEP since Significant improvement from both 3DEnVar and 4DEnVar hybrid was found for GFS forecast in various experiments (e.g., Hamill et al. 2011; Wang et al. 2013; Wang and Lei 2014; Kleist and Ide 2015; Mahajan et al. 2016) R&D are being made for high resolution regional models. 3

4 MoBvaBon for GSI- based Var/EnKF/EnVar/Hybrid DA Development and Research for ConvecBve Scales ConvecBve scale analysis and forecasbng is a mulb- scale problem, requiring an accurate esbmate of both the synopbc/mesoscale environment and the convecbve scale details. ConvecBve scale observabons (i.e., radar, satellite radiances) require unique observabon operators that are oten complex and nonlinear. Inclusion of addibonal state variables (e.g., hydrometeors, W) are required. Accurate cross- variable covariance is especially important. Comparison study among Var, EnKF, 3DEnVar, 4DEnVar and Hybrid for convecbve scales including both complex cases with mulbple storm modes and interacbons in a largely heterogeneous environment, and isolated tornadic storms is sbll limited. 4

5 Development of GSI based Var/EnKF/EnVar/Hybrid for convecbve scales GSI- based Var, EnKF, 3DEnVar, 4DEnVar and Hybrid are extended to work with convecbon- resolving models such as WRF ARW (Johnson et al. 2015; Wang et al. 2016). VerBcal velocity and hydrometeor control variables are added. Radar radial velocity and reflecbvity observabon operators are implemented. For direct assimilabon of reflecbvity observabons, various control variables were developed, derived, and implemented in GSI EnVar (Wang et al. 2016). Capability to use storm scale perturbabons to treat model errors is added. 5

6 GSI- based EnKF: Assimilate mulbscale obs. for various complex cases (Johnson et al. 2015, MWR) Forecasts inibalized from mulb- scale analyses are more skillful for GSI- based EnKF than GSI3DVar. DiagnosBcs show that all scales of mobon contribubng to the convecbve evolubon are be`er analyzed with GSI- based EnKF due to flow dependent, cross variable ensemble covariances. Radar data assimilabon improves forecast skill for 4-5h for GSI based EnKF but only 1h for GSI3DVar. Scattered cellular convection Supercells Mesoscale Convective Systems u 6

7 GSI- based EnKF: Real- Bme DA and forecasbng in support of the PECAN field campaign 06 July MCS and CI 1-day forecast MCS in SE South Dakota and NE Nebraska. Bores and CI developed out ahead of the leading convecbon in western Iowa. Both were captured in the MAP ensemble. Very successful mission for the PECAN campaign led by strong forecast guidance. Johnson and Wang (2016) 7

8 GSI based EnVar: Wang et al

9 GSI based EnVar: Wang et al standard 9

10 GSI based EnVar: May 8 th 2003 OKC Tornadic Supercell Path of the May 8, 2003 Moore-South OKC Area Tornado 22:00 UTC 08 May An isolated supercell case that produced F- 4 intensity tornadoes in Moore and Oklahoma City (OKC) during about UTC. Supercell maintained well beyond 2300 unbl about 2400 UTC. 10

11 Experiment design Wang et al Model: WRF- ARW 2km ObservaJon: radar radial wind and reflecbvity from KTLX IC and LBC ensemble: A 45- member ensemble downscaled from a mesoscale ensemble at 2100 UTC. 5 min 1 hour forecast 21:00 22:00 23:00

12 GSI based 3DVar: analysis and 1h forecast from 2200UTC Ref and vorbcity at 1 km W at 4 km 12

13 GSI based EnVar: analysis and 1h forecast from 2200UTC Ref and vorbcity at 1 km W at 4 km 13

14 Prob. fcst. starbng 2200 UTC: GSI based EnVar 14

15 EnVar with various hydrometeor control variables m/s m/s m/s 15

16 K Factors that impact storm evolubon associated with different control variables 5km Qg analysis (g/kg) 5km Qg analysis (g/kg) 5km Qg analysis (g/kg)

17 GSI EnVar extended with different microphysics schemes for reflectivity assimilation 2200 UTC 2215 UTC 2230 UTC 2245 UTC WSM6 Thompson Obs. from Yussouf

18 Summary and Challenges Summary q GSI- based Var/EnKF/EnVar/Hybrid data assimilabon system is further developed for convecbve scale radar data assimilabon. q A new control variable was developed and implemented to assimilate nonlinear reflecbvity observabons in EnVar. q Experiments for complex mesoscale system and isolated supercell both show improved analysis and forecast by EnKF and EnVar. Challenges q Complementary use of ground based and space borne remote sensing obs. (e.g., ground based radar, satellite radiances) q EffecBve methods to treat/sample model error in ensemble background q Elegant methods to assimilate observabons in a system that resolves mulbple scales (including treatment of sampling errors for different scales). q Dealing with nonlinearity, parbcle filter q Efficient computabon associated with high resolubon global/large domain model, high resolubon observabons and large ensemble 18