Impact of Doppler Radar Observations on the EnKF Analysis of a Developing MCS

1. Impact of Doppler Radar Observations on the EnKF Analysis of a Developing MCS Mike Coniglio David Dowell Lou Wicker Dave Stensrud National Severe Storms Laboratory EnDA Workshop, Marble Falls TX

2. Motivation • Limited real-data EnKF experiments • Does EnKF work with a messy convective event? • Obstacles to getting robust storm-scale analyses using WSR-88D data? • Refl-only vs. refl&vel assimilation? • Build catalog of cases from diff convective modes to prove storm-scale EnKF concept • Start with the 11-12 June 2003 MCS EnDA Workshop, Marble Falls, TX

3. 11-12 June 2003 MCS 2129z 2144z 2159z 2214z 2229z 2243z 2258z 2313z 2328z 2343z 2357z 0013z 0028z 0043z 0058z 0112z 0127z 0142z 0207z 0221z 0236z 0251z 0306z 0321z EnDA Workshop, Marble Falls, TX

4. 11-12 June 2003 MCS EnDA Workshop, Marble Falls, TX

5. Configuration of Experiments • NCOMMAS • ne=20-50 members • ~ 400 km by 400 km domain • Dx,y=2-3 km in model and obs analysis • Data assimilated every 1-5 min for various 45-90 min periods • Modified & perturbed OUN sounding • LFO ice with various slope/intercept parameters • Only reflectivity assimilated initially EnDA Workshop, Marble Falls, TX

6. Sense from Initial Experiments • Solutions very sensitive to initial sounding • Too little CIN – noise & spurious storms • Need to set missing dBZs to a low value (0) • Too much CIN – storms die after assimilation • Storms/cold pool structures during assim. too small & too weak, not persistent • Perhaps REFL-only assimilation not feasible? • Try using reflectivity & radial velocity • Too much convection in ground clutter • Automated velocity unfolding and ground clutter removal implemented EnDA Workshop, Marble Falls, TX

7. Runs after 3-4 months testing • Runs are stable with good representation of two main clusters • but getting too much convection in between main storms Obs Analysis EnKF Analysis EnDA Workshop, Marble Falls, TX

8. Runs after 3-4 months testing • Too much ground clutter getting through? • No! Anomalous cold pool is an issue: EnDA Workshop, Marble Falls, TX

9. Dowell 8 May 2003 experiment • What if TH isn’t updated with a velocity ob? EnDA Workshop, Marble Falls, TX

10. No update of TH with Vel • Anomalous cold pool gone: • BUT…….. EnDA Workshop, Marble Falls, TX

11. PROBLEM • Noticed storm/cold pool growth slow • Increase in initial sounding variability and bubbles didn’t help much • dBZ and QR too low in low levels! EnDA Workshop, Marble Falls, TX

12. PROBLEM • dBZ and QR too low in low levels EnDA Workshop, Marble Falls, TX

13. Lack of Low-Level Reflectivity • Could explain why updraft/cold pool structures too transient • Microphysics or obs problem? • What if reflectivity is withheld in precipitating areas? • Don’t assimilate reflectivity < 15 dBZ • LFO large hail setting not appropriate? -Change to graupel/hail mixture • Change raindrop size distribution • Are there more problems with using velocity? • Don’t assimilate radial velocity at all EnDA Workshop, Marble Falls, TX

14. no assimilation of reflectivity > 15 dBZ, more graupel • Reflectivity important for maintaining storms! EnDA Workshop, Marble Falls, TX

15. Fewer but larger raindrops EnDA Workshop, Marble Falls, TX

16. Fewer but larger raindrops EnDA Workshop, Marble Falls, TX

17. Fewer but larger raindrops EnDA Workshop, Marble Falls, TX

18. No assimilation of velocity EnDA Workshop, Marble Falls, TX

19. No assimilation of velocity EnDA Workshop, Marble Falls, TX

20. Where to go from here • Nail down anomalous bubble problem • Explore microphysics impacts • Thorough comparison of refl only vs refl & vel experiments • New ways to initialize ensemble/maintain spread • Try new cases from “scratch” EnDA Workshop, Marble Falls, TX