Update on the Northwest Regional Modeling System

1. Update on the Northwest Regional Modeling System Cliff Mass, Dave Ovens, Jeff Baars, Mark Albright, Phil Regulski, Dave Carey University of Washington

3. The current model domains 36-12-4/1.33 km

4. Major Changes and Improvements • Beginning with the December 31, 2009 0000 UTC run, the WRF-GFS, our flagship system, has switched to the latest version of WRF (3.1.1.) • Bug fixes in several of parameterizations we use. • Better microphysics (should get start of light rain better). • More boundary layer options (a major problem) • More stable. • But as we will see, the new system has created some problems too.

5. Added an Operational Ultra High Resolution 1.33 km Nest to Our Current 36 km/12 km/4 km system • Western WA only • Once a day (0000 UTC cycle) to 36 h • Attempt to answer questions: • What is the payoff in getting the land-water boundaries and smaller scale terrain much better (4-km hardly has Puget Sound!) • Does ultra high resolution improve objective verification or subjective structures?

6. 4 km 1.3

7. 1.3 Land Use 4 km

11. Precip Verification

12. Wind Direction

13. Future Evaluation • Beginning intensive objective verification • Improving boundary layer schemes, surface drag, and surface physics may preferentially help 1.3 km (more later)

14. The Greenest Computer Facility in the U.S.? • We have roughly 150 processors for the high resolution and ensemble runs • Approximately, 200 Terabytes of storage. • Needs very little air conditioning and we had no trouble getting through the 103F heat last summer. • Why?

15. Suck in Cool Outside Air!

16. Blow the hot air out!Why AC when you can dump it?

17. Three big fans on each enclosure!

19. But is it better?Nighttime Temps are Fine

20. The new system is too cold during the day on average.

21. But why?Problem over the Interior.

22. The Problem: Where There is Snow on the Ground and High ElevationThe Problem Is Probably in the Land Surface Model

23. Model Wack a Mole!

24. Wind Direction Errors: Stable and Generally Better than NWS 12-km NAM

25. Wind Speed is Another Issue: UW WRF too strong, NWS NAM too Weak

26. A Major Problem Has Been Surface Winds Over Land • Winds too strong over land • Winds too geostrophic over land • Winds over land and water too similar

29. Fixing the Problem • No magic bullet in testing various planetary boundary layer (PBL) schemes • Recently, we tried two approaches that are very promising: • Increasing the friction veloc (ustar) in the PBL. Essentially adds low-level drag. • Decreasing vertical diffusion in the model (less vertical mixing of high momentum air down to the surface).

31. Changing Surface Drag Standard Low Diffusion

32. The Fix • We are testing these new approaches singly and together. • Verification statistics show we can reduce the wind bias without harming other parameters. • Next month we should put the fix into place and expect a radical improvement in the wind bias.

33. Testing the Fixes: Ustar *1.5

34. 3 weeks of statistics

35. A Lot More To Talk About But no Time • A high resolution local data assimilation system (EnKF) is being tested and developed. • Very high quality local analyses and very good short-term forecasts should be available this year. • We are testing this system for use with the new coastal radar: may see much better local short-term forecasts if this works.

36. The End