1. Mountain wave structures occurring within a major orographic precipitation event: Part 2: Observed and Modeled Precipitation Fields Matt Garvert, Brad Smull and Cliff Mass IMPROVE-Meeting 13 July 2005 Photo by Greg Thompson- http://www.inclouds.com

2. Part-2 Discussion Topics Analysis of precipitation structures over complex terrain using dual-Doppler radar. Utilize MM5 to assist in explaining structures in reflectivity –Large scale (> 20-km) over mean crest –Small scale (< 20-km) over windward slopes

3. Observed Mean E-W Cross Section 32-36 >36 28-32 24-28 20-24 16-20 12-16 08-12 04-08 dBZ 3 2 1

4. P3-Reflectivity and MM5-Snow field 2300-0100 UTC 32-36 >36 28-32 24-28 20-24 16-20 12-16 08-12 04-08 dBZ Snow (g kg -1 ) MB

5. SBAND - Reflectivity Reflectivity maximum between 4-5 km is attributed to growth of dendrites which are then advected to lee of mountain barrier.

6. MM5-w (m s -1 ) Wave-like behavior in MM5-Kinematic and CLW Fields 32-36 >36 28-32 24-28 20-24 16-20 12-16 08-12 04-08 dBZ MM5-CLW (g kg -1 ) 23 -01 UTC

7. MM5-w (m s -1 ) 2200 -0030 UTC

8. MM5-Clw (g kg -1 ) 2200 -0030 UTC

9. Distance from Crest (km) IB UW SPL MB Looking closer at leg-2 Latitude (Deg) Distance from Crest (km) 0-250 250-500 500-750 750-1000 1000-1250 1250-1500 1500-1750 1750-2000 2000-2250 >2250 Elevation (m) SPL S N

10. U-Wind V-Wind W-Wind CLW (m s -1 ) (g m -3 ) (km) Elevation MM5 1.33-km P3 In situ P3 Doppler 0 10 20 30 40 50 60 70 80 90 100 110 Distance (km) Latitude (Deg) 44.00 44.09 44.18 44.27 44.36 44.45 44.54 44.63 44.72 44.81 44.90 44.98 N S JAS-Garvert (2005)

11. 0 10 20 30 40 50 60 70 80 90 100 110 Distance (km) N S Dual-Doppler v-wind 32-36 36-40 28-32 24-28 20-24 16-20 12-16 08-12 <08 V-Wind (m s -1 ) >40

12. 0 10 20 30 40 50 60 70 80 90 100 110 Distance (km) N S w (m s -1 ) positive negative Dual-Doppler v-wind and w 32-36 36-40 28-32 24-28 20-24 16-20 12-16 08-12 <08 V-Wind (m s -1 ) >40

13. 0 10 20 30 40 50 60 70 80 90 100 110 Distance (km) N S Dual-Doppler dBZ and w 32-36 >36 28-32 24-28 20-24 16-20 12-16 08-12 04-08 dBZ w (m s -1 ) positive negative

14. 0 10 20 30 40 50 60 70 80 90 100 110 Distance (km) N S Dual-Doppler dBZ and MM5-w 32-36 >36 28-32 24-28 20-24 16-20 12-16 08-12 04-08 dBZ w (m s -1 ) positive negative

15. 0 10 20 30 40 50 60 70 80 90 100 110 Distance (km) Latitude (Deg) 44.00 44.09 44.18 44.27 44.36 44.45 44.54 44.63 44.72 44.81 44.90 44.98 N S Height (km) 0.2-0.4 0.4-0.6 > 0.6 MM5 Cloud Liquid Water (g kg -1 )

16. 0 10 20 30 40 50 60 70 80 90 100 110 Distance (km) Latitude (Deg) 44.00 44.09 44.18 44.27 44.36 44.45 44.54 44.63 44.72 44.81 44.90 44.98 N S Height (km) 0.2 0.6 0.4 0.8 1.0 1.2 1.4 1.6 0.2-0.4 0.4-0.6 > 0.6 MM5 Cloud Liquid Water (g kg -1 ) snow MM5-Precip (g kg -1 )

17. 0 10 20 30 40 50 60 70 80 90 100 110 Distance (km) Latitude (Deg) 44.00 44.09 44.18 44.27 44.36 44.45 44.54 44.63 44.72 44.81 44.90 44.98 N S Height (km) 0.2 0.4 0.2 0.6 0.4 0.8 1.0 1.2 1.4 1.6 0.2-0.4 0.4-0.6 > 0.6 MM5 Cloud Liquid Water (g kg -1 ) snow graupel MM5-Precip (g kg -1 )

18. 0 10 20 30 40 50 60 70 80 90 100 110 Distance (km) Latitude (Deg) 44.00 44.09 44.18 44.27 44.36 44.45 44.54 44.63 44.72 44.81 44.90 44.98 N S Height (km) 0.2 0.4 0.2 0.6 0.4 0.8 1.0 1.2 1.4 1.6 0.2 0.4 0.2-0.4 0.4-0.6 > 0.6 MM5 Cloud Liquid Water (g kg -1 ) snow graupel rain MM5-Precip (g kg -1 )

19. Smoothed 1.33-km-Terrain IB SPL MB Willamette Valley Cascade Crest Effect of Terrain Resolution on Precipitation Totals Terrain (m) 1.33-km Terrain IB SPL MB 250 500750100012501500175020002250>25000 Willamette Valley Cascade Crest

20. 1.33-km Precip S N Precip (mm) 0 10 20 30 40 50 60 70 80 90 100 110 Distance (km) Elevation (km) Accumulated Precipitation from 22-01 UTC

21. 1.33-km Precip 1.33-km Smooth Precip 6-15% 6-15% increase in accumulated precipitation over windward slopes S N 0 10 20 30 40 50 60 70 80 90 100 110 Distance (km) Precip (mm) Accumulated Precipitation from 22-01 UTC Elevation (km)

22. Willamette Valley Coast SPOL Longitude (Deg) Latitude (Deg) S N W E Height (m)

23. Willamette Valley Coast Longitude (Deg) Latitude (Deg) S N W E Height (m) SPOL

24. Conclusions Interaction of two distinct air streams; low-level barrier-parallel airflow and upper level ‘flow-over’ regime resulted in heavy precipitation over windward slopes of Cascades. Larger-scale mountain wave atop Cascade-crest produced enhanced snow field which was subsequently advected to lee slopes. Low-level barrier parallel flow interacted with the complex terrain of windward slopes producing waves which enhanced accretional processes and QPF (7-15%). Impact of coastal mountains was spatially focused, and evidently not related to wave-like behavior over windward slopes of Cascades (not shown).

25. Future Work Improve derivation of Doppler vertical-velocity by altering boundary conditions (similar to Bousquet and Smull 2003). Simulate case with WRF model (improved numerics and physics) with Thompson-microphysics. Examine additional cases that have been seen to possess similar kinematic structures e.g., November 29th-30th and possibly MAP-IOP8 case. Utilize the in situ microphysical observations to document and quantify the effect of smaller scale (>20 km) waves on the snow and CLW fields.

26. MM5-Accumulated Precipitation EW 1.33-km Precip

27. EW 1.33-km Smooth Precip MM5-Accumulated Precipitation

28. 1.33-km Precip 1.33-km Smooth Precip 6- 15% Increase in accumulated precipitation by 6- 15% over windward slopes MM5-Accumulated Precipitation

29. Observed E-W Cross-Section Wind SpeedW-DIR

30. Willamette Valley Coast SLE Longitude (Deg) Latitude (Deg) S N W E Height (m)

31. Willamette Valley Coast SLE Longitude (Deg) Latitude (Deg) S N W E Height (m)

32. 0 10 20 30 40 50 60 70 80 90 100 110 Distance (km) Latitude (Deg) 44.00 44.09 44.18 44.27 44.36 44.45 44.54 44.63 44.72 44.81 44.90 44.98 N S Height (km) -0.2 -0.4 -0.6 -0.8 -1.2 -1.4 -1.6 <-1.8 >1.8 1.6 1.4 1.2 1.0 0.8 0.6 0.4 0.2 0.0 W (m s -1 )

33. Average QPF E-W EW

34. THE END Thanks to: Dave Ovens, Stacy Brodzik, Socorro Medina, Amy Haase, Dale Durran, Lucas Harris, Brian Colle, John Locatelli and others.