1. Detailed Structure of Moist, Sheared, Statically Stable Orographic Flow Socorro Medina 1, Robert Houze 1, and Nicole Asencio 2 29 th International Conference on Alpine Meteorology, Chambéry, France, 4-8 June 2007 1 University of Washington, Seattle, USA; 2 Météo-France, CNRS, Toulouse, France MAP IOP8 - 00 UTC 21 Oct

2. Detailed Structure of Moist, Sheared, Statically Stable Orographic Flow Socorro Medina 1, Robert Houze 1, and Nicole Asencio 2 29 th International Conference on Alpine Meteorology, Chambéry, France, 4-8 June 2007 1 University of Washington, Seattle, USA; 2 Météo-France, CNRS, Toulouse, France MAP IOP8 - 00 UTC 21 Oct N 2 (x10 -4 s -2 ) Height (km)

3. OBJECTIVES Examine flow and shear layer at low- levels Misplacement of precipitation in numerical simulations The nature of observed turbulent motions

4. OBJECTIVES Examine flow and shear layer at low- levels Misplacement of precipitation in numerical simulations The nature of observed turbulent motions

5. (b) Orography (km) S-Pol radial velocity (m s -1 ) for elevation angle of 3.8° 00 UTC 21 Oct 1999 32 24 16 8 0 -8 -16 -24 -32 4.0 3.5 3.0 2.5 2.0 1.5 1.0 0.5 0.0

6. Constant Elevation Angle Scanning Z1 < Z2 Range

7. (b) Orography (km) S-Pol radial velocity (m s -1 ) for elevation angle of 3.8° 00 UTC 21 Oct 1999 32 24 16 8 0 -8 -16 -24 -32 4.0 3.5 3.0 2.5 2.0 1.5 1.0 0.5 0.0 RANGE  ALTITUDE

8. (b) Orography (km) S-Pol radial velocity (m s -1 ) for elevation angle of 3.8° 00 UTC 21 Oct 1999 4.0 3.5 3.0 2.5 2.0 1.5 1.0 0.5 0.0 32 24 16 8 0 -8 -16 -24 -32 Low-level flow

9. (b) Orography (km) S-Pol radial velocity (m s -1 ) for elevation angle of 3.8° 00 UTC 21 Oct 1999 4.0 3.5 3.0 2.5 2.0 1.5 1.0 0.5 0.0 32 24 16 8 0 -8 -16 -24 -32 Mid-level flow

10. (b) Orography (km) S-Pol radial velocity (m s -1 ) for elevation angle of 3.8° 00 UTC 21 Oct 1999 4.0 3.5 3.0 2.5 2.0 1.5 1.0 0.5 0.0 32 24 16 8 0 -8 -16 -24 -32 Upper-level flow MAP IOP8 - 00 UTC 21 Oct

11. (b) S-Pol radial velocity (m s -1 ) for elevation angle = 3.8° in a rectangular azimuth-range plot 32 24 16 8 0 -8 -16 -24 -32 00 UTC 21 Oct 1999 360

12. OBJECTIVES Examine flow and shear layer at low- levels Misplacement of precipitation in numerical simulations The nature of observed turbulent motions

13. Precipitation accumulation during 21 Oct Meso-NH simulation of Asencio and Stein (2006)  Common thread in simulations Rain-gauge observations Frei and Häller (2001)

14. Observed S-Pol mean radial velocity (m s -1 ) ( 00-09 UTC 21 Oct) Simulated – Asencio and Stein 32241680-8-16-24-32

15. Observed Milan sounding at 00 UTC 21 Oct Simulated OBS SIM (e)

16. OBJECTIVES Examine flow and shear layer at low- levels Misplacement of precipitation in numerical simulations The nature of observed turbulent motions

17. Houze and Medina (2005) Conceptual model of orographic enhancement of precipitation by turbulent small-scale cells

18. S-Pol time-averaged variables and std deviation (19 UTC 20 Oct – 01 UTC 21 Oct) Radial velocity (every 4 m s -1 in solid contours) STD deviation radial velocity (m s -1 ; color) Topography (at range = 20 km) Terrain Height (km)

19. S-Pol time-averaged variables (19 UTC 20 Oct – 01 UTC 21 Oct) Reflectivity (dBZ; color) Topography (at range = 20 km) Terrain Height (km) Radial velocity (every 4 m s -1 in solid contours)

20. Why kind of turbulence are we observing? DOW Radar observations Radial velocity (m s -1 ) Shear (m s -1 km -1 )

21. Radar observations of Kevin-Helmholtz billows in mid-latitude precipitating system Radial velocity (m s -1 ) Chapman and Browning (1997) Shear (m s -1 km -1 )

22. CONCLUSIONS Three flows: synoptically driven upper-level flow, barrier-scale mid-level jet, and valley-scale low-level jet In comparison between observed and simulated precipitation: fundamental to evaluate detailed structure of windward flow In obs: Shear + Terrain = Turbulent flow and enhanced precipitation