1. Radars in the Mountains Germann, MCH

2. Atmosphere is very layered 3 flow regimes evident but really 5? 5 layers? 1234512345 Vertical profile of reflectivity

3. Orographic Precipitation Rain shadow

4. FOEHN, no rain H3km The Alps Lee Side Suppression

5. Two Conceptual Models of Orographic Precipitation Medina and Houze, 2003

6. Precipitation is on the flow when the flow is blocked. Radial velocity Reflectivity

7. Precipitation is on the mountain crest when the flow is “up and over”.

8. A little of both!

9. Precipitation is very sensitive to evaporation and sublimation – no precipitation reached the ground

10. Melting is obvious but what is magical about 20 dBZ?

11. Snow processes can be very shallow!

12. Examples of very shallow precipitation

13. VPR/Process Classification Hourly sampling/manual classification

14. Summary Shallow Weather –Focus on drizzle as an example to explain detectability and measurability –Observability is a function of the radar too (MDS, beamheight, beamwidth) –A few simple but key calculations to explain (not calibration, not attenuation) –A little insight into “radar meteorology” A few case examples –Drizzle, snow, lake effect snow, orographic

15. Freezing Level and Mountain Sited Radars Time-Height Temperature Freezing Level from Radiosondes March 2008 Payerne July 2008 Payerne Most of the time, the radar sees snow!

16. Erzgebirge Ore mountains, grey Doppler No rain 1h accumulation No rain Accumulations

17. Stable Case: Blocked Flow from South North South ALPS Precipitation on plains, Italy Flow is blocked, flow is towards the south MAP IOP-8 Medina and Houze, 2003

18. Radial Velocity - Blocked Flow Medina and Houze, 2003

19. Unstable Case: Up and Over Precipitation is on the first range No blocked flow. Flow is from the south Medina and Houze, 2003

20. Radial Velocity – Up and Over Medina and Houze, 2003

21. Lee Side Troughing On a very small terrain feature

22. Southern Ontario is relatively flat. Elevations rise from about 200m on Lake Huron to about 400m just south of Georgian Bay. Lake Huron Lake Ontario Lake Erie Georgian Bay Topography of Southern Ontario

23. Average of six GOES images over a 3-hour period Moderate WSW flow Dissipation of thin SC cloud in downslope flow SC cloud forming beneath an inversion at 1500 m above ground Dissipation of Clouds in a SW Flow

24. Topography of Southern Ontario Niagara Escarpment Average of six GOES images over a 3-hour period