1. 5.36 WSN05 Toulouse France, 5-9 September 2005 New Approaches for Nowcasting Winter Road Weather Over a Complex Orography Willi Schmid, meteoradar gmbh Albert Mathis, AnyData ag Urs Keller, MeteoSwiss

2. 5.36 WSN05 Toulouse France, 5-9 September 2005 Winter weather at WSN05 (without fog) Winter road weather1(the present) Winter airport/aircraft weather6

3. 5.36 WSN05 Toulouse France, 5-9 September 2005 Decision making Snow removal / salting Modern Traditional RWIS-stations Weather-forecasts RWIS-stations Weather-forecasts Road-forecast

4. 5.36 WSN05 Toulouse France, 5-9 September 2005 Road forecast 0-2 hours Road-forecast RWIS-station Advection Precipitation Temperature

5. 5.36 WSN05 Toulouse France, 5-9 September 2005 Our Goal To develop fully automated procedures, providing a)Good probability forecasts for critical road parameters b)Good threshold values for correct decisions

6. 5.36 WSN05 Toulouse France, 5-9 September 2005 Issues of this presentation Detection of winter precipitation with radar Precipitation type (rain/snow/black ice) from radar/ground data Radar image extrapolation Cloudiness from temperature measurements Surface temperature forecasts from extrapolated cloudiness Risk forecasts snowfall/black ice/freezing rainwater Road state forecasts from radar and ground data Intervention management

7. 5.36 WSN05 Toulouse France, 5-9 September 2005 Radar-detected precipitation is confirmed on the ground in 65% of all cases. Precipitation on the ground is seen with radar in 35% of all cases Explanation ? Radar and reality Comparison radar – optical sensor on ground

8. 5.36 WSN05 Toulouse France, 5-9 September 2005 Fraction of snow in precipitation KSSG – method (Koistinen/Saltikoff/Schmid/Gjertsen) * * * * * o o o o o o o ** 0 1 P =P = T T T T T

9. 5.36 WSN05 Toulouse France, 5-9 September 2005 Melting layer

10. 5.36 WSN05 Toulouse France, 5-9 September 2005 Validation KSSG method Jan / Feb 2004 KSSG method Radar / Anetz 72 stations Switzerland Temperature/Humidity 10 min Optical sensor PWD11 (Vaisala) 52 stations Canton of Lucerne Rain / snow direct 15 min

11. 5.36 WSN05 Toulouse France, 5-9 September 2005 KSSG and reality Rain predicted Snow predicted Total Rain observed 3311 29.8% 790 7.1% 4101 Snow observed 59 0.5% 6939 62.5% 6998 Total33707729 11099 100% 92.4 % are correct

12. 5.36 WSN05 Toulouse France, 5-9 September 2005 Radar image extrapolation

13. 5.36 WSN05 Toulouse France, 5-9 September 2005 COTREC / Raincast / Raincast+ COTREC radar image extrapolation, ETH 1992 - 1998 Jürg Joss, Li Li, Susanne Mecklenburg Raincast risk forecast rain/hail, ETH, 1999 – 2001 Raincast+ risk forecast snowfall/black ice, 2002...

14. 5.36 WSN05 Toulouse France, 5-9 September 2005 Risk forecast precipitation. 100% 0% Risk

15. 5.36 WSN05 Toulouse France, 5-9 September 2005 Risk forecast snowfall/snow cover

16. 5.36 WSN05 Toulouse France, 5-9 September 2005 Cloudiness Thesis Tobias Grimbacher, IACETH, 2004 Temperature 2m above ground Surface temperature

17. 5.36 WSN05 Toulouse France, 5-9 September 2005 Cloudiness Precipitation Clear Overcast Cloudy

18. 5.36 WSN05 Toulouse France, 5-9 September 2005 + Reliable method Cheap measurements Errors treatable Extrapolation possible Forecasts 1 hour - Dense network required Need more validation Ground temperature extrapolation Based on extrapolated cloudiness Grimbacher et al. To appear in Meteorol. Appl.

19. 5.36 WSN05 Toulouse France, 5-9 September 2005 Projects 1999 – 2005 -... COTREC / RainCastradar image extrapolation Precipitation typerain / snowfall / freezing rain Cloud coverfreezing rainwater Intervention managementIMWS

20. 5.36 WSN05 Toulouse France, 5-9 September 2005 The IMWS project (2003...) IMWS = Intervention management winter service Canton of Lucerne, 2003... Albert Mathis 13 decision criteria Precipitation Clouds Fog Decision go/nogo Hit rate: better than 95 % !

21. 5.36 WSN05 Toulouse France, 5-9 September 2005 Thank You 5.36 WSN05 Toulouse France, 5-9 September 2005