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New Approaches for Nowcasting Winter Road Weather Over a Complex Orography

New Approaches for Nowcasting Winter Road Weather Over a Complex Orography Willi Schmid, meteoradar gmbh Albert Mathis, AnyData ag Urs Keller, MeteoSwiss. Decision making Snow removal / salting. Modern. Traditional. Weather-forecasts. RWIS-stations. Weather-forecasts. RWIS-stations.

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New Approaches for Nowcasting Winter Road Weather Over a Complex Orography

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  1. New Approaches for Nowcasting Winter Road Weather Over a Complex Orography Willi Schmid, meteoradar gmbh Albert Mathis, AnyData ag Urs Keller, MeteoSwiss

  2. Decision making Snow removal / salting Modern Traditional Weather-forecasts RWIS-stations Weather-forecasts RWIS-stations Road-forecast

  3. Road forecast 0-2 hours • Advection • Precipitation • Temperature RWIS-station Road-forecast

  4. Our Goal • To develop fully automated procedures, providing • Good probability forecasts for critical road parameters • Good threshold values for correct decisions

  5. 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

  6. Radar and reality Comparison radar – optical sensor on ground • 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 ?

  7. Fraction of snow in precipitation KSSG – method (Koistinen/Saltikoff/Schmid/Gjertsen) P= 1 0 T * * T * T * * T T * * o o o o o o o

  8. Melting layer

  9. Validation KSSG method Jan / Feb 2004 • Optical sensor • PWD11 (Vaisala) • 52 stations • Canton of Luzerne • Rain / snow direct • 15 min • KSSG method • Radar / Anetz • 72 stations • Switzerland • Temperature/Humidity • 10 min

  10. KSSG and reality 92.4 % are correct

  11. Radar image extrapolation

  12. 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 ...

  13. . Risk forecast precipitation Risk 100% 0%

  14. Risk forecast snowfall/snow cover

  15. Cloudiness Thesis Tobias Grimbacher, IACETH, 2004 • Temperature 2m above ground • Surface temperature

  16. Cloudiness Precipitation Overcast Cloudy Clear

  17. Ground temperature extrapolation Based on extrapolated cloudiness • + • Reliable method • Cheap measurements • Errors treatable • Extrapolation possible • Forecasts 1 hour • - • Dense network required • Need more validation Grimbacher et al. To appear in Meteorol. Appl.

  18. Projects 1999 – 2005 - ... • COTREC / RainCast radar image extrapolation • Precipitation type rain / snowfall / freezing rain • Cloud cover freezing rainwater • Intervention management IMWS

  19. 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 % !

  20. References www.meteoradar.ch www.sirwec.org

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