Titelfoto auf dem Titelmaster einfügen Deutscher Wetterdienst IMPROVING RELIABILITY AND SENSITIVITY OF A LASER SNOW DEPTH GAUGE Eckhard Lanzinger and Manfred Theel, Deutscher Wetterdienst (DWD)

DWD / E. Lanzinger TECO-2010, 30. August – 1. September 2010, Helsinki, Finland Comparison of ultrasonic and laser snow depth gauges Experimental setup  Campbell SR50G (ultrasonic) ■ sonic cone with angle of aperture: 12° ■ vertical measurement ■ measurement uncertainty: 1% of distance ■ needs temperature compensation ■ sensitive to snowfall and wind  Jenoptik SHM30 (laser) ■ small red laser beam ■ slanted measurement at an angle of 30° ■ measurement uncertainty: < 0.5 cm ■ no temperature compensation needed ■ insensitive to snowfall and wind Laser gauge provides backscatter signal

DWD / E. Lanzinger TECO-2010, 30. August – 1. September 2010, Helsinki, Finland Snowfall event on 23. January 2009 (Hamburg) 12:07 Onset of light / moderate snowfall 14:15 SHM 30 – snow depth > 0.5 cm 13:05 SHM 30 signal strength > :14 SR50 - snow depth ≥ 1cm SHM30 backscatter signal SHM30 snow depth SR50 (corrected 5 minute mean) wawa (Tab. 4680) Backscatter signal allows early detection of snow cover

DWD / E. Lanzinger TECO-2010, 30. August – 1. September 2010, Helsinki, Finland Operational Experience  Backscatter signal varies from gauge to gauge. Signal level should be calibrated and adjusted at the factory  Grey snow plate improves snow cover detection  Heating of housing has to be improved for icing conditions  Visible laser point can attract birds Comparison of two Laser snow depth gauges JENOPTIK SHM30. Icing problem of JENOPTIK SHM30.

DWD / E. Lanzinger TECO-2010, 30. August – 1. September 2010, Helsinki, Finland Operational Experience Very good correlation of two laser gauges and no zero drift Both laser points were about 10 cm apart

DWD / E. Lanzinger TECO-2010, 30. August – 1. September 2010, Helsinki, Finland Multipoint Measurement  Manufacturers should think about a scanning laser snow depth gauge to cover larger areas

DWD / E. Lanzinger TECO-2010, 30. August – 1. September 2010, Helsinki, Finland Thank you for your attention! Conclusions  Positive features of Laser snow depth gauges ■ Slanted measurement with high accuracy ■ Practically independent of air temperature and wind ■ No drop outs even during heavy snowfall  Detection of snow cover by backscatter signal ■ Sensitivity increased ■ Reliability of snow depth measurement increased  Possible improvements ■ Backscatter signal strength has to be calibrated ■ Multipoint measurements