Thies Laser Precipitation Monitor for precipitation type detection

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Thies Laser Precipitation Monitor for
precipitation type detection

• H. Bloemink, E. Lanzinger
• KNMI/DWD
• 06/05/05

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Contents

• Principle
• Experiment
• Results
• Conclusions
• Recommendation

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Principle

• Disdrometer (Distribution Droplets)

• IR light beam with 45 cm² measuring area
• Extinction measurement
• amplitude diameter
• duration fall speed

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• Comparison to known statistics of diameter and
  velocity of various precipitation types
• Example
• Temperature constraints
• gt 9 C liquid (exception hail)
• lt - 4 C solid
• Output spectra, precip type, precip intensity

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Experiment

• Data from DWD test site at Wasserkuppe (Hessen)

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• Available data 12-10-2003 31-11-2003
• Observer 1 minute interval
• Reference includes T, RH, PI, wind speed,
  precip detector
• Disdrometer
• FD12P present weather sensor (current KNMI
  sensor)
• Some processing
• Precip detector used for precip/no precip
  distinction
• Time synchronisation
• Averaging

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Results

• 10-minute
• comparison

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• In terms of verification scores

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• Optimisation
• Find best possible performance using
• Averaging PW for rain snow mixtures
• Use wet-bulb temperature to distinguish freezing
  liquid precipitation
• Use wet-bulb temperature to distinguish rain and
  snow mixtures vs. Rain
• Results no improvement compared to the observer
• Possible causes
• Disdrometer tuned to Wasserkuppe conditions?
• Changes tuned to Dutch conditions FD12P

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Conclusions

• Thies disdrometer and Vaisala FD12P show similar
  results for precipitation type
• Thies slightly better for liquid, FD12P for solid
  precipitation
• Test of the Thies disdrometer in Dutch weather
  conditions
• Possible use precipitation type for smaller
  weather stations, or improved precipitation type
  by combination with FD12P

Future
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Acknowledgements
Wiel Wauben
Eckhard Lanzinger
Manfred Theel