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Rainfall amount and intensity measured by the THIES Laser Precipitation Monitor

Rainfall amount and intensity measured by the THIES Laser Precipitation Monitor. Eckhard Lanzinger Manfred Theel. Herbert Windolph. Deutscher Wetterdienst (DWD) TI23 b : Measuring Systems Frahmredder 95 D-22393 Hamburg Germany email: eckhard.lanzinger@dwd.de.

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Rainfall amount and intensity measured by the THIES Laser Precipitation Monitor

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  1. Rainfall amount and intensity measured by the THIES Laser Precipitation Monitor Eckhard Lanzinger Manfred Theel Herbert Windolph Deutscher Wetterdienst (DWD) TI23 b : Measuring Systems Frahmredder 95 D-22393 Hamburg Germany email: eckhard.lanzinger@dwd.de Adolf Thies GmbH & Co. KG Hauptstraße 76 D-37083 Göttingen Germany http://www.thiesclima.com

  2. T Amplitude Diameter Duration Velocity t t Principle of operation light sheet 20 x 228 x 0.75 mm3 receiver light source aspherical lense receiver signal

  3. Factory Calibration • Optical Alignment • Beam Analyser automatically checks width, thickness and alignment of laser light sheet • Volume Calibration • automated calibration bench • precision dispensing pump • droplet generator (accuracy of diameters 2%) • x-y positioning system: 15 positions used • 2-step process: adjustment and final test Measurement uncertainty for volume measurement: 2.2%

  4. LPMOTT Pluvio DFIR GPCC gauges Pit Gauge Experiment • Wasserkuppe • ( Elevation 950 m ) • Manned Weather Station 24h operation • Reference site forGlobal PrecipitationClimate Centre • Test site for sensor intercomparisons

  5. 45 40 outlier 35 30 25 Deviation of LPM from pit gauge [mm] 20 15 +20.2% 10 +15% 5 +5.3% 0 -5 0.1 1 10 100 Reference rainfall amount (daily sums) [mm] Rainfall amount

  6. 1 Deviation of LPM from pit gauge [mm] 0.5 0 - 0.5 -1 0 0.5 1 1.5 2 Reference rainfall amount (daily sums) [mm] Rainfall amount

  7. Rainfall intensity +19.2 %+31.2 %+37.2 % LPM rainfall intensity [mm/h] Reference rainfall intensity [mm/h]

  8. Overshoots in peaks Rainfall intensity [mm/h] Rainfall intensity Typical time series

  9. Edge Correction A statistical correction has to increase the measured rainfall amount Laser light sheet

  10. LPM 3 LPM 8 LPM 9 Reference Rainfall intensity thin lines = with correction thick lines = without corr. Edge effect is over corrected.Re-Calibrationshould reducedifferencies

  11. Conclusions • The LPMs in this test generally measured too high rainfall amounts and intensities • The deviations increased with increasing intensity (overshoot) • LPM has excellent time response • LPM has very low sensitivity threshold (0.001 mm/h) and thus complements catchment type rain gauges in the low intensity range • Potential to significantly improve the measurements by • improved edge correction • improved calibration

  12. Thank you for your attention!

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