German Weather Service Rainfall amount and intensity measured

German Weather Service Rainfall amount and intensity measured by the THIES Laser Precipitation Monitor Eckhard Lanzinger Manfred Theel Herbert Windolph Deutscher Wetterdienst (DWD) TI 23 b : Measuring Systems Frahmredder 95 D-22393 Hamburg Germany email: eckhard. lanzinger@dwd. de TECO-2006, Geneva, 05. 12. 2006 Adolf Thies Gmb. H & Co. KG Hauptstraße 76 D-37083 Göttingen Germany http: //www. thiesclima. com 1 Rainfall amount & intensity with THIES LPM / DWD / E. Lanzinger

German Weather Service Principle of operation light sheet 20 x 228 x 0. 75 mm 3 receiver light source aspherical lense T Amplitude Duration receiver signal t TECO-2006, Geneva, 05. 12. 2006 2 Diameter Velocity Rainfall amount & intensity with THIES LPM / DWD / E. Lanzinger

German Weather Service 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% TECO-2006, Geneva, 05. 12. 2006 3 Rainfall amount & intensity with THIES LPM / DWD / E. Lanzinger

German Weather Service Experiment Wasserkuppe ( Elevation 950 m ) • Manned Weather Station 24 h operation LPM OTT Pluvio • Reference site for Global Precipitation Climate Centre • Test site for sensor intercomparisons TECO-2006, Geneva, 05. 12. 2006 GPCC gauges DFIR Pit Gauge 4 Rainfall amount & intensity with THIES LPM / DWD / E. Lanzinger

German Weather Service Rainfall amount Deviation of LPM from pit gauge [mm] 45 40 30 25 20 15 +20. 2% 10 +15% 5 +5. 3% 0 -5 0. 1 TECO-2006, Geneva, 05. 12. 2006 outlier 35 1 10 Reference rainfall amount (daily sums) [mm] 5 100 Rainfall amount & intensity with THIES LPM / DWD / E. Lanzinger

German Weather Service Deviation of LPM from pit gauge [mm] Rainfall amount 1 0. 5 0 - 0. 5 -1 TECO-2006, Geneva, 05. 12. 2006 0 0. 5 1 1. 5 Reference rainfall amount (daily sums) [mm] 6 2 Rainfall amount & intensity with THIES LPM / DWD / E. Lanzinger

German Weather Service Rainfall intensity LPM rainfall intensity [mm/h] +19. 2 % +31. 2 % +37. 2 % Reference rainfall intensity [mm/h] TECO-2006, Geneva, 05. 12. 2006 7 Rainfall amount & intensity with THIES LPM / DWD / E. Lanzinger

German Weather Service Rainfall intensity [mm/h] Typical time series Overshoots in peaks TECO-2006, Geneva, 05. 12. 2006 8 Rainfall amount & intensity with THIES LPM / DWD / E. Lanzinger

German Weather Service Edge Correction A statistical correction has to increase the measured rainfall amount Laser light sheet TECO-2006, Geneva, 05. 12. 2006 9 Rainfall amount & intensity with THIES LPM / DWD / E. Lanzinger

German Weather Service Rainfall intensity thin lines = with correction LPM 3 thick lines = without corr. LPM 8 LPM 9 Reference Edge effect is over corrected. Re-Calibration should reduce differencies TECO-2006, Geneva, 05. 12. 2006 10 Rainfall amount & intensity with THIES LPM / DWD / E. Lanzinger

German Weather Service 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 TECO-2006, Geneva, 05. 12. 2006 11 Rainfall amount & intensity with THIES LPM / DWD / E. Lanzinger

German Weather Service Thank you for your attention! TECO-2006, Geneva, 05. 12. 2006 12 Rainfall amount & intensity with THIES LPM / DWD / E. Lanzinger