Transcript German Weather Service 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.

German Weather Service
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: [email protected]
TECO-2006, Geneva, 05.12.2006
Adolf Thies GmbH & Co. KG
Hauptstraße 76
D-37083 Göttingen
Germany
http://www.thiesclima.com
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Rainfall amount & intensity with THIES LPM / DWD / E. Lanzinger
German Weather Service
Principle of operation
light sheet
20 x 228 x 0.75 mm3
receiver
light source
aspherical lense
T
receiver signal
t
TECO-2006, Geneva, 05.12.2006
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Amplitude
Diameter
Duration
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
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Rainfall amount & intensity with THIES LPM / DWD / E. Lanzinger
German Weather Service
Experiment
Wasserkuppe
( Elevation 950 m )
• Manned Weather Station
24h operation
LPM
OTT Pluvio
• Reference site for
Global Precipitation
Climate Centre
• Test site for sensor
intercomparisons
TECO-2006, Geneva, 05.12.2006
DFIR
GPCC
gauges
Pit Gauge
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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
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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
0
TECO-2006, Geneva, 05.12.2006
0.5
1
1.5
Reference rainfall amount (daily sums) [mm]
6
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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]
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Rainfall amount & intensity with THIES LPM / DWD / E. Lanzinger
German Weather Service
Rainfall
intensity
Rainfall intensity [mm/h]
Typical
time series
Overshoots in
peaks
TECO-2006, Geneva, 05.12.2006
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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
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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
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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
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Rainfall amount & intensity with THIES LPM / DWD / E. Lanzinger
German Weather Service
Thank you for your attention!
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Rainfall amount & intensity with THIES LPM / DWD / E. Lanzinger