Thies Laser Precipitation Monitor for precipitation type detection

Thies Laser Precipitation Monitor for precipitation type detection H. Bloemink, E. Lanzinger KNMI/DWD 06/05/05

Contents l l l Principle Experiment Results Conclusions Recommendation

Principle l Disdrometer (Distribution Droplets) n. IR light beam with 45 cm² measuring area n. Extinction measurement n amplitude: diameter n duration: fall speed

l Comparison to known statistics of diameter and velocity of various precipitation types Example: l Temperature constraints: l l > 9 °C: liquid (exception: hail) < - 4 °C: solid Output: spectra, precip type, precip intensity

Experiment l Data from DWD test site at Wasserkuppe (Hessen)

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

Results l 10 -minute comparison

l In terms of verification scores:

l Optimisation l Find best possible performance using l l l 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: l l Disdrometer tuned to Wasserkuppe conditions? Changes tuned to Dutch conditions & FD 12 P

Conclusions l l Thies disdrometer and Vaisala FD 12 P show similar results for precipitation type Thies slightly better for liquid, FD 12 P for solid precipitation Future l l Test of the Thies disdrometer in Dutch weather conditions Possible use: precipitation type for smaller weather stations, or improved precipitation type by combination with FD 12 P

Acknowledgements Manfred Theel Wiel Wauben Eckhard Lanzinger