Recent progress in radar-based rainfall observations over Belgium. PLURISK Final Symposium Brussels, 4 October 2017

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contributions from Lesley De Cruz, Loris Foresti, Edouard Goudenhoofdt,

1 Recent progress in radar-based rainfall observations over Belgium Laurent Delobbe Royal Meteorological Institute of Belgium with contributions from Lesley De Cruz, Loris Foresti, Edouard Goudenhoofdt, Maryna Lukach, and Maarten Reyniers PLURISK Final Symposium Brussels, 4 October 2017

2 Precipitation measurements with rain gauges Conférences 28/09/2013 2

3 More than 400 rain gauges! Courtesy of Michel Journée Several networks in Belgium: RMI AWS (15), SBGE (16), VMM (43), HIC (19), SPW (92), CLIM/SYNOP RMI/WING/BELGOCONTROL (224)

4 Which area is covered by raingauges in Belgium? 200 cm 2 x 400 = 8 m 2

5 Weather radars : more and more Jabbeke RMI Dual-pol 2012 Zaventem Belgocontrol 1974 Replaced in 2003 Helchteren VMM Dual-pol 2016 Avesnois Météo-France Dual-pol 2005 X-band Local Radars Farys-KUL Wideumont RMI 2001

6 Jabbeke and Helchteren dual-pol radars

7 Weather radars : excellent coverage of Belgium

8 Weather radar : measurement principle Typical characteristics of C-band weather radars Frequency/wavelength : 5 GHz/5 cm Pulse repetition frequency (PRF) : Pulse duration : Transmitted power : Beam width: Azimuthal resolution : Range resolution : Max detection range : μs 400 W 1.deg. 1 km at 57 km m km

Weather radar : measurement principle Typical characteristics of C-band weather radars Frequency/wavelength : 5 GHz/5 cm Pulse repetition frequency (PRF) : 800-1200

9 Weather radar : measurement principle Typical characteristics of C-band weather radars Frequency/wavelength : 5 GHz/5 cm Pulse repetition frequency (PRF) : Pulse duration : Transmitted power : Beam width: Azimuthal resolution : Range resolution : Max detection range : μs 400 W 1.deg. 1 km at 57 km m km

10 Scanning strategy Jabbeke and Wideumont radars From 3D data to 2D rainfall product Every 5 minutes 15 elevation angles Top-down From 25 to 0.3 deg. Max range JAB : 300 km WID : 250 km Z R relation 2D image «PCAPPI m»

11 Thunderstorms July 19-20, 2017 LOOP RADAR

12 Thunderstorms July 19-20, 2017.Intervention fire and rescue services (SIAMU) Radar-based rainfall amount over Brussels region Source SBGE-IRM/KMI -SIAMU Processing by Brussels Environment Courtesy of Michaël Antoine

13 Radar does not provide direct rainfall measurements From Daniel Michelson (SMHI)

14 Dual-pol based clutter removal Clutter detection using a fuzzy logic algorithm Data types: Non-polarimetric: - Z - Texture of Z - Vert. gradient of Z - V Polarimetric : - Texture of ZDR - Texture of PhiDP - RhoHV Texture = stand. deviation along range

15 Dual-pol based clutter removal Clutter detection using a fuzzy logic algorithm Data types: Non-polarimetric: - Z - Texture of Z - Vert. gradient of Z - V Polarimetric : - Texture of ZDR - Texture of PhiDP - RhoHV Texture = stand. deviation along range

16 From radar observations to rainfall amounts Removal of non-meteorological signals (interferences, ground echoes, planes, birds, ) dual-pol used when available Beam blockage and attenuation correction Stratiform-convective classification Correction based on Vertical Profile of Reflectivity Special treatment for hail Reflectivity (+ dual-pol variables) to rainfall rate Accumulation including advection correction Merging with gauges (Mean fied bias, Kriging with external drift) Combining several radars to make a composite New RMI processing chain and extended verification presented in Goudenhoofdt and Delobbe, J. Hydrometeor., 2016.

17 VPR correction Brigh band case 24h accumuation

18 10-years rainfall accumulation ( ) Basic PCAPPI QPE processing including merging with gauges r = 0.54 r = 0.80 Correlation with gauges from independent network

19 Verification 24h accum NO MERGING QPE QPE2 KED

20 Skill What is nowcasting? Detailed description of the current weather along with forecasts obtained by extrapolation for a period of 0 to 6 hours ahead (WMO definition) Radar nowcast Lead time NWP model Radar nowcast = Lagrangian extrapolation of radar rainfall images Lead time NWP : numerical weather prediction model

21 INCA-BE : operational RMI nowcasting system Radars Rain rate Hail High resolution elevation data (USGS GTOPO30) AFD INCA-BE Automatic weather stations, synop stations and regional gauge networks, RMIDB BELLS lightning data NWP (ALARO-4km) 6h update Satellite data (MSG RSS - SAFNWC) From Maarten Reyniers

22 INCA-BE nowcast : June 23, 2016

Recent progress in RMI nowcasting systems Recent progress in INCA-BE (Reyniers, ERAD 2014, 2016) Incorporation of hail and lightning Uncertainty plumes added to meteograms, takes into account unknown

23 Recent progress in RMI nowcasting systems Recent progress in INCA-BE (Reyniers, ERAD 2014, 2016) Incorporation of hail and lightning Uncertainty plumes added to meteograms, takes into account unknown evolution of motion fields Progress within PLURISK : STEPS-BE Uncertainty information associated with growth and decay of precipitation Weight RAD NWP Improved Radar-NWP blending More in the 2 next talks 2h Lead time 6h

Improvement of quantitative precipitation estimates in Belgium

Improvement of quantitative precipitation estimates in Belgium L. Delobbe, E. Goudenhoofdt, and B. Mohymont Royal Meteorological Institute of Belgium 1. Introduction In this paper we describe the recent