Hazard assessment based on radar-based rainfall nowcasts at European scale The HAREN project

Transcription

1 Hazard assessment based on radar-based rainfall nowcasts at European scale The HAREN project Marc Berenguer, Daniel Sempere-Torres

2 3 OPERA radar mosaic OPERA radar mosaic: Precipitation observations over km and every minutes. Operationally produced since mid Products delivered at t+2 3 Products are available: For official duty For research and education The EU composite is not homogeneous in quality. radars 3 countries

3 3 3 Frequency of rain (dbz > dbz) in the period 1 June - 3 June ~ days 2 ~ 12 days frequency [%] ~ 6 days

4 Jun212 Dec on-going effort for improving QC frequency [%] 2 frequency [%] 2 frequency [%] 3 Oct Feb 213 May 213 Sep frequency [%] frequency [%]

5 The HAREN project The goal: Demonstrate the interest of rainfall nowcasting based on OPERA mosaics for hazard assessment. Stakeholders:

6 3 3 Radar-based rainfall nowcasting Very short-term forecasting by extrapolation of radar observations. 1.Tracking: The motion field of rainfall is estimated from observations. 2.Extrapolation: Of the most recent rainfall field. observations OBS 2/6/212 : forecasts 3

7 How does it work? -performance of nowcasting-

8 3 Nowcasting evaluation Observations 13 July : UTC Forecasts 3 3 Observed Forecasted

9 3 Nowcasting evaluation 13 July : UTC 1/e lifetime 3 Observations Forecasts 3 However, the quality of the nowcasts depends on the situation.

10 3 Evolution of the life time in the period 1 June - 31 July 212 Lifetime mostly between and h life time [h] Mean Lifetime:.h 1 Jun Jun 212 Jun Jun Jul Jul 212 Jul Jul However, the quality of the nowcasts depends on the situation.

11 3 3 Nowcasting evaluation Mean Lifetime in the period 1 June - 31 July life time:. h 3 correlation [ ] mean ACF leadtime [h]

12 3 Case Examples #1: 13 June (II) Switzerland 12 UTC nowcasts up to 8 hours Reflectivity (dbz)

13 3 Case Examples #2: 2 June (II) Switzerland 7 UTC nowcasts up to 8 hours Reflectivity (dbz)

14 3 3 Long-term evaluation in the period 1 June - 31 May 213 yearly mean LT:.2 h 3 8 life time [h] 6 2 Jun 212 Jul Aug Sep Oct Nov Dec Jan 213 Feb Mar Apr May

15 Jun212 Oct Dec life time [h] 2 life time [h] 2 life time [h] 3 Aug 212 Feb 213 Apr life time [h] life time [h]

16 Jun212 Oct Aug frequency [%] 2 2 frequency [%] 2 frequency [%] 2 3 Dec 212 Feb 213 Apr frequency [%] frequency [%]

17 Rainfall accumulation and hazard assessment

18 Forecasted rainfall accumulations

19 3 3 HAZARD ASSESSMENT based on METEOALARM thresholds Awareness type at regional scale: 3

20 3 3 HAZARD ASSESSMENT regional rainfall thresholds for 12-hour accumulations hazard level 1 hazard level 2 hazard level3 3 Countries use different accumulation windows: 1, 3, 6 and 12 hours accumulation [mm]

21 Rainfall hazard assessment

22 When is nowcasting useful? -comparison with NWP outputs-

23 3 3 ] Nowcasting vs NWP 1 June hour evaluation 3

24 3 Nowcasting vs NWP 1 June hour evaluation Comparison between rainfall forecasts and observations NWP (HIRLAM) nowcasting correlation [ ] h CN N2 EPS mean leadtime [h]

25 3 3 Conclusions Demonstration use of OPERA mosaics. Continental nowcasts benefit from the better capturing of motion at large scale and upstream coverage. Nowcasting shows average lifetime ~ hours. Very similar to the results obtained over the NEXRAD mosaic. Time and space variability: 3 Large scale systems are more predictable. Better skill in the areas with more frequent precipitation. First comparisons against operational NWP show cross-over times ~- hours. The results are clearly affected by the quality of the data being used.

26 Hazard assessment based on radar-based rainfall nowcasts at European scale - The HAREN project THANK YOU