Hazard assessment based on radar-based rainfall nowcasts at European scale The HAREN project Marc Berenguer, Daniel Sempere-Torres
3 OPERA radar mosaic OPERA radar mosaic: 213919 133 Precipitation observations over Europe @2 km and every minutes. Operationally produced since mid 211. 3 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 Frequency of rain (dbz > dbz) in the period 1 June - 3 June 213 3 2 ~ days 2 ~ 12 days frequency [%] ~ 6 days
Jun212 Dec 212 1 2 2 2 2 2 2 on-going effort for improving QC frequency [%] 2 frequency [%] 2 frequency [%] 3 Oct 212 3 Feb 213 May 213 Sep 213 2 2 2 2 2 2 3 frequency [%] frequency [%]
The HAREN project The goal: Demonstrate the interest of rainfall nowcasting based on OPERA mosaics for hazard assessment. Stakeholders:
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
How does it work? -performance of nowcasting-
3 Nowcasting evaluation Observations 13 July 212 21: UTC Forecasts 3 3 Observed Forecasted
3 Nowcasting evaluation 13 July 212 21: UTC 1/e lifetime 3 Observations Forecasts 3 However, the quality of the nowcasts depends on the situation.
3 Evolution of the life time in the period 1 June - 31 July 212 Lifetime mostly between and h 2 2 3 life time [h] Mean Lifetime:.h 1 Jun 212 1 8 Jun 212 Jun 212 22 Jun 212 1 Jul 212 8 Jul 212 Jul 212 22 Jul 212 3 However, the quality of the nowcasts depends on the situation.
3 3 Nowcasting evaluation Mean Lifetime in the period 1 June - 31 July 212 1..8 life time:. h 3 correlation [ ].6. 2.2 1 mean ACF. 2 6 8 leadtime [h]
3 Case Examples #1: 13 June (II) - 212 Switzerland 12 UTC nowcasts up to 8 hours 3 3 2 2 3 3 6 6 7 Reflectivity (dbz)
3 Case Examples #2: 2 June (II) - 212 Switzerland 7 UTC nowcasts up to 8 hours 3 3 2 2 3 3 6 6 7 Reflectivity (dbz)
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
Jun212 Oct 212 1 2 3 Dec 212 2 life time [h] 2 life time [h] 2 life time [h] 3 Aug 212 Feb 213 Apr 213 2 2 2 3 life time [h] life time [h]
Jun212 Oct 212 1 3 Aug 212 2 2 2 2 frequency [%] 2 2 frequency [%] 2 frequency [%] 2 3 Dec 212 Feb 213 Apr 213 2 2 2 2 2 2 3 frequency [%] frequency [%]
Rainfall accumulation and hazard assessment
Forecasted rainfall accumulations
3 3 HAZARD ASSESSMENT based on METEOALARM thresholds Awareness type at regional scale: 3
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. 1 7 2 accumulation [mm]
Rainfall hazard assessment
When is nowcasting useful? -comparison with NWP outputs-
3 3 ] Nowcasting vs NWP 1 June 213-8 hour evaluation 3
3 Nowcasting vs NWP 1 June 213-8 hour evaluation Comparison between rainfall forecasts and observations NWP (HIRLAM) nowcasting 1. 3.8 correlation [ ].6..2. 3 8h CN N2 EPS mean 12 2 36 8 leadtime [h]
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.
Hazard assessment based on radar-based rainfall nowcasts at European scale - The HAREN project THANK YOU www.haren-project.eu/workshop