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Flash floods: Current practice and new developments in quantitative precipitation forecasting
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Flash floods: Current practice and new developments in quantitative precipitation forecasting

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Flash floods: Current practice and new developments in quantitative precipitation forecasting

Flash floods: Current practice and new developments in quantitative precipitation forecasting

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  • Auch RADOLAN, die Aneichung quantitativer Radarbeobachtungen an die Niederschlagsdaten von Stationsmessnetzen, wurde in Zusammenarbeit mit den für den Hochwasserschutz zuständigen Landesbehörden entwickelt. Bei diesem Verfahren liefern das Radarkomposit (16 Geräte in Deutschland) die hoch auflösenden zeitlichen und räumlichen Strukturen und die Niederschlagsmessdaten die quantitative Genauigkeit. Das RADOLAN-Verfahren wird in Echtzeit angewendet. Alle erforderlichen Daten werden umgehend nach Messung elektronisch an die Zentrale des DWD gesandt und dort ausgewertet. Die angeeichten Produkte wie das oben gezeigte stehen den Hochwasserschutzzentralen innerhalb von 20 Minuten in digitaler Form zur Verfügung. Warndienste erhalten Vorprodukte bereits innerhalb von wenigen Minuten. Neben den DWD-Messdaten werden zur Verdichtung des Gesamtnetzes auch die Daten aus den Landesmessnetzen von Bayern, Baden-Württemberg und Rheinland-Pfalz eingebunden. Vorangegangen war auch eine Abstimmung der Messnetzkonfigurationen des DWD und dieser Länder. Zur besseren quantitativen Erfassung der Niederschlagshöhe ist die Einbeziehung der Daten weiterer Länder geplant. Darüber hinaus sollen RADOLAN entsprechende Produkte für Zentraleuropa in internationaler Zusammenarbeit entwickelt werden.
  • The radar-based nowcasting procedure is based on pattern recognition in subsequent radar images and (partly) MSG. 5-min qualitative-quantitative radar images are extrapolated in 5-min steps up to max. 2 hours lead time and summed-up to hourly sums for the 2 forecast hours. Hourly sums are quantified under the presupposition of a constant frequency distribution since the latest adjustment procedure. (Method: Mapping of Weibull type of precipitation frequency distributions in forecast and latest adjusted product.) Verification of selected flood cases underway. Ongoing work: Development of methods to derive additional estimates on convective potential and phase of precipitation

Flash floods: Current practice and new developments in quantitative precipitation forecasting Flash floods: Current practice and new developments in quantitative precipitation forecasting Presentation Transcript

  • Flash floods: Current practice and new developments in quantitative precipitation forecasting Bruno Rudolf Deutscher Wetterdienst Dpt. of Hydrometeorology DWD -Dpt of Hydrometeorology, B. Rudolf – IGRC Davos 2010 1
  • Overview 1. DWD operational NWP system today 2. Limits of quantiative precipitation forecast 3. Three case studies (meteorol. flood conditions) 4. Ensemble prediction systems, future models 5. Services and summary DWD -Dpt of Hydrometeorology, B. Rudolf – IGRC Davos 2010 2
  • DWD operational NWP system Three nested models: global, Europe, Germany COSMO-DE: x = 2.8 km, 21 hours 8 runs per day COSMO-EU: x = 7 km, 78 hours 4 runs per day GME: x = 30 km, 7 days 2 runs per day DWD -Dpt of Hydrometeorology, B. Rudolf – IGRC Davos 2010 3
  • Limits of predictability Sources of the limits:  chaotic features of the atmospheric circulation  non-steady behaviour of important processes (e.g. condensation, convection and turbulence)  initial meteorological conditions are partly unknown  boundary conditions are partly unknown  the model equations are non linear on a high grade  limits of computer capacity  insuffient spatial resolution DWD -Dpt of Hydrometeorology, B. Rudolf – IGRC Davos 2010 4
  • Limits of predictability Convective cloud dynamics are not sufficiently simulated by the operational NWP models Internal structure and dynamic processes of a convective cloud system DWD -Dpt of Hydrometeorology, B. Rudolf – IGRC Davos 2010 5
  • Case 1: Elbe flood August 2002 GME LM Observations Total of 3 daily forecasts (11, 12, 13 Aug.) The large scale patterns of the precipitation totals were well predicted. • However, the high precipitation totals were considerably underestimated. DWD -Dpt of Hydrometeorology, B. Rudolf – IGRC Davos 2010 6
  • Case 2: Switzerland, Bavaria August 2005 GME LME LM Observations 24h-precip 22 to 23 August , 6:00h (model run: 22 Aug, 00 UTC) The spatial structure of daily precipitation was well predicted. • However, the spatial-temporal sequence was not yet met suffiently. DWD -Dpt of Hydrometeorology, B. Rudolf – IGRC Davos 2010 7
  • Case 3: Local flash flood 2005 ‘Millennium‘ precipitation 14:50 to 17:20 CEST RADOLAN event in Dortmund, Combination of 26 July 2008 Dortmund: radar-based and 200 mm in 2,5 h raingauge-based precipitation The probability catching observations extreme local rainfall by a raingauge is less than 10% even in a dense national network. DWD -Dpt of Hydrometeorology, B. Rudolf – IGRC Davos 2010 8
  • Case 3: Local flash flood 2005 RADOLAN COSMO-EU (7 km) COSMO-DE (2,8 km) Combination of radar model forecasts of 24 hours precipitation and gauge observation DWD -Dpt of Hydrometeorology, B. Rudolf – IGRC Davos 2010 9
  • Ensemble predictions Method: parallel numerical simulation of the same case with modified initial or boundary conditions or parametrisations within a given error range Ensemble predictions deliver: • Probalistic forecasts • Quantification of uncertainties • Risk information DWD -Dpt of Hydrometeorology, B. Rudolf – IGRC Davos 2010 10
  • Ensemble predictions COSMO-DE-EPS ensemble with 20 members for Case 3 - Dortmund 26. July 2008 hourly precipitation totals 15:00 -16:00 UTC COSMO-DE-EPS is still in development DWD -Dpt of Hydrometeorology, B. Rudolf – IGRC Davos 2010 11
  • Ensemble predictions COSMO LEPS basis ECMWF-EPS Case 2: Flood in Switzerland, Bavaria August 2005 Probability of exceeding the thresholds 50 mm precipitation Probability of 24h- precipitation > 50 mm DWD -Dpt of Hydrometeorology, B. Rudolf – IGRC Davos 2010 12
  • The future forecast models ICON ICOsahedral Non-hydrostatic General Circulation Model The grid size of the global model can be regionally improved. A first operational version is expected for autumn 2012 resolution: 20 km globaly 5 km for Europe COSMO DE is planned to be improved to 1 km spatial resolution. Ensemble applications are planned for both models. DWD -Dpt of Hydrometeorology, B. Rudolf – IGRC Davos 2010 13
  • RADVOR-OP Radar based precipitation nowcasting up to 2 hours Method: Identification and extrapolation of precipitation areas (tracking) and assessment of cell development Characteristics: Spatial resolution: 1 km Temporal resolution: 5 min / 60 min Updates every 5 minutes (The cell processing method is still in the development stage) DWD -Dpt of Hydrometeorology, B. Rudolf – IGRC Davos 2010 14
  • Communication DWD warnings in the Web Example: Case 3 (Dortmund) The text warning 26 July, 10:00 CEST: … quasi stationary convergency zone from Emsland via Northrhine-Westfalia, Rhineland- Palatinate and Saarland to the Black Forest with Heavy rainfall of more than 40 mm per hour, Hail and heavy wind gusts possible Only slow drift of the thunderstorms with direction north-west. DWD warn map published 26 July 2008, 16:48 CEST DWD -Dpt of Hydrometeorology, B. Rudolf – IGRC Davos 2010 15
  • Communication DWD Hydrometeorological services Close cooperation and joint projects of DWD and the water management authorities Provision of observational data and special forecast products tailored to the need of the water management authorities Consultancy service for water management Regular and special customer meetings Participation in relevant committees Capacity building: Education and training of the users and of students DWD -Dpt of Hydrometeorology, B. Rudolf – IGRC Davos 2010 16
  • Summary Deterministic models provide very good quantitative forecasts up to two days lead time. A 100% certainty will, however, never by possible, especially for the point in time and space of single small scale precipitation and thunderstorm events. Observational data as radar products disseminated (near) realtime provide disaster mangement with quantiative information in order to early react and to reduce damage. New technics: Ensemble forecast provide probabilities. Decision makers need to learn to use this information. DWD -Dpt of Hydrometeorology, B. Rudolf – IGRC Davos 2010 17
  • Additional material 1. Ensemble movie for Case 3 – Dortmund, 26. July 2008 hourly precipitation totals 15:00 -16:00 UTC 2. Weather chart for Case 3 – Dortmund, 26. July 2008 Convergency line as a cause of the extrem rainfall DWD -Dpt of Hydrometeorology, B. Rudolf – IGRC Davos 2010 18
  • COSMO-DE-EPS ensemble predictions with 20 members No. 1 COSMO-DE-EPS One hour precipitation total 15:00 -16:00 UTC Dortmund 26. July 2008 Method in development DWD -Dpt of Hydrometeorology, B. Rudolf – IGRC Davos 2010 19
  • COSMO-DE-EPS ensemble predictions with 20 members No. 2 COSMO-DE-EPS One hour precipitation total 15:00 -16:00 UTC Dortmund 26. July 2008 Method in development DWD -Dpt of Hydrometeorology, B. Rudolf – IGRC Davos 2010 20
  • COSMO-DE-EPS ensemble predictions with 20 members No. 3 COSMO-DE-EPS One hour precipitation total 15:00 -16:00 UTC Dortmund 26. July 2008 Method in development DWD -Dpt of Hydrometeorology, B. Rudolf – IGRC Davos 2010 21
  • COSMO-DE-EPS ensemble predictions with 20 members No. 4 COSMO-DE-EPS One hour precipitation total 15:00 -16:00 UTC Dortmund 26. July 2008 Method in development DWD -Dpt of Hydrometeorology, B. Rudolf – IGRC Davos 2010 22
  • COSMO-DE-EPS ensemble predictions with 20 members No. 5 COSMO-DE-EPS One hour precipitation total 15:00 -16:00 UTC Dortmund 26. July 2008 Method in development DWD -Dpt of Hydrometeorology, B. Rudolf – IGRC Davos 2010 23
  • COSMO-DE-EPS ensemble predictions with 20 members No. 6 COSMO-DE-EPS One hour precipitation total 15:00 -16:00 UTC Dortmund 26. July 2008 Method in development DWD -Dpt of Hydrometeorology, B. Rudolf – IGRC Davos 2010 24
  • COSMO-DE-EPS ensemble predictions with 20 members No. 7 COSMO-DE-EPS One hour precipitation total 15:00 -16:00 UTC Dortmund 26. July 2008 Method in development DWD -Dpt of Hydrometeorology, B. Rudolf – IGRC Davos 2010 25
  • COSMO-DE-EPS ensemble predictions with 20 members No. 8 COSMO-DE-EPS One hour precipitation total 15:00 -16:00 UTC Dortmund 26. July 2008 Method in development DWD -Dpt of Hydrometeorology, B. Rudolf – IGRC Davos 2010 26
  • COSMO-DE-EPS ensemble predictions with 20 members No. 9 COSMO-DE-EPS One hour precipitation total 15:00 -16:00 UTC Dortmund 26. July 2008 Method in development DWD -Dpt of Hydrometeorology, B. Rudolf – IGRC Davos 2010 27
  • COSMO-DE-EPS ensemble predictions with 20 members No. 10 COSMO-DE-EPS One hour precipitation total 15:00 -16:00 UTC Dortmund 26. July 2008 Method in development DWD -Dpt of Hydrometeorology, B. Rudolf – IGRC Davos 2010 28
  • COSMO-DE-EPS ensemble predictions with 20 members No. 11 COSMO-DE-EPS One hour precipitation total 15:00 -16:00 UTC Dortmund 26. July 2008 Method in development DWD -Dpt of Hydrometeorology, B. Rudolf – IGRC Davos 2010 29
  • COSMO-DE-EPS ensemble predictions with 20 members No. 12 COSMO-DE-EPS One hour precipitation total 15:00 -16:00 UTC Dortmund 26. July 2008 Method in development DWD -Dpt of Hydrometeorology, B. Rudolf – IGRC Davos 2010 30
  • COSMO-DE-EPS ensemble predictions with 20 members No. 13 COSMO-DE-EPS One hour precipitation total 15:00 -16:00 UTC Dortmund 26. July 2008 Method in development DWD -Dpt of Hydrometeorology, B. Rudolf – IGRC Davos 2010 31
  • COSMO-DE-EPS ensemble predictions with 20 members No. 14 COSMO-DE-EPS One hour precipitation total 15:00 -16:00 UTC Dortmund 26. July 2008 Method in development DWD -Dpt of Hydrometeorology, B. Rudolf – IGRC Davos 2010 32
  • COSMO-DE-EPS ensemble predictions with 20 members No. 15 COSMO-DE-EPS One hour precipitation total 15:00 -16:00 UTC Dortmund 26. July 2008 Method in development DWD -Dpt of Hydrometeorology, B. Rudolf – IGRC Davos 2010 33
  • COSMO-DE-EPS ensemble predictions with 20 members No. 16 COSMO-DE-EPS One hour precipitation total 15:00 -16:00 UTC Dortmund 26. July 2008 Method in development DWD -Dpt of Hydrometeorology, B. Rudolf – IGRC Davos 2010 34
  • COSMO-DE-EPS ensemble predictions with 20 members No. 17 COSMO-DE-EPS One hour precipitation total 15:00 -16:00 UTC Dortmund 26. July 2008 Method in development DWD -Dpt of Hydrometeorology, B. Rudolf – IGRC Davos 2010 35
  • COSMO-DE-EPS ensemble predictions with 20 members No. 18 COSMO-DE-EPS One hour precipitation total 15:00 -16:00 UTC Dortmund 26. July 2008 Method in development DWD -Dpt of Hydrometeorology, B. Rudolf – IGRC Davos 2010 36
  • COSMO-DE-EPS ensemble predictions with 20 members No. 19 COSMO-DE-EPS One hour precipitation total 15:00 -16:00 UTC Dortmund 26. July 2008 Method in development DWD -Dpt of Hydrometeorology, B. Rudolf – IGRC Davos 2010 37
  • COSMO-DE-EPS ensemble predictions with 20 members No. 20 COSMO-DE-EPS One hour precipitation total 15:00 -16:00 UTC Dortmund 26. July 2008 Method in development DWD -Dpt of Hydrometeorology, B. Rudolf – IGRC Davos 2010 38
  • Case 3: Local flash flood 2005 DWD Weather chart of 26. July 2008 00 UTC (02 MESZ) DWD -Dpt of Hydrometeorology, B. Rudolf – IGRC Davos 2010 39