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Förderprogramm des BMBF:
Risikomanagement extremer Hochwasserereignisse

Vorhersage und Management von Sturzfluten in urbanen Gebieten

Management extremer Hochwasserereignisse
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Meteorological research, Hazard analysis of precipitation

It is a well known fact, that a complete and exact record of local extreme precipitation through the usage of conventional precipitation recording systems (such as precipitation gauges and recording rain gauges) is rarely possible. New remote sensing methods such as radar or satellites are capable of locating small scale precipitation fields more exactly, however, a reliable quantitative precipitation measurement still poses a challenge and needs careful analysis of all available data. The German Weather Service (DWD) has currently developed a procedure for operational calibration of radar data to ground measurements. The procedure is still at a pre-operational test stage and will provide data at an hourly time step.

Heavy rain forecasts are currently lacking precision in location and/or volume for forecasts ranges of 30 minutes or more in convective cases. Severe storm warnings can be issued based on predicted meteorological conditions and on forecast models. However, to tell where exactly a thunderstorm is going to happen still poses a big challenge (and always will). The DWD has developed a three class warning system, however, its application comes to an end at the spatial level of a county - it often refers to several counties at a time. In general a heavy rainfall warning is given if 10 to 25mm within one hour or if 20-35mm within 6 hours are expected. Are these thresholds likely to be exceeded a heavy rainfall warning is given. There are single findings about significant local climate conditions over bigger cities and their influence on rain generation, however, so far they have not been systematically analysed for this kind of task. Future climate trends and their expected impacts on rain generation and behaviour pose another challenge to cope with.

After data processing and supply, the following issues are to be analysed within this project:

Techniques

Limits and possibilities of various techniques for recording of local and short-term extreme precipitation

  • Quality inspection of conventional meteorological network (which is a basis for KOSTRA and hazard analysis) concerning the real precipitation intensity during shower events (e.g. a thunder-storm cell only touches a rain gauge)
  • Localisation of thunderstorm cells with extreme precipitation in urban areas by using the KONRAD cell tracking method
  • Experimental resolution upgrade of radar data from 1 km up to 250 m

Event types

Flash flood characterisation depending on flash flood type by using selected case studies

  • Analysis of local extreme precipitation, its typical course and behaviour depending on type, region and urban structure
  • Analysis of meteorological characteristics for flash flood producing rainfall, cause study by using selected flash flood events
  • Relief driven impacts on local convective storm generation (luff, lee, foehn etc.) close to urban areas
  • Does the selected metropolitan area itself have an impact on flash flood generation (involvement of sferics records)?

Risk areas

Statistic approach to assess risk areas struck by flash floods

  • Extreme value analysis of local extreme precipitation events using conventional ground records: does climate change have an impact on frequency or intensity of flash flood triggering precipitation? (contractual duties)
  • Approach to climatic analysis of radar data: detection of typical thunderstorm tracks using KONRAD. As a result a map is expected to localize regions frequently struck by extreme precipitation and detected by KONRAD

Forecast

Investigations are to be made about current state-of-the-art forecast of local extreme precipitation (including nowcasting)

  • Further development of such methods focuses on the existing system KONRAD, which is to be expanded to be able to give warnings of heavy rainfalls. Applicability of data and systems for KONRAD and RADVOR_OP is to be specified for this kind of task.
  • Knowledge gained will be used within the DWD, e.g. data about tracking of thunderstorm cells can be also used for a forecast model. The operational application of the intended (projected) second warning stage for heavy rainfall within KONRAD could provide an opportunity to introduce a warning system such as FEWIS (fire brigade information system) to municipalities.
 

gefördert durch: Projekträger: Projektpartner:
Logo des Bundesministerium für Bildung und Forschung Logo PTJ - Projekträger Jülich Hydrotec Logo DWD Logo Logo der FH Aachen
Kooperationspartner:
Logo der Hansestadt Hamburg Logo der Deutsche Rückversicherung GmbH Logo des Stadtentwässerungsbetriebs Paderborn
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