URBAS Radar—an approach to flash flood statistics

In densely populated Germany, flash floods lead to comparable damage as river flooding. Forecast and warning, however, is difficult. Further, there is a lack of hazard maps for this kind of event due to its small scale nature, short lead time and rareness. Under the URBAS project (“forecast and management of flash floods in urban areas”) funded by the German Federal Ministry of Education and Research (BMBF), a team of hydrologists, meteorologists and specialists for urban development analyse case studies of flash floods in close cooperation with several municipalities and cities throughout Germany to address this problem.

The sub-project URBAS_Radar is involved in all meteorological aspects of this project. Its focus is a statistical approach to radar climatology of intense precipitation and convective rain events. DWD's warning tool CONRAD (CONvection in RADar data) features cell identification and ~ tracking mechanisms and a variety of warnings such as hail, severe convection, intense precipitation etc. This additional information about the point of origin or genesis of convective cells should help to improve warning systems. Within this project, the coincidence of areal meteorological hazards (based on statistics) and of flash floods in urban areas (based on case studies and local situations) shall be investigated.

Seven years of local CONRAD data of all 16 weather radars in Germany from 2000 to 2006 is examined, therefore. Detailed analysis is carried out on individual radars, results are composited.

First results are promising. Even without corrections, clusters of intense precipitation or preferred tracks of convective cells within one radar ambit become apparent. Corrections are mainly necessary for quantitative comparisons among different radar ranges or radar sites. A mixture of statistical modifications and interpolations of radar data is being used.