Journal cover Journal topic
Hydrology and Earth System Sciences An interactive open-access journal of the European Geosciences Union
doi:10.5194/hess-2017-150
© Author(s) 2017. This work is distributed
under the Creative Commons Attribution 3.0 License.
Research article
02 May 2017
Review status
This discussion paper is under review for the journal Hydrology and Earth System Sciences (HESS).
At-site and regional frequency analysis of extreme precipitation from radar-based estimates
Edouard Goudenhoofdt1, Laurent Delobbe1, and Patrick Willems2 1The Royal Meteorological Institute of Belgium, Brussels, Belgium
2Department of Civil Engineering - Hydraulics Division, University of Leuven, Leuven, Belgium
Abstract. In Belgium, only rain gauge time-series have been used so far to study extreme precipitation at a given location. In this paper, the potential of a 12-year quantitative precipitation estimation (QPE) from a single weather radar is evaluated. For the period 2005–2016, independent sliding 1 h and 24 h rainfall extremes from automatic rain gauges and collocated radar estimates are compared. The extremes are fitted to the exponential distribution using regression in QQ-plots with a threshold rank which minimises the mean squared error. A basic radar product used as reference exhibits unrealistic high extremes and is not suitable for extreme value analysis. For 24 h rainfall extremes, which occur partly in winter, the radar-based QPE needs a bias correction. A few missing events are caused by the wind drift of convective cells and strong radar signal attenuation. Differences between radar and gauge values are caused by spatial and temporal sampling, gauge rainfall underestimations and radar errors due to the relation between reflectivity and rain rate. Nonetheless the fit to the QPE data is within the confidence interval of the gauge fit, which remains large due to the short study period. A regional frequency analysis is performed on radar data within 20 km of the locations of 4 rain gauges with records from 1965 to 2008. Assuming that the extremes are correlated within the region, the fit to the two closest rain gauge data is within the confidence interval of the radar fit, which is small due to the sample size. In Brussels, the extremes on the period 1965–2008 from a rain gauge are significantly lower than the extremes from an automatic gauge and the radar on the period 2005–2016. For 1 h duration, the location parameter varies slightly with topography and the scale parameter exhibits some variations from region to region. The radar-based extreme value analysis can be extended to other durations.

Citation: Goudenhoofdt, E., Delobbe, L., and Willems, P.: At-site and regional frequency analysis of extreme precipitation from radar-based estimates, Hydrol. Earth Syst. Sci. Discuss., doi:10.5194/hess-2017-150, in review, 2017.
Edouard Goudenhoofdt et al.
Edouard Goudenhoofdt et al.
Edouard Goudenhoofdt et al.

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Short summary
Knowing the characterisitcs of extreme precipitation is useful for flood management applications like sewer system design. The potential of a 12-years high-quality weather radar precipitation dataset is investigated by comparison with rain gauges. Despite known limitations a good agreement is found between the radar and the rain gauges. Using the radar data allow to reduce the uncertainty of the exteme value analysis especially for short duration extremes related to thunderstorms.
Knowing the characterisitcs of extreme precipitation is useful for flood management applications...
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