Radar rainfall estimation of stratiform winter precipitation in the Belgian Ardennes

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Abstract. This paper presents a study on the optimal setup for discharge assimilation within a spatially distributed hydrological model. The Ensemble Kalman filter (EnKF) is employed to update the grid-based distributed states of such an hourly spatially distributed version of the HBV-96 model. By using a physically based model for the routing, the time delay and attenuation are modelled more realistically. The discharge and states at a given time step are assumed to be dependent on the previous time step only (Markov property).Synthetic and real world experiments are carried out for the Upper Ourthe (1600 km 2 ), a relatively quickly responding catchment in the Belgian Ardennes. We assess the impact on the forecasted discharge of (1) various sets of the spatially distributed discharge gauges and (2) the filtering frequency. The results show that the hydrological forecast at the catchment outlet is improved by assimilating interior gauges. This augmentation of the observation vector improves the forecast more than increasing the updating frequency. In terms of the model states, the EnKF procedure is found to mainly change the pdfs of the two routing model storages, even when the uncertainty in the discharge simulations is smaller than the defined observation uncertainty.

Section: Discussionmentioning

confidence: 99%

Section: Catchment Description and Data Availabilitymentioning

confidence: 99%

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State updating of a distributed hydrological model with Ensemble Kalman Filtering: effects of updating frequency and observation network density on forecast accuracy

Rakovec

Weerts

Hazenberg

et al. 2012

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“…6 for different partitioned state updating schemes as defined in Table 2, including both a non-augmented state (W = 0) and an augmented state (W = 11). This analysis focuses on a characteristic winter flood event (December 2002-January 2003 being typical for a moderate temperate climate caused by a fast-moving frontal stratiform system (Hazenberg et al, 2011). We observe that the ensemble of the control runs (top panel of Fig.…”

Section: The Effect Of the Four Partitioned Update Schemes And Asynchmentioning

confidence: 99%

Operational aspects of asynchronous filtering for flood forecasting

Rakovec

Weerts

Sumihar

et al. 2015

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Abstract. This study investigates the suitability of the asynchronous ensemble Kalman filter (AEnKF) and a partitioned updating scheme for hydrological forecasting. The AEnKF requires forward integration of the model for the analysis and enables assimilation of current and past observations simultaneously at a single analysis step. The results of discharge assimilation into a grid-based hydrological model (using a soil moisture error model) for the Upper Ourthe catchment in the Belgian Ardennes show that including past predictions and observations in the data assimilation method improves the model forecasts. Additionally, we show that elimination of the strongly non-linear relation between the soil moisture storage and assimilated discharge observations from the model update becomes beneficial for improved operational forecasting, which is evaluated using several validation measures.

“…Figure 5 presents a clear example of the spatial variability in the rainfall field as observed by the weather radar in De Bilt at 19:15 UTC. This weather radar scans at different elevation angles, which makes it possible to obtain a vertical profile of radar reflectivity (Hazenberg et al, 2011). In Fig.…”

Section: Synoptic Situation and Rainfall Patternmentioning

confidence: 99%

Anatomy of extraordinary rainfall and flash flood in a Dutch lowland catchment

Brauer

Teuling

Overeem

et al. 2011

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Abstract. On 26 August 2010 the eastern part of The Netherlands and the bordering part of Germany were struck by a series of rainfall events lasting for more than a day. Over an area of 740 km 2 more than 120 mm of rainfall were observed in 24 h. This extreme event resulted in local flooding of city centres, highways and agricultural fields, and considerable financial loss.In this paper we report on the unprecedented flash flood triggered by this exceptionally heavy rainfall event in the 6.5 km 2 Hupsel Brook catchment, which has been the experimental watershed employed by Wageningen University since the 1960s. This study aims to improve our understanding of the dynamics of such lowland flash floods. We present a detailed hydrometeorological analysis of this extreme event, focusing on its synoptic meteorological characteristics, its space-time rainfall dynamics as observed with rain gauges, weather radar and a microwave link, as well as the measured soil moisture, groundwater and discharge response of the catchment.At the Hupsel Brook catchment 160 mm of rainfall was observed in 24 h, corresponding to an estimated return period of well over 1000 years. As a result, discharge at the catchment outlet increased from 4.4 × 10 −3 to nearly 5 m 3 s −1 . Within 7 h discharge rose from 5 × 10 −2 to 4.5 m 3 s −1 .Correspondence to: C. C. Brauer (claudia.brauer@wur.nl)The catchment response can be divided into four phases: (1) soil moisture reservoir filling, (2) groundwater response, (3) surface depression filling and surface runoff and (4) backwater feedback. The first 35 mm of rainfall were stored in the soil without a significant increase in discharge. Relatively dry initial conditions (in comparison to those for past discharge extremes) prevented an even faster and more extreme hydrological response.