Abstract
Abstract. The incorporation of numerical weather predictions (NWP) into a flood forecasting system can increase forecast lead times from a few hours to a few days. A single NWP forecast from a single forecast centre, however, is insufficient as it involves considerable non-predictable uncertainties and lead to a high number of false alarms. The availability of global ensemble numerical weather prediction systems through the THORPEX Interactive Grand Global Ensemble' (TIGGE) offers a new opportunity for flood forecast. The Grid-Xinanjiang distributed hydrological model, which is based on the Xinanjiang model theory and the topographical information of each grid cell extracted from the Digital Elevation Model (DEM), is coupled with ensemble weather predictions based on the TIGGE database (CMC, CMA, ECWMF, UKMO, NCEP) for flood forecast. This paper presents a case study using the coupled flood forecasting model on the Xixian catchment (a drainage area of 8826 km2) located in Henan province, China. A probabilistic discharge is provided as the end product of flood forecast. Results show that the association of the Grid-Xinanjiang model and the TIGGE database gives a promising tool for an early warning of flood events several days ahead.
Highlights
Flood protection and awareness have continued to rise on the political agenda accompanied by a drive to “improve” flood forecasts (Demeritt et al, 2007; DKKV, 2004; Parker and Fordham, 1996; Pitt, 2007; van Berkom et al, 2007; Cloke and Pappenberger, 2009)
The precipitation forecasts Pf were retrieved from five weather centres in the THORPEX Interactive Grand Global Ensemble’ (TIGGE) archive, namely Canadian Meteorological Centre (CMC), China Meteorological Administration (CMA), European Centre for Medium-Range Weather Forecasts (ECMWF), UK Met Office (UKMO), and National Centres of Environmental Prediction (NCEP)
Scores of CMA, ECMWF and NCEP, ranged from 0.46 to 0.67 for threat scores (TS) and from 0.92 to 1.49 for bias score (B) with lead times ranging from 24 h to 240 h, are slightly better than that of CMC and UKMO for small precipitation
Summary
Flood protection and awareness have continued to rise on the political agenda accompanied by a drive to “improve” flood forecasts (Demeritt et al, 2007; DKKV, 2004; Parker and Fordham, 1996; Pitt, 2007; van Berkom et al, 2007; Cloke and Pappenberger, 2009). An ensemble of weather forecasts can be used on catchment hydrology and provide improved early flood forecasting as some of the uncertainties can be quantified (Cloke and Pappenberger, 2008). To this end, a case study was carried out using five TIGGE forecast centres: The Grid-Xinanjiang model (Li et al, 2006; Wang et al, 2007; Yao et al, 2009) was used to simulate the discharge. The aims of this paper are to (1) develop atmospheric-hydrologic flood forecasting model cascade driven by TIGGE ensemble forecasts, and (2) apply the model cascade to the Xixian catchment and compare the simulation results driven by TIGGE forecasts and raingauge observation
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